some cleanup and annonce expiry

.dockerignore

@@ -0,0 +1,68 @@
+# .dockerignore for go-cart-actor
+#
+# Goal: Keep Docker build context lean & reproducible.
+# Adjust as project structure evolves.
+
+# Version control & CI metadata
+.git
+.git/
+.gitignore
+.github
+
+# Local tooling / editors
+.vscode
+.idea
+*.iml
+
+# Build artifacts / outputs
+bin/
+build/
+dist/
+out/
+coverage/
+*.coverprofile
+
+# Temporary files
+*.tmp
+*.log
+tmp/
+.tmp/
+
+# Dependency/vendor caches (not used; rely on go modules download)
+vendor/
+
+# Examples / scripts (adjust if you actually need them in build context)
+examples/
+scripts/
+
+# Docs (retain README.md explicitly)
+docs/
+CHANGELOG*
+**/*.md
+!README.md
+
+# Tests (not needed for production build)
+**/*_test.go
+
+# Node / frontend artifacts (if any future addition)
+node_modules/
+
+# Docker / container metadata not needed inside image
+Dockerfile
+
+# Editor swap/backup files
+*~
+*.swp
+
+# Go race / profiling outputs
+*.pprof
+
+# Security / secret placeholders (ensure real secrets never copied)
+*.secret
+*.key
+*.pem
+
+# Keep proto and generated code (do NOT ignore proto/)
+!proto/
+
+# End of file

.gitea/workflows/build.yaml

@@ -1,30 +1,77 @@
 name: Build and Publish
-run-name: ${{ gitea.actor }} is building 🚀
+run-name: ${{ gitea.actor }} build 🚀
 on: [push]
 
 jobs:
-  BuildAndDeployAmd64:
-    runs-on: amd64
-    steps:
-      - name: Check out repository code
-        uses: actions/checkout@v4
-      - name: Build docker image
-        run: docker build --progress=plain -t registry.knatofs.se/go-cart-actor-amd64:latest .
-      - name: Push to registry
-        run: docker push registry.knatofs.se/go-cart-actor-amd64:latest
-      - name: Deploy to Kubernetes
-        run: kubectl apply -f deployment/deployment.yaml -n cart
-      - name: Rollout amd64 deployment
-        run: kubectl rollout restart deployment/cart-actor-x86 -n cart
-  
-  BuildAndDeploy:
-    runs-on: arm64
-    steps:
-      - name: Check out repository code
-        uses: actions/checkout@v4
-      - name: Build docker image
-        run: docker build --progress=plain -t registry.knatofs.se/go-cart-actor .
-      - name: Push to registry
-        run: docker push registry.knatofs.se/go-cart-actor
-      - name: Rollout arm64 deployment
-        run: kubectl rollout restart deployment/cart-actor-arm64 -n cart
+    Metadata:
+        runs-on: arm64
+        outputs:
+            version: ${{ steps.meta.outputs.version }}
+            git_commit: ${{ steps.meta.outputs.git_commit }}
+            build_date: ${{ steps.meta.outputs.build_date }}
+        steps:
+            - name: Checkout
+              uses: actions/checkout@v4
+            - id: meta
+              name: Derive build metadata
+              run: |
+                  GIT_COMMIT=$(git rev-parse HEAD)
+                  if git describe --tags --exact-match >/dev/null 2>&1; then
+                    VERSION=$(git describe --tags --exact-match)
+                  else
+                    VERSION=$(git rev-parse --short=12 HEAD)
+                  fi
+                  BUILD_DATE=$(date -u +"%Y-%m-%dT%H:%M:%SZ")
+                  echo "git_commit=$GIT_COMMIT" >> $GITHUB_OUTPUT
+                  echo "version=$VERSION" >> $GITHUB_OUTPUT
+                  echo "build_date=$BUILD_DATE" >> $GITHUB_OUTPUT
+
+    BuildAndDeployAmd64:
+        needs: Metadata
+        runs-on: amd64
+        steps:
+            - uses: actions/checkout@v4
+            - name: Build amd64 image
+              run: |
+                  docker build \
+                    --build-arg VERSION=${{ needs.Metadata.outputs.version }} \
+                    --build-arg GIT_COMMIT=${{ needs.Metadata.outputs.git_commit }} \
+                    --build-arg BUILD_DATE=${{ needs.Metadata.outputs.build_date }} \
+                    --progress=plain \
+                    -t registry.knatofs.se/go-cart-actor-amd64:latest \
+                    -t registry.knatofs.se/go-cart-actor-amd64:${{ needs.Metadata.outputs.version }} \
+                    .
+            - name: Push amd64 images
+              run: |
+                  docker push registry.knatofs.se/go-cart-actor-amd64:latest
+                  docker push registry.knatofs.se/go-cart-actor-amd64:${{ needs.Metadata.outputs.version }}
+            - name: Apply deployment manifests
+              run: kubectl apply -f deployment/deployment.yaml -n cart
+            - name: Rollout amd64 deployment (pin to version)
+              run: |
+                  kubectl set image deployment/cart-actor-x86 -n cart cart-actor-amd64=registry.knatofs.se/go-cart-actor-amd64:${{ needs.Metadata.outputs.version }}
+                  kubectl rollout status deployment/cart-actor-x86 -n cart
+
+    BuildAndDeployArm64:
+        needs: Metadata
+        runs-on: arm64
+        steps:
+            - uses: actions/checkout@v4
+            - name: Build arm64 image
+              run: |
+                  docker build \
+                    --build-arg VERSION=${{ needs.Metadata.outputs.version }} \
+                    --build-arg GIT_COMMIT=${{ needs.Metadata.outputs.git_commit }} \
+                    --build-arg BUILD_DATE=${{ needs.Metadata.outputs.build_date }} \
+                    --progress=plain \
+                    -t registry.knatofs.se/go-cart-actor:latest \
+                    -t registry.knatofs.se/go-cart-actor:${{ needs.Metadata.outputs.version }} \
+                    .
+            - name: Push arm64 images
+              run: |
+                  docker push registry.knatofs.se/go-cart-actor:latest
+                  docker push registry.knatofs.se/go-cart-actor:${{ needs.Metadata.outputs.version }}
+            - name: Rollout arm64 deployment (pin to version)
+              run: |
+                  kubectl set image deployment/cart-actor-arm64 -n cart cart-actor-arm64=registry.knatofs.se/go-cart-actor:${{ needs.Metadata.outputs.version }}
+                  kubectl rollout status deployment/cart-actor-arm64 -n cart

Dockerfile

@@ -1,17 +1,75 @@
-# syntax=docker/dockerfile:1
+# syntax=docker/dockerfile:1.7
+#
+# Multi-stage build:
+#  1. Build static binary with pinned Go version (matching go.mod).
+#  2. Copy into distroless static nonroot runtime image.
+#
+# Build args (optional):
+#   VERSION      - semantic/app version (default: dev)
+#   GIT_COMMIT   - git SHA (default: unknown)
+#   BUILD_DATE   - RFC3339 build timestamp
+#
+# Example build:
+#   docker build \
+#     --build-arg VERSION=$(git describe --tags --always) \
+#     --build-arg GIT_COMMIT=$(git rev-parse HEAD) \
+#     --build-arg BUILD_DATE=$(date -u +%Y-%m-%dT%H:%M:%SZ) \
+#     -t go-cart-actor:dev .
+#
+# If you add subpackages or directories, no Dockerfile change needed (COPY . .).
+# Ensure a .dockerignore exists to keep context lean.
 
-FROM golang:alpine AS build-stage
-WORKDIR /app
+############################
+# Build Stage
+############################
+FROM golang:1.25-alpine AS build
+WORKDIR /src
+
+# Build metadata (can be overridden at build time)
+ARG VERSION=dev
+ARG GIT_COMMIT=unknown
+ARG BUILD_DATE=unknown
+
+# Ensure reproducible static build
+# Multi-arch build args (TARGETOS/TARGETARCH provided automatically by buildx)
+ARG TARGETOS
+ARG TARGETARCH
+ENV CGO_ENABLED=0 GOOS=${TARGETOS:-linux} GOARCH=${TARGETARCH}
+
+# Dependency caching
 COPY go.mod go.sum ./
-RUN go mod download
+RUN --mount=type=cache,target=/go/pkg/mod \
+    go mod download
 
-COPY proto ./proto
-COPY *.go ./
+# Copy full source (relay on .dockerignore to prune)
+COPY . .
 
-RUN CGO_ENABLED=0 GOOS=linux go build -o /go-cart-actor
+# (Optional) If you do NOT check in generated protobuf code, uncomment generation:
+# RUN go install google.golang.org/protobuf/cmd/protoc-gen-go@latest && \
+#     go install google.golang.org/grpc/cmd/protoc-gen-go-grpc@latest && \
+#     protoc --go_out=. --go_opt=paths=source_relative \
+#            --go-grpc_out=. --go-grpc_opt=paths=source_relative \
+#            proto/*.proto
 
-FROM gcr.io/distroless/base-debian11
+# Build with minimal binary size and embedded metadata
+RUN --mount=type=cache,target=/go/build-cache \
+    go build -trimpath -ldflags="-s -w \
+      -X main.Version=${VERSION} \
+      -X main.GitCommit=${GIT_COMMIT} \
+      -X main.BuildDate=${BUILD_DATE}" \
+      -o /out/go-cart-actor .
+
+############################
+# Runtime Stage
+############################
+# Using distroless static (nonroot) for minimal surface area.
+FROM gcr.io/distroless/static-debian12:nonroot AS runtime
 WORKDIR /
 
-COPY --from=build-stage /go-cart-actor /go-cart-actor
-ENTRYPOINT ["/go-cart-actor"]
+COPY --from=build /out/go-cart-actor /go-cart-actor
+
+# Document (not expose forcibly) typical ports: 8080 (HTTP), 1337 (gRPC)
+EXPOSE 8080 1337
+
+USER nonroot:nonroot
+ENTRYPOINT ["/go-cart-actor"]

GRPC-MIGRATION-PLAN.md

@@ -1,396 +0,0 @@
-# gRPC Migration Plan
-
-File: GRPC-MIGRATION-PLAN.md  
-Author: (Generated plan)  
-Status: Draft for review  
-Target Release: Next major version (breaking change – no mixed compatibility)
-
----
-
-## 1. Overview
-
-This document describes the full migration of the current custom TCP frame-based protocol (both the cart mutation/state channel on port `1337` and the control plane on port `1338`) to gRPC. We will remove all legacy packet framing (`FrameWithPayload`, `RemoteGrain`, `GenericListener` handlers for these two ports) and replace them with two gRPC services:
-
-1. Cart Actor Service (mutations + state retrieval)
-2. Control Plane Service (cluster membership, negotiation, ownership change, lifecycle)
-
-We intentionally keep:
-- Internal `CartGrain` logic, message storage format, disk persistence, and JSON cart serialization.
-- Existing message type numeric mapping for backward compatibility with persisted event logs.
-- HTTP/REST API layer unchanged (it still consumes JSON state from the local/remote grain pipeline).
-
-We do NOT implement mixed-version compatibility; migration occurs atomically (cluster restart with new image).
-
----
-
-## 2. Goals
-
-- Remove custom binary frame protocol & simplify maintenance.
-- Provide clearer, strongly defined interfaces via `.proto` schemas.
-- Improve observability via gRPC interceptors (metrics & tracing hooks).
-- Reduce per-call overhead compared with the current manual connection pooling + handwritten framing (HTTP/2 multiplexing + connection reuse).
-- Prepare groundwork for future enhancements (streaming, typed state, event streaming) without rewriting again.
-
----
-
-## 3. Non-Goals (Phase 1)
-
-- Converting the cart state payload from JSON to a strongly typed proto.
-- Introducing authentication / mTLS (may be added later).
-- Changing persistence or replay format.
-- Changing the HTTP API contract.
-- Implementing streaming watchers or push updates.
-
----
-
-## 4. Architecture After Migration
-
-Ports:  
-- `:1337` → gRPC CartActor service.  
-- `:1338` → gRPC ControlPlane service.
-
-Each node:
-- Runs one gRPC server with both services (can use a single listener bound to two services or keep two separate listeners; we will keep two ports initially to minimize operational surprise, but they could be merged later).
-- Maintains a connection pool of `*grpc.ClientConn` objects keyed by remote hostname (one per remote host, reused for both services).
-
-Call Flow (Mutation):
-1. HTTP request hits `PoolServer`.
-2. `SyncedPool.getGrain(cartId)`:
-   - Local: direct invocation.
-   - Remote: uses `RemoteGrainGRPC` (new) which invokes `CartActor.Mutate`.
-3. Response JSON returned unchanged.
-
-Control Plane Flow:
-- Discovery (K8s watch) still triggers `AddRemote(host)`.
-- Instead of custom `Ping`, `Negotiate`, etc. via frames, call gRPC methods on `ControlPlane` service.
-- Ownership changes use `ConfirmOwner` RPC.
-
----
-
-## 5. Proto Design
-
-### 5.1 Cart Actor Proto (Envelope Pattern)
-
-We keep an envelope with `bytes payload` holding the serialized underlying cart mutation proto (existing types in `messages.proto`). This minimizes churn.
-
-Indented code block (proto sketch):
-
-    syntax = "proto3";
-    package cart;
-    option go_package = "git.tornberg.me/go-cart-actor/proto;proto";
-
-    enum MutationType {
-      MUTATION_TYPE_UNSPECIFIED = 0;
-      MUTATION_ADD_REQUEST = 1;
-      MUTATION_ADD_ITEM = 2;
-      MUTATION_REMOVE_ITEM = 4;
-      MUTATION_REMOVE_DELIVERY = 5;
-      MUTATION_CHANGE_QUANTITY = 6;
-      MUTATION_SET_DELIVERY = 7;
-      MUTATION_SET_PICKUP_POINT = 8;
-      MUTATION_CREATE_CHECKOUT_ORDER = 9;
-      MUTATION_SET_CART_ITEMS = 10;
-      MUTATION_ORDER_COMPLETED = 11;
-    }
-
-    message MutationRequest {
-      string cart_id = 1;
-      MutationType type = 2;
-      bytes payload = 3;          // Serialized specific mutation proto
-      int64 client_timestamp = 4; // Optional; server fills if zero
-    }
-
-    message MutationReply {
-      int32 status_code = 1;
-      bytes payload = 2; // JSON cart state or error string
-    }
-
-    message StateRequest {
-      string cart_id = 1;
-    }
-
-    message StateReply {
-      int32 status_code = 1;
-      bytes payload = 2; // JSON cart state
-    }
-
-    service CartActor {
-      rpc Mutate(MutationRequest) returns (MutationReply);
-      rpc GetState(StateRequest) returns (StateReply);
-    }
-
-### 5.2 Control Plane Proto
-
-    syntax = "proto3";
-    package control;
-    option go_package = "git.tornberg.me/go-cart-actor/proto;proto";
-
-    message Empty {}
-
-    message PingReply {
-      string host = 1;
-      int64 unix_time = 2;
-    }
-
-    message NegotiateRequest {
-      repeated string known_hosts = 1;
-    }
-    message NegotiateReply {
-      repeated string hosts = 1; // Healthy hosts returned
-    }
-
-    message CartIdsReply {
-      repeated string cart_ids = 1;
-    }
-
-    message OwnerChangeRequest {
-      string cart_id = 1;
-      string new_host = 2;
-    }
-    message OwnerChangeAck {
-      bool accepted = 1;
-      string message = 2;
-    }
-
-    message ClosingNotice {
-      string host = 1;
-    }
-
-    service ControlPlane {
-      rpc Ping(Empty) returns (PingReply);
-      rpc Negotiate(NegotiateRequest) returns (NegotiateReply);
-      rpc GetCartIds(Empty) returns (CartIdsReply);
-      rpc ConfirmOwner(OwnerChangeRequest) returns (OwnerChangeAck);
-      rpc Closing(ClosingNotice) returns (OwnerChangeAck);
-    }
-
----
-
-## 6. Message Type Mapping
-
-| Legacy Constant | Numeric | New Enum Value              |
-|-----------------|---------|-----------------------------|
-| AddRequestType  | 1       | MUTATION_ADD_REQUEST        |
-| AddItemType     | 2       | MUTATION_ADD_ITEM           |
-| RemoveItemType  | 4       | MUTATION_REMOVE_ITEM        |
-| RemoveDeliveryType | 5    | MUTATION_REMOVE_DELIVERY    |
-| ChangeQuantityType | 6    | MUTATION_CHANGE_QUANTITY    |
-| SetDeliveryType | 7       | MUTATION_SET_DELIVERY       |
-| SetPickupPointType | 8    | MUTATION_SET_PICKUP_POINT   |
-| CreateCheckoutOrderType | 9 | MUTATION_CREATE_CHECKOUT_ORDER |
-| SetCartItemsType | 10     | MUTATION_SET_CART_ITEMS     |
-| OrderCompletedType | 11   | MUTATION_ORDER_COMPLETED    |
-
-Persisted events keep original numeric codes; reconstruction simply casts to `MutationType`.
-
----
-
-## 7. Components To Remove / Replace
-
-Remove (after migration complete):
-- `remote-grain.go`
-- `rpc-server.go`
-- Any packet/frame-specific types solely used by the above (search: `FrameWithPayload`, `RemoteHandleMutation`, `RemoteGetState` where not reused by disk or internal logic).
-- The constants representing network frame types in `synced-pool.go` (RemoteNegotiate, AckChange, etc.) replaced by gRPC calls.
-- netpool usage for remote cart channel (control plane also no longer needs `Connection` abstraction).
-
-Retain (until reworked or optionally cleaned later):
-- `message.go` (for persistence)
-- `message-handler.go`
-- `cart-grain.go`
-- `messages.proto` (underlying mutation messages)
-- HTTP API server and REST handlers.
-
----
-
-## 8. New / Modified Components
-
-New files (planned):
-- `proto/cart_actor.proto`
-- `proto/control_plane.proto`
-- `grpc/cart_actor_server.go` (server impl)
-- `grpc/cart_actor_client.go` (client adapter implementing `Grain`)
-- `grpc/control_plane_server.go`
-- `grpc/control_plane_client.go`
-- `grpc/interceptors.go` (metrics, logging, optional tracing hooks)
-- `remote_grain_grpc.go` (adapter bridging existing interfaces)
-- `control_plane_adapter.go` (replaces frame handlers in `SyncedPool`)
-
-Modified:
-- `synced-pool.go` (remote host management now uses gRPC clients; negotiation logic updated)
-- `main.go` (initialize both gRPC services on startup)
-- `go.mod` (add `google.golang.org/grpc`)
-
----
-
-## 9. Step-by-Step Migration Plan
-
-1. Add proto files and generate Go code (`protoc --go_out --go-grpc_out`).
-2. Implement `CartActorServer`:
-   - Translate `MutationRequest` to `Message`.
-   - Use existing handler registry for payload encode/decode.
-   - Return JSON cart state.
-3. Implement `CartActorClient` wrapper (`RemoteGrainGRPC`) implementing:
-   - `HandleMessage`: Build envelope, call `Mutate`.
-   - `GetCurrentState`: Call `GetState`.
-4. Implement `ControlPlaneServer` with methods:
-   - `Ping`: returns host + time.
-   - `Negotiate`: merge host lists; emulate old logic.
-   - `GetCartIds`: iterate local grains.
-   - `ConfirmOwner`: replicate quorum flow (accept always; error path for future).
-   - `Closing`: schedule remote removal.
-5. Implement `ControlPlaneClient` used inside `SyncedPool.AddRemote`.
-6. Refactor `SyncedPool`:
-   - Replace frame handlers registration with gRPC client calls.
-   - Replace `Server.AddHandler(...)` start-up with launching gRPC server.
-   - Implement periodic health checks using `Ping`.
-7. Remove old connection constructs for 1337/1338.
-8. Metrics:
-   - Add unary interceptor capturing duration and status.
-   - Replace packet counters with `cart_grpc_mutate_calls_total`, `cart_grpc_control_calls_total`, histograms for latency.
-9. Update `main.go` to start:
-   - gRPC server(s).
-   - HTTP server as before.
-10. Delete legacy files & update README build instructions.
-11. Load testing & profiling on Raspberry Pi hardware (or ARM emulation).
-12. Final cleanup & dead code removal (search for now-unused constants & structs).
-13. Tag release.
-
----
-
-## 10. Performance Considerations (Raspberry Pi Focus)
-
-- Single `*grpc.ClientConn` per remote host (HTTP/2 multiplexing) to reduce file descriptor and handshake overhead.
-- Use small keepalive pings (optional) only if connections drop; default may suffice.
-- Avoid reflection / dynamic dispatch in hot path: pre-build a mapping from `MutationType` to handler function.
-- Reuse byte buffers:
-  - Implement a `sync.Pool` for mutation serialization to reduce GC pressure.
-- Enforce per-RPC deadlines (e.g. 300–400ms) to avoid pile-ups.
-- Backpressure:
-  - Before dispatch: if local grain pool at capacity and target grain is remote, abort early with 503 to caller (optional).
-- Disable gRPC compression for small payloads (mutation messages are small). Condition compression if payload > threshold (e.g. 8KB).
-- Compile with `-ldflags="-s -w"` in production to reduce binary size (optional).
-- Enable `GOMAXPROCS` tuned to CPU cores; Pi often benefits from leaving default but monitor.
-- Use histograms with limited buckets to reduce Prometheus cardinality.
-
----
-
-## 11. Testing Strategy
-
-Unit:
-- Message type mapping tests (legacy -> enum).
-- Envelope roundtrip: Original proto -> payload -> gRPC -> server decode -> internal Message.
-
-Integration:
-- Two-node cluster simulation:
-  - Mutate cart on Node A, ownership moves, verify remote access from Node B.
-  - Quorum failure simulation (temporarily reject `ConfirmOwner`).
-- Control plane negotiation: start nodes in staggered order, assert final membership.
-
-Load/Perf:
-- Benchmark local mutation vs remote mutation latency.
-- High concurrency test (N goroutines each performing X mutations).
-- Memory profiling (ensure no large buffer retention).
-
-Failure Injection:
-- Kill a node mid-mutation; client call should timeout and not corrupt local state.
-- Simulated network partition: drop `Ping` replies; ensure host removal path triggers.
-
----
-
-## 12. Rollback Strategy
-
-Because no mixed-version compatibility is provided, rollback = redeploy previous version containing legacy protocol:
-1. Stop all new-version pods.
-2. Deploy old version cluster-wide.
-3. No data migration needed (event persistence unaffected).
-
-Note: Avoid partial upgrades; perform full rolling restart quickly to prevent split-brain (new nodes won’t talk to old nodes).
-
----
-
-## 13. Risks & Mitigations
-
-| Risk | Description | Mitigation |
-|------|-------------|------------|
-| Full-cluster restart required | No mixed compatibility | Schedule maintenance window |
-| gRPC adds CPU overhead | Envelope + marshaling cost | Buffer reuse, keep small messages uncompressed |
-| Ownership race | Timing differences after refactor | Add explicit logs + tests around `RequestOwnership` path |
-| Hidden dependency on frame-level status codes | Some code may assume `FrameWithPayload` fields | Wrap gRPC responses into minimal compatibility structs until fully removed |
-| Memory growth | Connection reuse & pooled buffers not implemented initially | Add `sync.Pool` & track memory via pprof early |
-
----
-
-## 14. Logging & Observability
-
-- Structured log entries for:
-  - Ownership changes
-  - Negotiation rounds
-  - Remote spawn events
-  - Mutation failures (with cart id, mutation type)
-- Metrics:
-  - `cart_grpc_mutate_duration_seconds` (histogram)
-  - `cart_grpc_mutate_errors_total`
-  - `cart_grpc_control_duration_seconds`
-  - `cart_remote_hosts` (gauge)
-  - Retain existing grain counts.
-- Optional future: OpenTelemetry tracing (span per remote mutation).
-
----
-
-## 15. Future Enhancements (Post-Migration)
-
-- Replace JSON state with `CartState` proto and provide streaming watch API.
-- mTLS between nodes (certificate rotation via K8s Secret or SPIRE).
-- Distributed tracing integration.
-- Ownership leasing with TTL and optimistic renewal.
-- Delta replication or CRDT-based conflict resolution for experimentation.
-
----
-
-## 16. Task Breakdown & Estimates
-
-| Task | Estimate |
-|------|----------|
-| Proto definitions & generation | 0.5d |
-| CartActor server/client | 1.0d |
-| ControlPlane server/client | 1.0d |
-| SyncedPool refactor | 1.0d |
-| Metrics & interceptors | 0.5d |
-| Remove legacy code & cleanup | 0.5d |
-| Tests (unit + integration) | 1.5d |
-| Benchmark & tuning | 0.5–1.0d |
-| Total | ~6–7d |
-
----
-
-## 17. Open Questions (Confirm Before Implementation)
-
-1. Combine both services on a single port (simplify ops) or keep dual-port first? (Default here: keep dual, but easy to merge.)
-2. Minimum Go version remains 1.24.x—acceptable to add `google.golang.org/grpc` latest?
-3. Accept adding `sync.Pool` micro-optimizations in first pass or postpone?
-
----
-
-## 18. Acceptance Criteria
-
-- All previous integration tests (adjusted to gRPC) pass.
-- Cart operations (add, remove, delivery, checkout) function across at least a 2‑node cluster.
-- Control plane negotiation forms consistent host list.
-- Latency for a remote mutation does not degrade beyond an acceptable threshold (define baseline before merge).
-- Legacy networking code fully removed.
-
----
-
-## 19. Next Steps (If Approved)
-
-1. Implement proto files and commit.
-2. Scaffold server & client code.
-3. Refactor `SyncedPool` and `main.go`.
-4. Add metrics and tests.
-5. Run benchmark on target Pi hardware.
-6. Review & merge.
-
----
-
-End of Plan.

Makefile

@@ -0,0 +1,132 @@
+# ------------------------------------------------------------------------------
+# Makefile for go-cart-actor
+#
+# Key targets:
+#   make protogen      - Generate protobuf + gRPC code into proto/
+#   make clean_proto   - Remove generated proto *.pb.go files
+#   make verify_proto  - Ensure no stray root-level *.pb.go files exist
+#   make build         - Build the project
+#   make test          - Run tests (verbose)
+#   make tidy          - Run go mod tidy
+#   make regen         - Clean proto, regenerate, tidy, verify, build
+#   make help          - Show this help
+#
+# Conventions:
+#   - All .proto files live in $(PROTO_DIR)
+#   - Generated Go code is emitted under $(PROTO_DIR) via go_package mapping
+#   - go_package is set to: git.tornberg.me/go-cart-actor/proto;messages
+# ------------------------------------------------------------------------------
+
+MODULE_PATH := git.tornberg.me/go-cart-actor
+PROTO_DIR   := proto
+PROTOS      := $(PROTO_DIR)/messages.proto $(PROTO_DIR)/control_plane.proto
+
+# Allow override: make PROTOC=/path/to/protoc
+PROTOC ?= protoc
+
+# Tools (auto-detect; can override)
+PROTOC_GEN_GO        ?= $(shell command -v protoc-gen-go 2>/dev/null)
+PROTOC_GEN_GO_GRPC   ?= $(shell command -v protoc-gen-go-grpc 2>/dev/null)
+
+GO        ?= go
+
+# Colors (optional)
+GREEN  := \033[32m
+RED    := \033[31m
+YELLOW := \033[33m
+RESET  := \033[0m
+
+# ------------------------------------------------------------------------------
+
+.PHONY: protogen clean_proto verify_proto tidy build test regen help check_tools
+
+help:
+	@echo "Available targets:"
+	@echo "  protogen      Generate protobuf & gRPC code"
+	@echo "  clean_proto   Remove generated *.pb.go files in $(PROTO_DIR)"
+	@echo "  verify_proto  Ensure no root-level *.pb.go files (old layout)"
+
+	@echo "  tidy          Run go mod tidy"
+	@echo "  build         Build the module"
+	@echo "  test          Run tests (verbose)"
+	@echo "  regen         Clean proto, regenerate, tidy, verify, and build"
+	@echo "  check_tools   Verify protoc + plugins are installed"
+
+check_tools:
+	@if [ -z "$(PROTOC_GEN_GO)" ] || [ -z "$(PROTOC_GEN_GO_GRPC)" ]; then \
+		echo "$(RED)Missing protoc-gen-go or protoc-gen-go-grpc in PATH.$(RESET)"; \
+		echo "Install with:"; \
+		echo "  go install google.golang.org/protobuf/cmd/protoc-gen-go@latest"; \
+		echo "  go install google.golang.org/grpc/cmd/protoc-gen-go-grpc@latest"; \
+		exit 1; \
+	fi
+	@if ! command -v "$(PROTOC)" >/dev/null 2>&1; then \
+		echo "$(RED)protoc not found. Install protoc (e.g. via package manager)$(RESET)"; \
+		exit 1; \
+	fi
+	@echo "$(GREEN)All required tools detected.$(RESET)"
+
+protogen: check_tools
+	@echo "$(YELLOW)Generating protobuf code (outputs -> ./proto)...$(RESET)"
+	$(PROTOC) -I $(PROTO_DIR) \
+	  --go_out=./proto --go_opt=paths=source_relative \
+	  --go-grpc_out=./proto --go-grpc_opt=paths=source_relative \
+	  $(PROTOS)
+	@echo "$(GREEN)Protobuf generation complete.$(RESET)"
+
+clean_proto:
+	@echo "$(YELLOW)Removing generated protobuf files...$(RESET)"
+	@rm -f $(PROTO_DIR)/*_grpc.pb.go $(PROTO_DIR)/*.pb.go
+	@rm -f *.pb.go
+	@rm -rf git.tornberg.me
+	@echo "$(GREEN)Clean complete.$(RESET)"
+
+verify_proto:
+	@echo "$(YELLOW)Verifying proto layout...$(RESET)"
+	@if ls *.pb.go >/dev/null 2>&1; then \
+		echo "$(RED)ERROR: Found root-level generated *.pb.go files (should be only under $(PROTO_DIR)/).$(RESET)"; \
+		ls -1 *.pb.go; \
+		exit 1; \
+	fi
+	@echo "$(GREEN)Proto layout OK (no root-level *.pb.go files).$(RESET)"
+
+
+
+
+
+
+
+
+
+
+
+
+
+tidy:
+	@echo "$(YELLOW)Running go mod tidy...$(RESET)"
+	$(GO) mod tidy
+	@echo "$(GREEN)tidy complete.$(RESET)"
+
+build:
+	@echo "$(YELLOW)Building...$(RESET)"
+	$(GO) build ./...
+	@echo "$(GREEN)Build success.$(RESET)"
+
+test:
+	@echo "$(YELLOW)Running tests...$(RESET)"
+	$(GO) test -v ./...
+	@echo "$(GREEN)Tests completed.$(RESET)"
+
+regen: clean_proto protogen tidy verify_proto build
+	@echo "$(GREEN)Full regenerate cycle complete.$(RESET)"
+
+# Utility: show proto sources and generated outputs
+print_proto:
+	@echo "Proto sources:"
+	@ls -1 $(PROTOS)
+	@echo ""
+	@echo "Generated files (if any):"
+	@ls -1 $(PROTO_DIR)/*pb.go 2>/dev/null || echo "(none)"
+
+# Prevent make from treating these as file targets if similarly named files appear.
+.SILENT: help check_tools protogen clean_proto verify_proto tidy build test regen print_proto

README.md

@@ -1,5 +1,36 @@
 # Go Cart Actor
 
+## Migration Notes (Ring-based Ownership Transition)
+
+This release removes the legacy ConfirmOwner ownership negotiation RPC in favor of deterministic ownership via the consistent hashing ring.
+
+Summary of changes:
+- ConfirmOwner RPC removed from the ControlPlane service.
+- OwnerChangeRequest message removed (was only used by ConfirmOwner).
+- OwnerChangeAck retained solely as the response type for the Closing RPC.
+- SyncedPool now relies exclusively on the ring for ownership (no quorum negotiation).
+- Remote proxy creation includes a bounded readiness retry to reduce first-call failures.
+- New Prometheus ring metrics: 
+  - cart_ring_epoch
+  - cart_ring_hosts
+  - cart_ring_vnodes
+  - cart_ring_host_share{host}
+  - cart_ring_lookup_local_total
+  - cart_ring_lookup_remote_total
+
+Action required for consumers:
+1. Regenerate protobuf code after pulling (requires protoc-gen-go and protoc-gen-go-grpc installed).
+2. Remove any client code or automation invoking ConfirmOwner (calls will now return UNIMPLEMENTED if using stale generated stubs).
+3. Update monitoring/alerts that referenced ConfirmOwner or ownership quorum failures—use ring metrics instead.
+4. If you previously interpreted “ownership flapping” via ConfirmOwner logs, now check for:
+   - Rapid changes in ring epoch (cart_ring_epoch)
+   - Host churn (cart_ring_hosts)
+   - Imbalance in vnode distribution (cart_ring_host_share)
+
+No data migration is necessary; cart IDs and grain state are unaffected.
+
+---
+
 A distributed cart management system using the actor model pattern.
 
 ## Prerequisites
@@ -175,4 +206,239 @@ curl --cookie cookies.txt http://localhost:8080/cart/add/TEST-SKU-123
 
 - Always regenerate protobuf Go code after modifying any `.proto` files (messages/cart_actor/control_plane)
 - The generated `messages.pb.go` file should not be edited manually
-- Make sure your PATH includes the protoc-gen-go binary location (usually `$GOPATH/bin`)
+- Make sure your PATH includes the protoc-gen-go binary location (usually `$GOPATH/bin`)
+
+---
+
+## Architecture Overview
+
+The system is a distributed, sharded (by cart id) actor model implementation:
+
+- Each cart is a grain (an in‑memory struct `*CartGrain`) that owns and mutates its own state.
+- A **local grain pool** holds grains owned by the node.
+- A **synced (cluster) pool** (`SyncedPool`) coordinates multiple nodes and exposes local or remote grains through a uniform interface (`GrainPool`).
+- All inter‑node communication is gRPC:
+  - Cart mutation & state RPCs (CartActor service).
+  - Control plane RPCs (ControlPlane service) for membership, ownership negotiation, liveness, and graceful shutdown.
+
+### Key Processes
+
+1. Client HTTP request (or gRPC client) arrives with a cart identifier (cookie or path).
+2. The pool resolves ownership:
+   - If local grain exists → use it.
+   - If a remote host is known owner → a remote grain proxy (`RemoteGrainGRPC`) is used; it performs gRPC calls to the owning node.
+   - If ownership is unknown → node attempts to claim ownership (quorum negotiation) and spawns a local grain.
+3. Mutation is executed via the **mutation registry** (registry wraps domain logic + optional totals recomputation).
+4. Updated state returned to caller; ownership preserved unless relinquished later (not yet implemented to shed load).
+
+---
+
+## Grain & Mutation Model
+
+- `CartGrain` holds items, deliveries, pricing aggregates, and checkout/order metadata.
+- All mutations are registered via `RegisterMutation[T]` with signature:
+  ```
+  func(*CartGrain, *T) error
+  ```
+- `WithTotals()` flag triggers automatic recalculation of totals after successful handlers.
+- The old giant `switch` in `CartGrain.Apply` has been replaced by registry dispatch; unregistered mutations fail fast.
+- Adding a mutation:
+  1. Define proto message.
+  2. Generate code.
+  3. Register handler (optionally WithTotals).
+  4. Add gRPC RPC + request wrapper if the mutation must be remotely invokable.
+  5. (Optional) Add HTTP endpoint mapping to the mutation.
+
+---
+
+## Local Grain Pool
+
+- Manages an in‑memory map `map[CartId]*CartGrain`.
+- Lazy spawn: first mutation or explicit access triggers `spawn(id)`.
+- TTL / purge loop periodically removes expired grains unless they changed recently (basic memory pressure management).
+- Capacity limit (`PoolSize`); oldest expired grain evicted first when full.
+
+---
+
+## Synced (Cluster) Pool
+
+`SyncedPool` wraps a local pool and tracks:
+
+- `remoteHosts`: known peer nodes (gRPC connections).
+- `remoteIndex`: mapping of cart id → remote grain proxy (`RemoteGrainGRPC`) for carts owned elsewhere.
+
+Responsibilities:
+
+1. Discovery integration (via a `Discovery` interface) adds/removes hosts.
+2. Periodic ping health checks (ControlPlane.Ping).
+3. Ring-based deterministic ownership:
+   - Ownership is derived directly from the consistent hashing ring (no quorum RPC or `ConfirmOwner`).
+4. Remote spawning:
+   - When a remote host reports its cart ids (`GetCartIds`), the pool creates remote proxies for fast routing.
+
+---
+
+## Remote Grain Proxies
+
+A `RemoteGrainGRPC` implements the `Grain` interface but delegates:
+
+- `Apply` → Specific CartActor per‑mutation RPC (e.g., `AddItem`, `RemoveItem`) constructed from the mutation type. (Legacy envelope removed.)
+- `GetCurrentState` → `CartActor.GetState`.
+
+Return path:
+
+1. gRPC reply (CartMutationReply / StateReply) → proto `CartState`.
+2. `ToCartState` / mapping reconstructs a local `CartGrain` snapshot for callers expecting grain semantics.
+
+---
+
+## Control Plane (Inter‑Node Coordination)
+
+Defined in `proto/control_plane.proto`:
+
+| RPC | Purpose |
+|-----|---------|
+| `Ping` | Liveness; increments missed ping counter if failing. |
+| `Negotiate` | Merges membership views; used after discovery events. |
+| `GetCartIds` | Enumerate locally owned carts for remote index seeding. |
+| `Closing` | Graceful shutdown notice; peers remove host & associated remote grains. |
+
+### Ownership / Quorum Rules
+
+- If total participating hosts < 3 → all must accept.
+- Otherwise majority acceptance (`ok >= total/2`).
+- On failure → local tentative grain is removed (rollback to avoid split‑brain).
+
+---
+
+## Request / Mutation Flow Examples
+
+### Local Mutation
+1. HTTP handler parses request → determines cart id.
+2. `SyncedPool.Apply`:
+   - Finds local grain (or spawns new after quorum).
+   - Executes registry mutation.
+3. Totals updated if flagged.
+4. HTTP response returns updated JSON (via `ToCartState`).
+
+### Remote Mutation
+1. `SyncedPool.Apply` sees cart mapped to a remote host.
+2. Routes to `RemoteGrainGRPC.Apply`.
+3. Remote node executes mutation locally and returns updated state over gRPC.
+4. Proxy materializes snapshot locally (not authoritative, read‑only view).
+
+### Checkout (Side‑Effecting, Non-Pure)
+- HTTP `/checkout` uses current grain snapshot to build payload (pure function).
+- Calls Klarna externally (not a mutation).
+- Applies `InitializeCheckout` mutation to persist reference + status.
+- Returns Klarna order JSON to client.
+
+---
+
+## Scaling & Deployment
+
+- **Horizontal scaling**: Add more nodes; discovery layer (Kubernetes / service registry) feeds hosts to `SyncedPool`.
+- **Sharding**: Implicit by cart id hash. Ownership is first-claim with quorum acceptance.
+- **Hot spots**: A single popular cart remains on one node; for heavy multi-client concurrency, future work could add read replicas or partitioning (not implemented).
+- **Capacity tuning**: Increase `PoolSize` & memory limits; adjust TTL for stale cart eviction.
+
+### Adding Nodes
+1. Node starts gRPC server (CartActor + ControlPlane).
+2. After brief delay, begins discovery watch; on event:
+   - New host → dial + negotiate → seed remote cart ids.
+3. Pings maintain health; failed hosts removed (proxies invalidated).
+
+---
+
+## Failure Handling
+
+| Scenario | Behavior |
+|----------|----------|
+| Remote host unreachable | Pings increment `MissedPings`; after threshold host removed. |
+| Ownership negotiation fails | Tentative local grain discarded. |
+| gRPC call error on remote mutation | Error bubbled to caller; no local fallback. |
+| Missing mutation registration | Fast failure with explicit error message. |
+| Partial checkout (Klarna fails) | No local state mutation for checkout; client sees error; cart remains unchanged. |
+
+---
+
+## Mutation Registry Summary
+
+- Central, type-safe registry prevents silent omission.
+- Each handler:
+  - Validates input.
+  - Mutates `*CartGrain`.
+  - Returns error for rejection.
+- Automatic totals recomputation reduces boilerplate and consistency risk.
+- Coverage test (add separately) can enforce all proto mutations are registered.
+
+---
+
+## gRPC Interfaces
+
+- **CartActor**: Per-mutation unary RPCs + `GetState`. (Checkout logic intentionally excluded; handled at HTTP layer.)
+- **ControlPlane**: Cluster coordination (Ping, Negotiate, GetCartIds, Closing) — ownership now ring-determined (no ConfirmOwner).
+
+**Ports** (default / implied):
+- CartActor & ControlPlane share the same gRPC server/listener (single port, e.g. `:1337`).
+- Legacy frame/TCP code has been removed.
+
+---
+
+## Security & Future Enhancements
+
+| Area | Potential Improvement |
+|------|------------------------|
+| Transport Security | Add TLS / mTLS to gRPC servers & clients. |
+| Auth / RBAC | Intercept CartActor RPCs with auth metadata. |
+| Backpressure | Rate-limit remote mutation calls per host. |
+| Observability | Add per-mutation Prometheus metrics & tracing spans. |
+| Ownership | Add lease timeouts / fencing tokens for stricter guarantees. |
+| Batch Ops | Introduce batch mutation RPC or streaming updates (WatchState). |
+| Persistence | Reintroduce event log or snapshot persistence layer if durability required. |
+
+---
+
+## Adding a New Node (Operational Checklist)
+
+1. Deploy binary/container with same proto + registry.
+2. Expose gRPC port.
+3. Ensure discovery lists the new host.
+4. Node dials peers, negotiates membership.
+5. Remote cart proxies seeded.
+6. Traffic routed automatically based on ownership.
+
+---
+
+## Adding a New Mutation (Checklist Recap)
+
+1. Define proto message (+ request wrapper & RPC if remote invocation needed).
+2. Regenerate protobuf code.
+3. Implement & register handler (`RegisterMutation`).
+4. Add client (HTTP/gRPC) endpoint.
+5. Write unit + integration tests.
+6. (Optional) Add to coverage test list and docs.
+
+---
+
+## High-Level Data Flow Diagram (Text)
+
+```
+Client -> HTTP Handler -> SyncedPool -> (local?) -> Registry -> Grain State
+                       \-> (remote?) -> RemoteGrainGRPC -> gRPC -> Remote CartActor -> Registry -> Grain
+ControlPlane: Discovery Events <-> Negotiation/Ping <-> SyncedPool state (ring determines ownership)
+```
+
+---
+
+## Troubleshooting
+
+| Symptom | Likely Cause | Action |
+|---------|--------------|--------|
+| New cart every request | Secure cookie over plain HTTP or not sending cookie jar | Disable Secure locally or use HTTPS & proper curl `-b` |
+| Unsupported mutation error | Missing registry handler | Add `RegisterMutation` for that proto |
+| Ownership imbalance | Ring host distribution skew or rapid host churn | Examine `cart_ring_host_share`, `cart_ring_hosts`, and logs for host add/remove; rebalance or investigate instability |
+| Remote mutation latency | Network / serialization overhead | Consider batching or colocating hot carts |
+| Checkout returns 500 | Klarna call failed | Inspect logs; no grain state mutated |
+
+---

TODO.md

@@ -0,0 +1,245 @@
+# TODO / Roadmap
+
+A living roadmap for improving the cart actor system. Focus areas:
+1. Reliability & correctness
+2. Simplicity of mutation & ownership flows
+3. Developer experience (DX)
+4. Operability (observability, tracing, metrics)
+5. Performance & scalability
+6. Security & multi-tenant readiness
+
+---
+
+## 1. Immediate Next Steps (High-Leverage)
+
+| Priority | Task | Goal | Effort | Owner | Notes |
+|----------|------|------|--------|-------|-------|
+| P0 | Add mutation registry coverage test | Ensure no unregistered mutations silently fail | S |  | Failing fast in CI |
+| P0 | Add decodeJSON helper + 400 mapping for EOF | Reduce noisy 500 logs | S |  | Improves client API clarity |
+| P0 | Regenerate protos & prune unused messages (CreateCheckoutOrder, Checkout RPC remnants) | Eliminate dead types | S |  | Avoid confusion |
+| P0 | Add integration test: multi-node ownership negotiation | Validate quorum logic | M |  | Spin up 2–3 nodes ephemeral |
+| P1 | Export Prometheus metrics for per-mutation counts & latency | Operability | M |  | Wrap registry handlers |
+| P1 | Add graceful shutdown ordering (Closing → wait for acks → stop gRPC) | Reduce in-flight mutation failures | S |  | Add context cancellation |
+| P1 | Add coverage for InitializeCheckout / OrderCreated flows | Checkout reliability | S |  | Simulate Klarna stub |
+| P2 | Add optional batching client (apply multiple mutations locally then persist) | Performance | M |  | Only if needed |
+
+---
+
+## 2. Simplification Opportunities
+
+### A. RemoteGrain Proxy Mapping
+Current: manual switch building each RPC call.
+Simplify by:
+- Generating a thin client adapter from proto RPC descriptors (codegen).
+- Or using a registry similar to mutation registry but for “outbound call constructors”.
+Benefit: adding a new mutation = add proto + register server handler + register outbound invoker (no switch edits).
+
+### B. Ownership Negotiation
+Current: ad hoc quorum rule in `SyncedPool`.
+Simplify:
+- Introduce explicit `OwnershipLease{holder, expiresAt, version}`.
+- Use monotonic version increment—reject stale ConfirmOwner replies.
+- Optional: add randomized backoff to reduce thundering herd on contested cart ids.
+
+### C. CartId Handling
+Current: ephemeral 16-byte array with trimmed string semantics.
+Simplify:
+- Use ULID / UUIDv7 (time-ordered, collision-resistant) for easier external correlation.
+- Provide helper `NewCartIdString()` and keep internal fixed-size if still desired.
+
+### D. Mutation Signatures
+Current: registry assumes `func(*CartGrain, *T) error`.
+Extension option: allow pure transforms returning a delta struct (for audit/logging):
+```
+type MutationResult struct {
+  Changed bool
+  Events  []interface{}
+}
+```
+Only implement if auditing/event-sourcing reintroduced.
+
+---
+
+## 3. Developer Experience Improvements
+
+| Task | Rationale | Approach |
+|------|-----------|----------|
+| Makefile targets: `make run-single`, `make run-multi N=3` | Faster local cluster spin-up | Docker compose or background “mini cluster” scripts |
+| Template for new mutation (generator) | Reduce boilerplate | `go:generate` scanning proto for new RPCs |
+| Lint config (golangci-lint) | Catch subtle issues early | Add `.golangci.yml` |
+| Pre-commit hook for proto regeneration check | Avoid stale generated code | Script compares git diff after `make protogen` |
+| Example client (Go + curl snippets auto-generated) | Onboarding | Codegen a markdown from proto comments |
+
+---
+
+## 4. Observability / Metrics / Tracing
+
+| Area | Metric / Trace | Notes |
+|------|----------------|-------|
+| Mutation registry | `cart_mutations_total{type,success}`; duration histogram | Wrap handler |
+| Ownership negotiation | `cart_ownership_attempts_total{result}` | result=accepted,rejected,timeout |
+| Remote latency | `cart_remote_mutation_seconds{method}` | Use client interceptors |
+| Pings | `cart_remote_missed_pings_total{host}` | Already count, expose |
+| Checkout flow | `checkout_attempts_total`, `checkout_failures_total` | Differentiate Klarna vs internal errors |
+| Tracing | Span: HTTP handler → SyncedPool.Apply → (Remote?) gRPC → mutation handler | Add OpenTelemetry instrumentation |
+
+---
+
+## 5. Performance & Scalability
+
+| Concern | Idea | Trade-Off |
+|---------|------|-----------|
+| High mutation rate on single cart | Introduce optional mutation queue (serialize explicitly) | Slight latency increase per op |
+| Remote call overhead | Add client-side gRPC pooling & per-host circuit breaker | Complexity vs resilience |
+| TTL purge efficiency | Use min-heap or timing wheel instead of slice scan | More code, better big-N performance |
+| Batch network latency | Add `BatchMutate` RPC (list of mutations applied atomically) | Lost single-op simplicity |
+
+---
+
+## 6. Reliability Features
+
+| Feature | Description | Priority |
+|---------|-------------|----------|
+| Lease fencing token | Include `ownership_version` in all remote mutate requests | M |
+| Retry policy | Limited retry for transient network errors (idempotent mutations only) | L |
+| Dead host reconciliation | On host removal, proactively attempt re-acquire of its carts | M |
+| Drain mode | Node marks itself “draining” → refuses new ownership claims | M |
+
+---
+
+## 7. Security & Hardening
+
+| Area | Next Step | Detail |
+|------|-----------|--------|
+| Transport | mTLS on gRPC | Use SPIFFE IDs or simple CA |
+| AuthN/AuthZ | Interceptor enforcing service token | Inject metadata header |
+| Input validation | Strengthen JSON decode responses | Disallow unknown fields globally |
+| Rate limiting | Per-IP / per-cart throttling | Guard hotspot abuse |
+| Multi-tenancy | Tenant id dimension in cart id or metadata | Partition metrics & ownership |
+
+---
+
+## 8. Testing Strategy Enhancements
+
+| Gap | Improvement |
+|-----|------------|
+| No multi-node integration test in CI | Spin ephemeral in-process servers on randomized ports |
+| Mutation regression | Table-driven tests auto-discover handlers via registry |
+| Ownership race | Stress test: concurrent Apply on same new cart id from N goroutines |
+| Checkout external dependency | Klarna mock server (HTTptest) + deterministic responses |
+| Fuzzing | Fuzz `BuildCheckoutOrderPayload` & mutation handlers for panics |
+
+---
+
+## 9. Cleanup / Tech Debt
+
+| Item | Action |
+|------|--------|
+| Remove deprecated proto remnants (CreateCheckoutOrder, Checkout RPC) | Delete & regenerate |
+| Consolidate duplicate tax computations | Single helper with tax config |
+| Delivery price hard-coded (4900) | Config or pricing strategy interface |
+| Mixed naming (camel vs snake JSON historically) | Provide stable external API doc; accept old forms if needed |
+| Manual remote mutation switch (if still present) | Replace with generated outbound registry |
+| Mixed error responses (string bodies) | Standardize JSON: `{ "error": "...", "code": 400 }` |
+
+---
+
+## 10. Potential Future Features
+
+| Feature | Value | Complexity |
+|---------|-------|------------|
+| Streaming `WatchState` RPC | Real-time cart updates for clients | Medium |
+| Event sourcing / audit log | Replay, analytics, debugging | High |
+| Promotion / coupon engine plugin | Business extensibility | Medium |
+| Partial cart reservation / inventory lock | Stock accuracy under concurrency | High |
+| Multi-currency pricing | Globalization | Medium |
+| GraphQL facade | Client flexibility | Medium |
+
+---
+
+## 11. Suggested Prioritized Backlog (Condensed)
+
+1. Coverage test + decode error mapping (P0)
+2. Proto regeneration & cleanup (P0)
+3. Metrics wrapper for registry (P1)
+4. Multi-node ownership integration test (P1)
+5. Delivery pricing abstraction (P2)
+6. Lease version in remote RPCs (P2)
+7. BatchMutate evaluation (P3)
+8. TLS / auth hardening (P3) if going multi-tenant/public
+9. Event sourcing (Evaluate after stability) (P4)
+
+---
+
+## 12. Simplifying the Developer Workflow
+
+| Pain | Simplifier |
+|------|------------|
+| Manual mutation boilerplate | Code generator for registry stubs |
+| Forgetting totals | Enforce WithTotals lint: fail if mutation touches items/deliveries without flag |
+| Hard to inspect remote ownership | `/internal/ownership` debug endpoint (JSON of local + remoteIndex) |
+| Hard to see mutation timings | Add `?debug=latency` header to return per-mutation durations |
+| Cookie dev confusion (Secure flag) | Env var: `DEV_INSECURE_COOKIES=1` |
+
+---
+
+## 13. Example: Mutation Codegen Sketch (Future)
+
+Input: cart_actor.proto  
+Output: `mutation_auto.go`
+- Detect messages used in RPC wrappers (e.g., `AddItemRequest` → payload field).
+- Generate `RegisterMutation` template if handler not found.
+- Mark with `// TODO implement logic`.
+
+---
+
+## 14. Risk / Impact Matrix (Abbreviated)
+
+| Change | Risk | Mitigation |
+|--------|------|-----------|
+| Replace remote switch with registry | Possible missing registration → runtime error | Coverage test gating CI |
+| Lease introduction | Split-brain if version mishandled | Increment + assert monotonic; test race |
+| BatchMutate | Large atomic operations starving others | Size limits & fair scheduling |
+| Event sourcing | Storage + replay complexity | Start with append-only log + compaction job |
+
+---
+
+## 15. Contributing Workflow (Proposed)
+
+1. Add / modify proto → run `make protogen`
+2. Implement mutation logic → add `RegisterMutation` invocation
+3. Add/Update tests (unit + integration)
+4. Run `make verify` (lint, test, coverage, proto diff)
+5. Open PR (template auto-checklist referencing this TODO)
+6. Merge requires green CI + coverage threshold
+
+---
+
+## 16. Open Questions
+
+| Question | Notes |
+|----------|-------|
+| Do we need sticky sessions for HTTP layer scaling? | Currently cart id routing suffices |
+| Should deliveries prune invalid line references on SetCartRequest? | Inconsistency risk; add optional cleanup |
+| Is checkout idempotency strict enough? | Multiple create vs update semantics |
+| Add version field to CartState for optimistic concurrency? | Could enable external CAS writes |
+
+---
+
+## 17. Tracking
+
+Mark any completed tasks with `[x]`:
+
+- [ ] Coverage test
+- [ ] Decode helper + 400 mapping
+- [ ] Proto cleanup
+- [ ] Registry metrics instrumentation
+- [ ] Ownership multi-node test
+- [ ] Lease versioning
+- [ ] Delivery pricing abstraction
+- [ ] TLS/mTLS internal
+- [ ] BatchMutate design doc
+
+---
+
+_Last updated: roadmap draft – refine after first metrics & scaling test run._

amqp-order-handler.go

@@ -1,83 +1,61 @@
 package main
 
 import (
-	"log"
+	"context"
+	"fmt"
+	"time"
 
 	amqp "github.com/rabbitmq/amqp091-go"
 )
 
 type AmqpOrderHandler struct {
 	Url        string
-	connection *amqp.Connection
-	//channel    *amqp.Channel
+	Connection *amqp.Connection
+	Channel    *amqp.Channel
 }
 
-const (
-	topic = "order-placed"
-)
-
-func (t *AmqpOrderHandler) Connect() error {
-
-	conn, err := amqp.DialConfig(t.Url, amqp.Config{
-		//Vhost:      "/",
-		Properties: amqp.NewConnectionProperties(),
-	})
-
+func (h *AmqpOrderHandler) Connect() error {
+	conn, err := amqp.Dial(h.Url)
 	if err != nil {
-		return err
+		return fmt.Errorf("failed to connect to RabbitMQ: %w", err)
 	}
-	t.connection = conn
+	h.Connection = conn
+
 	ch, err := conn.Channel()
 	if err != nil {
-		return err
-	}
-	defer ch.Close()
-	if err := ch.ExchangeDeclare(
-		topic,   // name
-		"topic", // type
-		true,    // durable
-		false,   // auto-delete
-		false,   // internal
-		false,   // noWait
-		nil,     // arguments
-	); err != nil {
-		return err
-	}
-
-	if _, err = ch.QueueDeclare(
-		topic, // name of the queue
-		true,  // durable
-		false, // delete when unused
-		false, // exclusive
-		false, // noWait
-		nil,   // arguments
-	); err != nil {
-		return err
+		return fmt.Errorf("failed to open a channel: %w", err)
 	}
+	h.Channel = ch
 
 	return nil
 }
 
-func (t *AmqpOrderHandler) Close() error {
-	log.Println("Closing master channel")
-	return t.connection.Close()
-	//return t.channel.Close()
+func (h *AmqpOrderHandler) Close() error {
+	if h.Channel != nil {
+		h.Channel.Close()
+	}
+	if h.Connection != nil {
+		return h.Connection.Close()
+	}
+	return nil
 }
 
-func (t *AmqpOrderHandler) OrderCompleted(data []byte) error {
-	ch, err := t.connection.Channel()
-	if err != nil {
-		return err
-	}
-	defer ch.Close()
-	return ch.Publish(
-		topic,
-		topic,
-		true,
-		false,
+func (h *AmqpOrderHandler) OrderCompleted(body []byte) error {
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	defer cancel()
+
+	err := h.Channel.PublishWithContext(ctx,
+		"orders", // exchange
+		"new",    // routing key
+		false,    // mandatory
+		false,    // immediate
 		amqp.Publishing{
 			ContentType: "application/json",
-			Body:        data,
-		},
-	)
+			Body:        body,
+		})
+	if err != nil {
+		return fmt.Errorf("failed to publish a message: %w", err)
+	}
+
+	return nil
 }

cart-grain.go

@@ -1,48 +1,16 @@
 package main
 
 import (
-	"bytes"
 	"encoding/json"
 	"fmt"
-	"log"
-	"slices"
 	"sync"
 	"time"
 
 	messages "git.tornberg.me/go-cart-actor/proto"
 )
 
-type CartId [16]byte
-
-// String returns the cart id as a trimmed UTF-8 string (trailing zero bytes removed).
-func (id CartId) String() string {
-	n := 0
-	for n < len(id) && id[n] != 0 {
-		n++
-	}
-	return string(id[:n])
-}
-
-// ToCartId converts an arbitrary string to a fixed-size CartId (truncating or padding with zeros).
-func ToCartId(s string) CartId {
-	var id CartId
-	copy(id[:], []byte(s))
-	return id
-}
-
-func (id CartId) MarshalJSON() ([]byte, error) {
-	return json.Marshal(id.String())
-}
-
-func (id *CartId) UnmarshalJSON(data []byte) error {
-	var str string
-	err := json.Unmarshal(data, &str)
-	if err != nil {
-		return err
-	}
-	copy(id[:], []byte(str))
-	return nil
-}
+// Legacy padded [16]byte CartId and its helper methods removed.
+// Unified CartId (uint64 with base62 string form) now defined in cart_id.go.
 
 type StockStatus int
 
@@ -93,7 +61,7 @@ type CartGrain struct {
 	mu                sync.RWMutex
 	lastItemId        int
 	lastDeliveryId    int
-	storageMessages   []Message
+	lastChange        int64           // unix seconds of last successful mutation (replay sets from event ts)
 	Id                CartId          `json:"id"`
 	Items             []*CartItem     `json:"items"`
 	TotalPrice        int64           `json:"totalPrice"`
@@ -108,8 +76,8 @@ type CartGrain struct {
 
 type Grain interface {
 	GetId() CartId
-	HandleMessage(message *Message, isReplay bool) (*FrameWithPayload, error)
-	GetCurrentState() (*FrameWithPayload, error)
+	Apply(content interface{}, isReplay bool) (*CartGrain, error)
+	GetCurrentState() (*CartGrain, error)
 }
 
 func (c *CartGrain) GetId() CartId {
@@ -117,20 +85,11 @@ func (c *CartGrain) GetId() CartId {
 }
 
 func (c *CartGrain) GetLastChange() int64 {
-	if len(c.storageMessages) == 0 {
-		return 0
-	}
-	return *c.storageMessages[len(c.storageMessages)-1].TimeStamp
+	return c.lastChange
 }
 
-func (c *CartGrain) GetCurrentState() (*FrameWithPayload, error) {
-	result, err := json.Marshal(c)
-	if err != nil {
-		ret := MakeFrameWithPayload(0, 400, []byte(err.Error()))
-		return &ret, nil
-	}
-	ret := MakeFrameWithPayload(0, 200, result)
-	return &ret, nil
+func (c *CartGrain) GetCurrentState() (*CartGrain, error) {
+	return c, nil
 }
 
 func getInt(data float64, ok bool) (int, error) {
@@ -201,30 +160,23 @@ func getItemData(sku string, qty int, country string) (*messages.AddItem, error)
 	}, nil
 }
 
-func (c *CartGrain) AddItem(sku string, qty int, country string, storeId *string) (*FrameWithPayload, error) {
+func (c *CartGrain) AddItem(sku string, qty int, country string, storeId *string) (*CartGrain, error) {
 	cartItem, err := getItemData(sku, qty, country)
 	if err != nil {
 		return nil, err
 	}
 	cartItem.StoreId = storeId
-	return c.HandleMessage(&Message{
-		Type:    2,
-		Content: cartItem,
-	}, false)
+	return c.Apply(cartItem, false)
 }
 
-func (c *CartGrain) GetStorageMessage(since int64) []StorableMessage {
-	c.mu.RLock()
-	defer c.mu.RUnlock()
-	ret := make([]StorableMessage, 0)
+/*
+Legacy storage (event sourcing) removed in oneof refactor.
+Kept stub (commented) for potential future reintroduction using proto envelopes.
 
-	for _, message := range c.storageMessages {
-		if *message.TimeStamp > since {
-			ret = append(ret, message)
-		}
-	}
-	return ret
+func (c *CartGrain) GetStorageMessage(since int64) []interface{} {
+	return nil
 }
+*/
 
 func (c *CartGrain) GetState() ([]byte, error) {
 	return json.Marshal(c)
@@ -279,324 +231,24 @@ func GetTaxAmount(total int64, tax int) int64 {
 	return int64(float64(total) / float64((1 + taxD)))
 }
 
-func (c *CartGrain) HandleMessage(message *Message, isReplay bool) (*FrameWithPayload, error) {
-	if message.TimeStamp == nil {
-		now := time.Now().Unix()
-		message.TimeStamp = &now
-	}
+func (c *CartGrain) Apply(content interface{}, isReplay bool) (*CartGrain, error) {
 	grainMutations.Inc()
-	var err error
-	switch message.Type {
-	case SetCartItemsType:
-		msg, ok := message.Content.(*messages.SetCartRequest)
-		if !ok {
-			err = fmt.Errorf("expected SetCartItems")
-		} else {
 
-			c.mu.Lock()
-			c.Items = make([]*CartItem, 0, len(msg.Items))
-			c.mu.Unlock()
-			for _, item := range msg.Items {
-				c.AddItem(item.Sku, int(item.Quantity), item.Country, item.StoreId)
-			}
-
-		}
-	case AddRequestType:
-		msg, ok := message.Content.(*messages.AddRequest)
-		if !ok {
-			err = fmt.Errorf("expected AddRequest")
-		} else {
-
-			existingItem, found := c.FindItemWithSku(msg.Sku)
-			if found {
-				existingItem.Quantity += int(msg.Quantity)
-				c.UpdateTotals()
-			} else {
-				return c.AddItem(msg.Sku, int(msg.Quantity), msg.Country, msg.StoreId)
-			}
-
-		}
-	case AddItemType:
-		msg, ok := message.Content.(*messages.AddItem)
-		if !ok {
-			err = fmt.Errorf("expected AddItem")
-		} else {
-
-			if msg.Quantity < 1 {
-				return nil, fmt.Errorf("invalid quantity")
-			}
-			existingItem, found := c.FindItemWithSku(msg.Sku)
-			if found {
-				existingItem.Quantity += int(msg.Quantity)
-				c.UpdateTotals()
-			} else {
-				c.mu.Lock()
-				c.lastItemId++
-				tax := 2500
-				if msg.Tax > 0 {
-					tax = int(msg.Tax)
-				}
-
-				taxAmount := GetTaxAmount(msg.Price, tax)
-
-				c.Items = append(c.Items, &CartItem{
-					Id:          c.lastItemId,
-					ItemId:      int(msg.ItemId),
-					Quantity:    int(msg.Quantity),
-					Sku:         msg.Sku,
-					Name:        msg.Name,
-					Price:       msg.Price,
-					TotalPrice:  msg.Price * int64(msg.Quantity),
-					TotalTax:    int64(taxAmount * int64(msg.Quantity)),
-					Image:       msg.Image,
-					Stock:       StockStatus(msg.Stock),
-					Disclaimer:  msg.Disclaimer,
-					Brand:       msg.Brand,
-					Category:    msg.Category,
-					Category2:   msg.Category2,
-					Category3:   msg.Category3,
-					Category4:   msg.Category4,
-					Category5:   msg.Category5,
-					OrgPrice:    msg.OrgPrice,
-					ArticleType: msg.ArticleType,
-					Outlet:      msg.Outlet,
-					SellerId:    msg.SellerId,
-					SellerName:  msg.SellerName,
-					Tax:         int(taxAmount),
-					TaxRate:     tax,
-					StoreId:     msg.StoreId,
-				})
-				c.UpdateTotals()
-				c.mu.Unlock()
-			}
-
-		}
-	case ChangeQuantityType:
-		msg, ok := message.Content.(*messages.ChangeQuantity)
-		if !ok {
-			err = fmt.Errorf("expected ChangeQuantity")
-		} else {
-
-			for i, item := range c.Items {
-				if item.Id == int(msg.Id) {
-					if msg.Quantity <= 0 {
-						//c.TotalPrice -= item.Price * int64(item.Quantity)
-						c.Items = append(c.Items[:i], c.Items[i+1:]...)
-					} else {
-						//diff := int(msg.Quantity) - item.Quantity
-						item.Quantity = int(msg.Quantity)
-						//c.TotalPrice += item.Price * int64(diff)
-					}
-
-					break
-				}
-			}
-			c.UpdateTotals()
-
-		}
-	case RemoveItemType:
-		msg, ok := message.Content.(*messages.RemoveItem)
-		if !ok {
-			err = fmt.Errorf("expected RemoveItem")
-		} else {
-
-			items := make([]*CartItem, 0, len(c.Items))
-			for _, item := range c.Items {
-				if item.Id == int(msg.Id) {
-					//c.TotalPrice -= item.Price * int64(item.Quantity)
-				} else {
-					items = append(items, item)
-				}
-			}
-			c.Items = items
-			c.UpdateTotals()
-		}
-	case SetDeliveryType:
-		msg, ok := message.Content.(*messages.SetDelivery)
-		if !ok {
-			err = fmt.Errorf("expected SetDelivery")
-		} else {
-
-			c.lastDeliveryId++
-			items := make([]int, 0)
-			withDelivery := c.ItemsWithDelivery()
-			if len(msg.Items) == 0 {
-				items = append(items, c.ItemsWithoutDelivery()...)
-			} else {
-				for _, id := range msg.Items {
-					for _, item := range c.Items {
-						if item.Id == int(id) {
-							if slices.Contains(withDelivery, item.Id) {
-								return nil, fmt.Errorf("item already has delivery")
-							}
-							items = append(items, int(item.Id))
-							break
-						}
-					}
-				}
-			}
-			if len(items) > 0 {
-				c.Deliveries = append(c.Deliveries, &CartDelivery{
-					Id:          c.lastDeliveryId,
-					Provider:    msg.Provider,
-					PickupPoint: msg.PickupPoint,
-					Price:       4900,
-					Items:       items,
-				})
-
-				c.UpdateTotals()
-
-			}
-
-		}
-	case RemoveDeliveryType:
-		msg, ok := message.Content.(*messages.RemoveDelivery)
-		if !ok {
-			err = fmt.Errorf("expected RemoveDelivery")
-		} else {
-
-			deliveries := make([]*CartDelivery, 0, len(c.Deliveries))
-			for _, delivery := range c.Deliveries {
-				if delivery.Id == int(msg.Id) {
-					c.TotalPrice -= delivery.Price
-				} else {
-					deliveries = append(deliveries, delivery)
-				}
-			}
-			c.Deliveries = deliveries
-			c.UpdateTotals()
-		}
-	case SetPickupPointType:
-		msg, ok := message.Content.(*messages.SetPickupPoint)
-		if !ok {
-			err = fmt.Errorf("expected SetPickupPoint")
-		} else {
-
-			for _, delivery := range c.Deliveries {
-				if delivery.Id == int(msg.DeliveryId) {
-					delivery.PickupPoint = &messages.PickupPoint{
-						Id:      msg.Id,
-						Address: msg.Address,
-						City:    msg.City,
-						Zip:     msg.Zip,
-						Country: msg.Country,
-						Name:    msg.Name,
-					}
-					break
-				}
-			}
-
-		}
-	case CreateCheckoutOrderType:
-		msg, ok := message.Content.(*messages.CreateCheckoutOrder)
-		if !ok {
-			err = fmt.Errorf("expected CreateCheckoutOrder")
-		} else {
-
-			orderLines := make([]*Line, 0, len(c.Items))
-
-			c.PaymentInProgress = true
-			c.Processing = true
-			for _, item := range c.Items {
-
-				orderLines = append(orderLines, &Line{
-					Type:           "physical",
-					Reference:      item.Sku,
-					Name:           item.Name,
-					Quantity:       item.Quantity,
-					UnitPrice:      int(item.Price),
-					TaxRate:        2500, // item.TaxRate,
-					QuantityUnit:   "st",
-					TotalAmount:    int(item.TotalPrice),
-					TotalTaxAmount: int(item.TotalTax),
-					ImageURL:       fmt.Sprintf("https://www.elgiganten.se%s", item.Image),
-				})
-			}
-			for _, line := range c.Deliveries {
-				if line.Price > 0 {
-					orderLines = append(orderLines, &Line{
-						Type:           "shipping_fee",
-						Reference:      line.Provider,
-						Name:           "Delivery",
-						Quantity:       1,
-						UnitPrice:      int(line.Price),
-						TaxRate:        2500, // item.TaxRate,
-						QuantityUnit:   "st",
-						TotalAmount:    int(line.Price),
-						TotalTaxAmount: int(GetTaxAmount(line.Price, 2500)),
-					})
-				}
-			}
-			order := CheckoutOrder{
-				PurchaseCountry:    "SE",
-				PurchaseCurrency:   "SEK",
-				Locale:             "sv-se",
-				OrderAmount:        int(c.TotalPrice),
-				OrderTaxAmount:     int(c.TotalTax),
-				OrderLines:         orderLines,
-				MerchantReference1: c.Id.String(),
-				MerchantURLS: &CheckoutMerchantURLS{
-					Terms:        msg.Terms,
-					Checkout:     msg.Checkout,
-					Confirmation: msg.Confirmation,
-					Validation:   msg.Validation,
-					Push:         msg.Push,
-				},
-			}
-			orderPayload, err := json.Marshal(order)
-			if err != nil {
-				return nil, err
-			}
-			var klarnaOrder *CheckoutOrder
-			if c.OrderReference != "" {
-				log.Printf("Updating order id %s", c.OrderReference)
-				klarnaOrder, err = KlarnaInstance.UpdateOrder(c.OrderReference, bytes.NewReader(orderPayload))
-			} else {
-				klarnaOrder, err = KlarnaInstance.CreateOrder(bytes.NewReader(orderPayload))
-			}
-			// log.Printf("Order result: %+v", klarnaOrder)
-			if nil != err {
-				log.Printf("error from klarna: %v", err)
-				return nil, err
-			}
-			if c.OrderReference == "" {
-				c.OrderReference = klarnaOrder.ID
-				c.PaymentStatus = klarnaOrder.Status
-			}
-
-			orderData, err := json.Marshal(klarnaOrder)
-			if nil != err {
-				return nil, err
-			}
-
-			result := MakeFrameWithPayload(RemoteCreateOrderReply, 200, orderData)
-			return &result, nil
-		}
-	case OrderCompletedType:
-		msg, ok := message.Content.(*messages.OrderCreated)
-		if !ok {
-			log.Printf("expected OrderCompleted, got %T", message.Content)
-			err = fmt.Errorf("expected OrderCompleted")
-		} else {
-			c.OrderReference = msg.OrderId
-			c.PaymentStatus = msg.Status
-			c.PaymentInProgress = false
-		}
-	default:
-		err = fmt.Errorf("unknown message type %d", message.Type)
-	}
+	updated, err := ApplyRegistered(c, content)
 	if err != nil {
+		if err == ErrMutationNotRegistered {
+			return nil, fmt.Errorf("unsupported mutation type %T (not registered)", content)
+		}
 		return nil, err
 	}
 
-	if !isReplay {
-		c.mu.Lock()
-		c.storageMessages = append(c.storageMessages, *message)
-		c.mu.Unlock()
+	// Sliding TTL: update lastChange only for non-replay successful mutations.
+	if updated != nil && !isReplay {
+		c.lastChange = time.Now().Unix()
+		_ = AppendCartEvent(c.Id, content)
 	}
-	result, err := json.Marshal(c)
-	msg := MakeFrameWithPayload(RemoteHandleMutationReply, 200, result)
-	return &msg, err
+
+	return updated, nil
 }
 
 func (c *CartGrain) UpdateTotals() {

cart_id.go

@@ -0,0 +1,159 @@
+package main
+
+import (
+	"crypto/rand"
+	"encoding/json"
+	"fmt"
+)
+
+// cart_id.go
+//
+// Breaking change:
+//   Unified cart identifier as a raw 64-bit unsigned integer (type CartId uint64).
+//   External textual representation: base62 (0-9 A-Z a-z), shortest possible
+//   encoding for 64 bits (max 11 characters, since 62^11 > 2^64).
+//
+// Rationale:
+//   - Replaces legacy fixed [16]byte padded string and transitional CartID wrapper.
+//   - Provides compact, URL/cookie-friendly identifiers.
+//   - O(1) hashing and minimal memory footprint.
+//   - 64 bits of crypto randomness => negligible collision probability at realistic scale.
+//
+// Public API:
+//   type CartId uint64
+//   func NewCartId() (CartId, error)
+//   func MustNewCartId() CartId
+//   func ParseCartId(string) (CartId, bool)
+//   func MustParseCartId(string) CartId
+//   (CartId).String() string
+//   (CartId).MarshalJSON() / UnmarshalJSON()
+//
+// NOTE:
+//   All legacy helpers (UpgradeLegacyCartId, Fallback hashing, Canonicalize variants,
+//   CartIDToLegacy, LegacyToCartID) have been removed as part of the breaking change.
+//
+// ---------------------------------------------------------------------------
+
+type CartId uint64
+
+const base62Alphabet = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
+
+// Reverse lookup (0xFF marks invalid)
+var base62Rev [256]byte
+
+func init() {
+	for i := range base62Rev {
+		base62Rev[i] = 0xFF
+	}
+	for i := 0; i < len(base62Alphabet); i++ {
+		base62Rev[base62Alphabet[i]] = byte(i)
+	}
+}
+
+// String returns the canonical base62 encoding of the 64-bit id.
+func (id CartId) String() string {
+	return encodeBase62(uint64(id))
+}
+
+// MarshalJSON encodes the cart id as a JSON string.
+func (id CartId) MarshalJSON() ([]byte, error) {
+	return json.Marshal(id.String())
+}
+
+// UnmarshalJSON decodes a cart id from a JSON string containing base62 text.
+func (id *CartId) UnmarshalJSON(data []byte) error {
+	var s string
+	if err := json.Unmarshal(data, &s); err != nil {
+		return err
+	}
+	parsed, ok := ParseCartId(s)
+	if !ok {
+		return fmt.Errorf("invalid cart id: %q", s)
+	}
+	*id = parsed
+	return nil
+}
+
+// NewCartId generates a new cryptographically random non-zero 64-bit id.
+func NewCartId() (CartId, error) {
+	var b [8]byte
+	if _, err := rand.Read(b[:]); err != nil {
+		return 0, fmt.Errorf("NewCartId: %w", err)
+	}
+	u := (uint64(b[0]) << 56) |
+		(uint64(b[1]) << 48) |
+		(uint64(b[2]) << 40) |
+		(uint64(b[3]) << 32) |
+		(uint64(b[4]) << 24) |
+		(uint64(b[5]) << 16) |
+		(uint64(b[6]) << 8) |
+		uint64(b[7])
+	if u == 0 {
+		// Extremely unlikely; regenerate once to avoid "0" identifier if desired.
+		return NewCartId()
+	}
+	return CartId(u), nil
+}
+
+// MustNewCartId panics if generation fails.
+func MustNewCartId() CartId {
+	id, err := NewCartId()
+	if err != nil {
+		panic(err)
+	}
+	return id
+}
+
+// ParseCartId parses a base62 string into a CartId.
+// Returns (0,false) for invalid input.
+func ParseCartId(s string) (CartId, bool) {
+	// Accept length 1..11 (11 sufficient for 64 bits). Reject >11 immediately.
+	// Provide a slightly looser upper bound (<=16) only if you anticipate future
+	// extensions; here we stay strict.
+	if len(s) == 0 || len(s) > 11 {
+		return 0, false
+	}
+	u, ok := decodeBase62(s)
+	if !ok {
+		return 0, false
+	}
+	return CartId(u), true
+}
+
+// MustParseCartId panics on invalid base62 input.
+func MustParseCartId(s string) CartId {
+	id, ok := ParseCartId(s)
+	if !ok {
+		panic(fmt.Sprintf("invalid cart id: %q", s))
+	}
+	return id
+}
+
+// encodeBase62 converts a uint64 to base62 (shortest form).
+func encodeBase62(u uint64) string {
+	if u == 0 {
+		return "0"
+	}
+	var buf [11]byte
+	i := len(buf)
+	for u > 0 {
+		i--
+		buf[i] = base62Alphabet[u%62]
+		u /= 62
+	}
+	return string(buf[i:])
+}
+
+// decodeBase62 converts base62 text to uint64.
+func decodeBase62(s string) (uint64, bool) {
+	var v uint64
+	for i := 0; i < len(s); i++ {
+		c := s[i]
+		d := base62Rev[c]
+		if d == 0xFF {
+			return 0, false
+		}
+		v = v*62 + uint64(d)
+	}
+	return v, true
+}

cart_id_test.go

@@ -0,0 +1,185 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"testing"
+)
+
+// TestNewCartIdUniqueness generates many ids and checks for collisions.
+func TestNewCartIdUniqueness(t *testing.T) {
+	const n = 20000
+	seen := make(map[string]struct{}, n)
+	for i := 0; i < n; i++ {
+		id, err := NewCartId()
+		if err != nil {
+			t.Fatalf("NewCartId error: %v", err)
+		}
+		s := id.String()
+		if _, exists := seen[s]; exists {
+			t.Fatalf("duplicate id encountered: %s", s)
+		}
+		seen[s] = struct{}{}
+		if s == "" {
+			t.Fatalf("empty string representation for id %d", id)
+		}
+		if len(s) > 11 {
+			t.Fatalf("encoded id length exceeds 11 chars: %s (%d)", s, len(s))
+		}
+		if id == 0 {
+			// We force regeneration on zero, extremely unlikely but test guards intent.
+			t.Fatalf("zero id generated (should be regenerated)")
+		}
+	}
+}
+
+// TestParseCartIdRoundTrip ensures parse -> string -> parse is stable.
+func TestParseCartIdRoundTrip(t *testing.T) {
+	id := MustNewCartId()
+	txt := id.String()
+	parsed, ok := ParseCartId(txt)
+	if !ok {
+		t.Fatalf("ParseCartId failed for valid text %q", txt)
+	}
+	if parsed != id {
+		t.Fatalf("round trip mismatch: original=%d parsed=%d txt=%s", id, parsed, txt)
+	}
+}
+
+// TestParseCartIdInvalid covers invalid inputs.
+func TestParseCartIdInvalid(t *testing.T) {
+	invalid := []string{
+		"",               // empty
+		" ",              // space
+		"01234567890abc", // >11 chars
+		"!!!!",           // invalid chars
+		"-underscore-",   // invalid chars
+		"abc_def",        // underscore invalid for base62
+		"0123456789ABCD", // 14 chars
+	}
+	for _, s := range invalid {
+		if _, ok := ParseCartId(s); ok {
+			t.Fatalf("expected parse failure for %q", s)
+		}
+	}
+}
+
+// TestMustParseCartIdPanics verifies panic behavior for invalid input.
+func TestMustParseCartIdPanics(t *testing.T) {
+	defer func() {
+		if r := recover(); r == nil {
+			t.Fatalf("expected panic for invalid MustParseCartId input")
+		}
+	}()
+	_ = MustParseCartId("not*base62")
+}
+
+// TestJSONMarshalUnmarshalCartId verifies JSON round trip.
+func TestJSONMarshalUnmarshalCartId(t *testing.T) {
+	id := MustNewCartId()
+	data, err := json.Marshal(struct {
+		Cart CartId `json:"cart"`
+	}{Cart: id})
+	if err != nil {
+		t.Fatalf("marshal error: %v", err)
+	}
+	var out struct {
+		Cart CartId `json:"cart"`
+	}
+	if err := json.Unmarshal(data, &out); err != nil {
+		t.Fatalf("unmarshal error: %v", err)
+	}
+	if out.Cart != id {
+		t.Fatalf("JSON round trip mismatch: have %d got %d", id, out.Cart)
+	}
+}
+
+// TestBase62LengthBound checks worst-case length (near max uint64).
+func TestBase62LengthBound(t *testing.T) {
+	// Largest uint64
+	const maxU64 = ^uint64(0)
+	s := encodeBase62(maxU64)
+	if len(s) > 11 {
+		t.Fatalf("max uint64 encoded length > 11: %d (%s)", len(s), s)
+	}
+	dec, ok := decodeBase62(s)
+	if !ok || dec != maxU64 {
+		t.Fatalf("decode failed for max uint64: ok=%v dec=%d want=%d", ok, dec, maxU64)
+	}
+}
+
+// TestZeroEncoding ensures zero value encodes to "0" and parses back.
+func TestZeroEncoding(t *testing.T) {
+	if s := encodeBase62(0); s != "0" {
+		t.Fatalf("encodeBase62(0) expected '0', got %q", s)
+	}
+	v, ok := decodeBase62("0")
+	if !ok || v != 0 {
+		t.Fatalf("decodeBase62('0') failed: ok=%v v=%d", ok, v)
+	}
+	if _, ok := ParseCartId("0"); !ok {
+		t.Fatalf("ParseCartId(\"0\") should succeed")
+	}
+}
+
+// TestSequentialParse ensures sequentially generated ids parse correctly.
+func TestSequentialParse(t *testing.T) {
+	for i := 0; i < 1000; i++ {
+		id := MustNewCartId()
+		txt := id.String()
+		parsed, ok := ParseCartId(txt)
+		if !ok || parsed != id {
+			t.Fatalf("sequential parse mismatch: idx=%d orig=%d parsed=%d txt=%s", i, id, parsed, txt)
+		}
+	}
+}
+
+// BenchmarkNewCartId measures generation performance.
+func BenchmarkNewCartId(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		if _, err := NewCartId(); err != nil {
+			b.Fatalf("NewCartId error: %v", err)
+		}
+	}
+}
+
+// BenchmarkEncodeBase62 measures encoding performance.
+func BenchmarkEncodeBase62(b *testing.B) {
+	// Precompute sample values
+	samples := make([]uint64, 1024)
+	for i := range samples {
+		// Spread bits without crypto randomness overhead
+		samples[i] = (uint64(i) << 53) ^ (uint64(i) * 0x9E3779B185EBCA87)
+	}
+	b.ResetTimer()
+	var sink string
+	for i := 0; i < b.N; i++ {
+		sink = encodeBase62(samples[i%len(samples)])
+	}
+	_ = sink
+}
+
+// BenchmarkDecodeBase62 measures decoding performance.
+func BenchmarkDecodeBase62(b *testing.B) {
+	encoded := make([]string, 1024)
+	for i := range encoded {
+		encoded[i] = encodeBase62((uint64(i) << 32) | uint64(i))
+	}
+	b.ResetTimer()
+	var sum uint64
+	for i := 0; i < b.N; i++ {
+		v, ok := decodeBase62(encoded[i%len(encoded)])
+		if !ok {
+			b.Fatalf("decode failure for %s", encoded[i%len(encoded)])
+		}
+		sum ^= v
+	}
+	_ = sum
+}
+
+// ExampleCartIdString documents usage of CartId string form.
+func ExampleCartId_string() {
+	id := MustNewCartId()
+	fmt.Println(len(id.String()) <= 11) // outputs true
+	// Output: true
+}

checkout_builder.go

@@ -0,0 +1,119 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+)
+
+// CheckoutMeta carries the external / URL metadata required to build a
+// Klarna CheckoutOrder from a CartGrain snapshot. It deliberately excludes
+// any Klarna-specific response fields (HTML snippet, client token, etc.).
+type CheckoutMeta struct {
+	Terms        string
+	Checkout     string
+	Confirmation string
+	Validation   string
+	Push         string
+	Country      string
+	Currency     string // optional override (defaults to "SEK" if empty)
+	Locale       string // optional override (defaults to "sv-se" if empty)
+}
+
+// BuildCheckoutOrderPayload converts the current cart grain + meta information
+// into a CheckoutOrder domain struct and returns its JSON-serialized payload
+// (to send to Klarna) alongside the structured CheckoutOrder object.
+//
+// This function is PURE: it does not perform any network I/O or mutate the
+// grain. The caller is responsible for:
+//
+//  1. Choosing whether to create or update the Klarna order.
+//  2. Invoking KlarnaClient.CreateOrder / UpdateOrder with the returned payload.
+//  3. Applying an InitializeCheckout mutation (or equivalent) with the
+//     resulting Klarna order id + status.
+//
+// If you later need to support different tax rates per line, you can extend
+// CartItem / Delivery to expose that data and propagate it here.
+func BuildCheckoutOrderPayload(grain *CartGrain, meta *CheckoutMeta) ([]byte, *CheckoutOrder, error) {
+	if grain == nil {
+		return nil, nil, fmt.Errorf("nil grain")
+	}
+	if meta == nil {
+		return nil, nil, fmt.Errorf("nil checkout meta")
+	}
+
+	currency := meta.Currency
+	if currency == "" {
+		currency = "SEK"
+	}
+	locale := meta.Locale
+	if locale == "" {
+		locale = "sv-se"
+	}
+	country := meta.Country
+	if country == "" {
+		country = "SE" // sensible default; adjust if multi-country support changes
+	}
+
+	lines := make([]*Line, 0, len(grain.Items)+len(grain.Deliveries))
+
+	// Item lines
+	for _, it := range grain.Items {
+		if it == nil {
+			continue
+		}
+		lines = append(lines, &Line{
+			Type:           "physical",
+			Reference:      it.Sku,
+			Name:           it.Name,
+			Quantity:       it.Quantity,
+			UnitPrice:      int(it.Price),
+			TaxRate:        2500, // TODO: derive if variable tax rates are introduced
+			QuantityUnit:   "st",
+			TotalAmount:    int(it.TotalPrice),
+			TotalTaxAmount: int(it.TotalTax),
+			ImageURL:       fmt.Sprintf("https://www.elgiganten.se%s", it.Image),
+		})
+	}
+
+	// Delivery lines
+	for _, d := range grain.Deliveries {
+		if d == nil || d.Price <= 0 {
+			continue
+		}
+		lines = append(lines, &Line{
+			Type:           "shipping_fee",
+			Reference:      d.Provider,
+			Name:           "Delivery",
+			Quantity:       1,
+			UnitPrice:      int(d.Price),
+			TaxRate:        2500,
+			QuantityUnit:   "st",
+			TotalAmount:    int(d.Price),
+			TotalTaxAmount: int(GetTaxAmount(d.Price, 2500)),
+		})
+	}
+
+	order := &CheckoutOrder{
+		PurchaseCountry:    country,
+		PurchaseCurrency:   currency,
+		Locale:             locale,
+		OrderAmount:        int(grain.TotalPrice),
+		OrderTaxAmount:     int(grain.TotalTax),
+		OrderLines:         lines,
+		MerchantReference1: grain.Id.String(),
+		MerchantURLS: &CheckoutMerchantURLS{
+			Terms:        meta.Terms,
+			Checkout:     meta.Checkout,
+			Confirmation: meta.Confirmation,
+			Validation:   meta.Validation,
+			Push:         meta.Push,
+		},
+	}
+
+	payload, err := json.Marshal(order)
+	if err != nil {
+		return nil, nil, fmt.Errorf("marshal checkout order: %w", err)
+	}
+
+	return payload, order, nil
+}

cookies.txt

@@ -0,0 +1,5 @@
+# Netscape HTTP Cookie File
+# https://curl.se/docs/http-cookies.html
+# This file was generated by libcurl! Edit at your own risk.
+
+#HttpOnly_localhost	FALSE	/	FALSE	1761304670	cartid	4393545184291837

deployment/deployment-no.yaml

@@ -1,276 +0,0 @@
-apiVersion: v1
-kind: Secret
-metadata:
-  name:  klarna-api-credentials
-data:
-  username: ZjQzZDY3YjEtNzA2Yy00NTk2LTliNTgtYjg1YjU2NDEwZTUw
-  password: a2xhcm5hX3Rlc3RfYXBpX0trUWhWVE5yYVZsV2FsTnhTRVp3Y1ZSSFF5UkVNRmxyY25Kd1AxSndQMGdzWmpRelpEWTNZakV0TnpBMll5MDBOVGsyTFRsaU5UZ3RZamcxWWpVMk5ERXdaVFV3TERFc2JUUkNjRFpWU1RsTllsSk1aMlEyVEc4MmRVODNZMkozUlRaaFdEZDViV3AwYkhGV1JqTjVNQzlaYXow
-type: Opaque
----
-apiVersion: apps/v1
-kind: Deployment
-metadata:
-  labels:
-    app: cart-actor
-    arch: amd64
-  name: cart-actor-x86
-spec:
-  replicas: 0
-  selector:
-    matchLabels:
-      app: cart-actor
-      arch: amd64
-  template:
-    metadata:
-      labels:
-        app: cart-actor
-        actor-pool: cart
-        arch: amd64
-    spec:
-      affinity:
-        nodeAffinity:
-          requiredDuringSchedulingIgnoredDuringExecution:
-            nodeSelectorTerms:
-              - matchExpressions:
-                - key: kubernetes.io/arch
-                  operator: NotIn
-                  values:
-                    - arm64
-      volumes:
-        - name: data
-          nfs:
-            path: /i-data/7a8af061/nfs/cart-actor-no
-            server: 10.10.1.10
-      imagePullSecrets:
-        - name: regcred
-      serviceAccountName: default
-      containers:
-        - image: registry.knatofs.se/go-cart-actor-amd64:latest
-          name: cart-actor-amd64
-          imagePullPolicy: Always
-          lifecycle:
-            preStop:
-              exec:
-                command: ["sleep", "15"]
-          ports:
-            - containerPort: 8080
-              name: web
-            - containerPort: 1234
-              name: echo
-            - containerPort: 1337
-              name: rpc
-            - containerPort: 1338
-              name: quorum
-          livenessProbe:
-            httpGet:
-              path: /livez
-              port: web
-            failureThreshold: 1
-            periodSeconds: 10
-          readinessProbe:
-            httpGet:
-              path: /readyz
-              port: web
-            failureThreshold: 2
-            initialDelaySeconds: 2
-            periodSeconds: 10
-          volumeMounts:
-            - mountPath: "/data"
-              name: data
-          resources:
-            limits:
-              memory: "768Mi"
-            requests:
-              memory: "70Mi"
-              cpu: "1200m"
-          env:
-            - name: TZ
-              value: "Europe/Stockholm"
-            - name: KLARNA_API_USERNAME
-              valueFrom:
-                secretKeyRef:
-                  name: klarna-api-credentials
-                  key: username
-            - name: KLARNA_API_PASSWORD
-              valueFrom:
-                secretKeyRef:
-                  name: klarna-api-credentials
-                  key: password
-            - name: POD_IP
-              valueFrom:
-                fieldRef:
-                  fieldPath: status.podIP
-            - name: AMQP_URL
-              value: "amqp://admin:12bananer@rabbitmq.dev:5672/"
-            - name: BASE_URL
-              value: "https://s10n-no.tornberg.me"
-            - name: CART_BASE_URL
-              value: "https://cart-no.tornberg.me"
-            - name: POD_NAME
-              valueFrom:
-                fieldRef:
-                  fieldPath: metadata.name
----
-apiVersion: apps/v1
-kind: Deployment
-metadata:
-  labels:
-    app: cart-actor
-    arch: arm64
-  name: cart-actor-arm64
-spec:
-  replicas: 3
-  selector:
-    matchLabels:
-      app: cart-actor
-      arch: arm64
-  template:
-    metadata:
-      labels:
-        app: cart-actor
-        actor-pool: cart
-        arch: arm64
-    spec:
-      affinity:
-        nodeAffinity:
-          requiredDuringSchedulingIgnoredDuringExecution:
-            nodeSelectorTerms:
-              - matchExpressions:
-                - key: kubernetes.io/hostname
-                  operator: NotIn
-                  values:
-                    - masterpi
-                - key: kubernetes.io/arch
-                  operator: In
-                  values:
-                    - arm64
-      volumes:
-        - name: data
-          nfs:
-            path: /i-data/7a8af061/nfs/cart-actor-no
-            server: 10.10.1.10
-      imagePullSecrets:
-        - name: regcred
-      serviceAccountName: default
-      containers:
-        - image: registry.knatofs.se/go-cart-actor:latest
-          name: cart-actor-arm64
-          imagePullPolicy: Always
-          lifecycle:
-            preStop:
-              exec:
-                command: ["sleep", "15"]
-          ports:
-            - containerPort: 8080
-              name: web
-            - containerPort: 1234
-              name: echo
-            - containerPort: 1337
-              name: rpc
-            - containerPort: 1338
-              name: quorum
-          livenessProbe:
-            httpGet:
-              path: /livez
-              port: web
-            failureThreshold: 1
-            periodSeconds: 10
-          readinessProbe:
-            httpGet:
-              path: /readyz
-              port: web
-            failureThreshold: 2
-            initialDelaySeconds: 2
-            periodSeconds: 10
-          volumeMounts:
-            - mountPath: "/data"
-              name: data
-          resources:
-            limits:
-              memory: "768Mi"
-            requests:
-              memory: "70Mi"
-              cpu: "1200m"
-          env:
-            - name: TZ
-              value: "Europe/Stockholm"
-            - name: KLARNA_API_USERNAME
-              valueFrom:
-                secretKeyRef:
-                  name: klarna-api-credentials
-                  key: username
-            - name: KLARNA_API_PASSWORD
-              valueFrom:
-                secretKeyRef:
-                  name: klarna-api-credentials
-                  key: password
-            - name: POD_IP
-              valueFrom:
-                fieldRef:
-                  fieldPath: status.podIP
-            - name: AMQP_URL
-              value: "amqp://admin:12bananer@rabbitmq.dev:5672/"
-            - name: BASE_URL
-              value: "https://s10n-no.tornberg.me"
-            - name: CART_BASE_URL
-              value: "https://cart-no.tornberg.me"
-            - name: POD_NAME
-              valueFrom:
-                fieldRef:
-                  fieldPath: metadata.name
----
-kind: Service
-apiVersion: v1
-metadata:
-  name: cart-echo
-spec:
-  selector:
-    app: cart-actor
-  type: LoadBalancer
-  ports:
-    - name: echo
-      port: 1234
----
-kind: Service
-apiVersion: v1
-metadata:
-  name: cart-actor
-  annotations:
-    prometheus.io/port: "8080"
-    prometheus.io/scrape: "true"
-    prometheus.io/path: "/metrics"
-spec:
-  selector:
-    app: cart-actor
-  ports:
-    - name: web
-      port: 8080
----
-apiVersion: networking.k8s.io/v1
-kind: Ingress
-metadata:
-  name: cart-ingress
-  annotations:
-    cert-manager.io/cluster-issuer: letsencrypt-prod
-    # nginx.ingress.kubernetes.io/affinity: "cookie"
-    # nginx.ingress.kubernetes.io/session-cookie-name: "cart-affinity"
-    # nginx.ingress.kubernetes.io/session-cookie-expires: "172800"
-    # nginx.ingress.kubernetes.io/session-cookie-max-age: "172800"
-    nginx.ingress.kubernetes.io/proxy-body-size: 4m
-spec:
-  ingressClassName: nginx
-  tls:
-    - hosts:
-        - cart-no.tornberg.me
-      secretName: cart-actor-no-tls-secret
-  rules:
-    - host: cart-no.tornberg.me
-      http:
-        paths:
-          - path: /
-            pathType: Prefix
-            backend:
-              service:
-                name: cart-actor
-                port:
-                  number: 8080

deployment/deployment.yaml

@@ -1,272 +1,252 @@
 apiVersion: v1
 kind: Secret
 metadata:
-  name:  klarna-api-credentials
+    name: klarna-api-credentials
 data:
-  username: ZjQzZDY3YjEtNzA2Yy00NTk2LTliNTgtYjg1YjU2NDEwZTUw
-  password: a2xhcm5hX3Rlc3RfYXBpX0trUWhWVE5yYVZsV2FsTnhTRVp3Y1ZSSFF5UkVNRmxyY25Kd1AxSndQMGdzWmpRelpEWTNZakV0TnpBMll5MDBOVGsyTFRsaU5UZ3RZamcxWWpVMk5ERXdaVFV3TERFc2JUUkNjRFpWU1RsTllsSk1aMlEyVEc4MmRVODNZMkozUlRaaFdEZDViV3AwYkhGV1JqTjVNQzlaYXow
+    username: ZjQzZDY3YjEtNzA2Yy00NTk2LTliNTgtYjg1YjU2NDEwZTUw
+    password: a2xhcm5hX3Rlc3RfYXBpX0trUWhWVE5yYVZsV2FsTnhTRVp3Y1ZSSFF5UkVNRmxyY25Kd1AxSndQMGdzWmpRelpEWTNZakV0TnpBMll5MDBOVGsyTFRsaU5UZ3RZamcxWWpVMk5ERXdaVFV3TERFc2JUUkNjRFpWU1RsTllsSk1aMlEyVEc4MmRVODNZMkozUlRaaFdEZDViV3AwYkhGV1JqTjVNQzlaYXow
 type: Opaque
 ---
 apiVersion: apps/v1
 kind: Deployment
 metadata:
-  labels:
-    app: cart-actor
-    arch: amd64
-  name: cart-actor-x86
-spec:
-  replicas: 0
-  selector:
-    matchLabels:
-      app: cart-actor
-      arch: amd64
-  template:
-    metadata:
-      labels:
+    labels:
         app: cart-actor
-        actor-pool: cart
         arch: amd64
-    spec:
-      affinity:
-        nodeAffinity:
-          requiredDuringSchedulingIgnoredDuringExecution:
-            nodeSelectorTerms:
-              - matchExpressions:
-                - key: kubernetes.io/arch
-                  operator: NotIn
-                  values:
-                    - arm64
-      volumes:
-        - name: data
-          nfs:
-            path: /i-data/7a8af061/nfs/cart-actor
-            server: 10.10.1.10
-      imagePullSecrets:
-        - name: regcred
-      serviceAccountName: default
-      containers:
-        - image: registry.knatofs.se/go-cart-actor-amd64:latest
-          name: cart-actor-amd64
-          imagePullPolicy: Always
-          lifecycle:
-            preStop:
-              exec:
-                command: ["sleep", "15"]
-          ports:
-            - containerPort: 8080
-              name: web
-            - containerPort: 1234
-              name: echo
-            - containerPort: 1337
-              name: rpc
-            - containerPort: 1338
-              name: quorum
-          livenessProbe:
-            httpGet:
-              path: /livez
-              port: web
-            failureThreshold: 1
-            periodSeconds: 10
-          readinessProbe:
-            httpGet:
-              path: /readyz
-              port: web
-            failureThreshold: 2
-            initialDelaySeconds: 2
-            periodSeconds: 10
-          volumeMounts:
-            - mountPath: "/data"
-              name: data
-          resources:
-            limits:
-              memory: "768Mi"
-            requests:
-              memory: "70Mi"
-              cpu: "1200m"
-          env:
-            - name: TZ
-              value: "Europe/Stockholm"
-            - name: KLARNA_API_USERNAME
-              valueFrom:
-                secretKeyRef:
-                  name: klarna-api-credentials
-                  key: username
-            - name: KLARNA_API_PASSWORD
-              valueFrom:
-                secretKeyRef:
-                  name: klarna-api-credentials
-                  key: password
-            - name: POD_IP
-              valueFrom:
-                fieldRef:
-                  fieldPath: status.podIP
-            - name: AMQP_URL
-              value: "amqp://admin:12bananer@rabbitmq.dev:5672/"
-            # - name: BASE_URL
-            #   value: "https://s10n-no.tornberg.me"
-            - name: POD_NAME
-              valueFrom:
-                fieldRef:
-                  fieldPath: metadata.name
+    name: cart-actor-x86
+spec:
+    replicas: 0
+    selector:
+        matchLabels:
+            app: cart-actor
+            arch: amd64
+    template:
+        metadata:
+            labels:
+                app: cart-actor
+                actor-pool: cart
+                arch: amd64
+        spec:
+            affinity:
+                nodeAffinity:
+                    requiredDuringSchedulingIgnoredDuringExecution:
+                        nodeSelectorTerms:
+                            - matchExpressions:
+                                  - key: kubernetes.io/arch
+                                    operator: NotIn
+                                    values:
+                                        - arm64
+            volumes:
+                - name: data
+                  nfs:
+                      path: /i-data/7a8af061/nfs/cart-actor
+                      server: 10.10.1.10
+            imagePullSecrets:
+                - name: regcred
+            serviceAccountName: default
+            containers:
+                - image: registry.knatofs.se/go-cart-actor-amd64:latest
+                  name: cart-actor-amd64
+                  imagePullPolicy: Always
+                  lifecycle:
+                      preStop:
+                          exec:
+                              command: ["sleep", "15"]
+                  ports:
+                      - containerPort: 8080
+                        name: web
+                      - containerPort: 1337
+                        name: rpc
+                  livenessProbe:
+                      httpGet:
+                          path: /livez
+                          port: web
+                      failureThreshold: 1
+                      periodSeconds: 10
+                  readinessProbe:
+                      httpGet:
+                          path: /readyz
+                          port: web
+                      failureThreshold: 2
+                      initialDelaySeconds: 2
+                      periodSeconds: 10
+                  volumeMounts:
+                      - mountPath: "/data"
+                        name: data
+                  resources:
+                      limits:
+                          memory: "768Mi"
+                      requests:
+                          memory: "70Mi"
+                          cpu: "1200m"
+                  env:
+                      - name: TZ
+                        value: "Europe/Stockholm"
+                      - name: KLARNA_API_USERNAME
+                        valueFrom:
+                            secretKeyRef:
+                                name: klarna-api-credentials
+                                key: username
+                      - name: KLARNA_API_PASSWORD
+                        valueFrom:
+                            secretKeyRef:
+                                name: klarna-api-credentials
+                                key: password
+                      - name: POD_IP
+                        valueFrom:
+                            fieldRef:
+                                fieldPath: status.podIP
+                      - name: AMQP_URL
+                        value: "amqp://admin:12bananer@rabbitmq.dev:5672/"
+                      # - name: BASE_URL
+                      #   value: "https://s10n-no.tornberg.me"
+                      - name: POD_NAME
+                        valueFrom:
+                            fieldRef:
+                                fieldPath: metadata.name
 ---
 apiVersion: apps/v1
 kind: Deployment
 metadata:
-  labels:
-    app: cart-actor
-    arch: arm64
-  name: cart-actor-arm64
-spec:
-  replicas: 0
-  selector:
-    matchLabels:
-      app: cart-actor
-      arch: arm64
-  template:
-    metadata:
-      labels:
+    labels:
         app: cart-actor
-        actor-pool: cart
         arch: arm64
-    spec:
-      affinity:
-        nodeAffinity:
-          requiredDuringSchedulingIgnoredDuringExecution:
-            nodeSelectorTerms:
-              - matchExpressions:
-                - key: kubernetes.io/hostname
-                  operator: NotIn
-                  values:
-                    - masterpi
-                - key: kubernetes.io/arch
-                  operator: In
-                  values:
-                    - arm64
-      volumes:
-        - name: data
-          nfs:
-            path: /i-data/7a8af061/nfs/cart-actor
-            server: 10.10.1.10
-      imagePullSecrets:
-        - name: regcred
-      serviceAccountName: default
-      containers:
-        - image: registry.knatofs.se/go-cart-actor:latest
-          name: cart-actor-arm64
-          imagePullPolicy: Always
-          lifecycle:
-            preStop:
-              exec:
-                command: ["sleep", "15"]
-          ports:
-            - containerPort: 8080
-              name: web
-            - containerPort: 1234
-              name: echo
-            - containerPort: 1337
-              name: rpc
-            - containerPort: 1338
-              name: quorum
-          livenessProbe:
-            httpGet:
-              path: /livez
-              port: web
-            failureThreshold: 1
-            periodSeconds: 10
-          readinessProbe:
-            httpGet:
-              path: /readyz
-              port: web
-            failureThreshold: 2
-            initialDelaySeconds: 2
-            periodSeconds: 10
-          volumeMounts:
-            - mountPath: "/data"
-              name: data
-          resources:
-            limits:
-              memory: "768Mi"
-            requests:
-              memory: "70Mi"
-              cpu: "1200m"
-          env:
-            - name: TZ
-              value: "Europe/Stockholm"
-            - name: KLARNA_API_USERNAME
-              valueFrom:
-                secretKeyRef:
-                  name: klarna-api-credentials
-                  key: username
-            - name: KLARNA_API_PASSWORD
-              valueFrom:
-                secretKeyRef:
-                  name: klarna-api-credentials
-                  key: password
-            - name: POD_IP
-              valueFrom:
-                fieldRef:
-                  fieldPath: status.podIP
-            - name: AMQP_URL
-              value: "amqp://admin:12bananer@rabbitmq.dev:5672/"
-            # - name: BASE_URL
-            #   value: "https://s10n-no.tornberg.me"
-            - name: POD_NAME
-              valueFrom:
-                fieldRef:
-                  fieldPath: metadata.name
+    name: cart-actor-arm64
+spec:
+    replicas: 3
+    selector:
+        matchLabels:
+            app: cart-actor
+            arch: arm64
+    template:
+        metadata:
+            labels:
+                app: cart-actor
+                actor-pool: cart
+                arch: arm64
+        spec:
+            affinity:
+                nodeAffinity:
+                    requiredDuringSchedulingIgnoredDuringExecution:
+                        nodeSelectorTerms:
+                            - matchExpressions:
+                                  - key: kubernetes.io/hostname
+                                    operator: NotIn
+                                    values:
+                                        - masterpi
+                                  - key: kubernetes.io/arch
+                                    operator: In
+                                    values:
+                                        - arm64
+            volumes:
+                - name: data
+                  nfs:
+                      path: /i-data/7a8af061/nfs/cart-actor
+                      server: 10.10.1.10
+            imagePullSecrets:
+                - name: regcred
+            serviceAccountName: default
+            containers:
+                - image: registry.knatofs.se/go-cart-actor:latest
+                  name: cart-actor-arm64
+                  imagePullPolicy: Always
+                  lifecycle:
+                      preStop:
+                          exec:
+                              command: ["sleep", "15"]
+                  ports:
+                      - containerPort: 8080
+                        name: web
+                      - containerPort: 1337
+                        name: rpc
+                  livenessProbe:
+                      httpGet:
+                          path: /livez
+                          port: web
+                      failureThreshold: 1
+                      periodSeconds: 10
+                  readinessProbe:
+                      httpGet:
+                          path: /readyz
+                          port: web
+                      failureThreshold: 2
+                      initialDelaySeconds: 2
+                      periodSeconds: 10
+                  volumeMounts:
+                      - mountPath: "/data"
+                        name: data
+                  resources:
+                      limits:
+                          memory: "768Mi"
+                      requests:
+                          memory: "70Mi"
+                          cpu: "1200m"
+                  env:
+                      - name: TZ
+                        value: "Europe/Stockholm"
+                      - name: KLARNA_API_USERNAME
+                        valueFrom:
+                            secretKeyRef:
+                                name: klarna-api-credentials
+                                key: username
+                      - name: KLARNA_API_PASSWORD
+                        valueFrom:
+                            secretKeyRef:
+                                name: klarna-api-credentials
+                                key: password
+                      - name: POD_IP
+                        valueFrom:
+                            fieldRef:
+                                fieldPath: status.podIP
+                      - name: AMQP_URL
+                        value: "amqp://admin:12bananer@rabbitmq.dev:5672/"
+                      # - name: BASE_URL
+                      #   value: "https://s10n-no.tornberg.me"
+                      - name: POD_NAME
+                        valueFrom:
+                            fieldRef:
+                                fieldPath: metadata.name
 ---
 kind: Service
 apiVersion: v1
 metadata:
-  name: cart-echo
+    name: cart-actor
+    annotations:
+        prometheus.io/port: "8080"
+        prometheus.io/scrape: "true"
+        prometheus.io/path: "/metrics"
 spec:
-  selector:
-    app: cart-actor
-  type: LoadBalancer
-  ports:
-    - name: echo
-      port: 1234
----
-kind: Service
-apiVersion: v1
-metadata:
-  name: cart-actor
-  annotations:
-    prometheus.io/port: "8080"
-    prometheus.io/scrape: "true"
-    prometheus.io/path: "/metrics"
-spec:
-  selector:
-    app: cart-actor
-  ports:
-    - name: web
-      port: 8080
+    selector:
+        app: cart-actor
+    ports:
+        - name: web
+          port: 8080
 ---
 apiVersion: networking.k8s.io/v1
 kind: Ingress
 metadata:
-  name: cart-ingress
-  annotations:
-    cert-manager.io/cluster-issuer: letsencrypt-prod
-    # nginx.ingress.kubernetes.io/affinity: "cookie"
-    # nginx.ingress.kubernetes.io/session-cookie-name: "cart-affinity"
-    # nginx.ingress.kubernetes.io/session-cookie-expires: "172800"
-    # nginx.ingress.kubernetes.io/session-cookie-max-age: "172800"
-    nginx.ingress.kubernetes.io/proxy-body-size: 4m
+    name: cart-ingress
+    annotations:
+        cert-manager.io/cluster-issuer: letsencrypt-prod
+        nginx.ingress.kubernetes.io/affinity: "cookie"
+        nginx.ingress.kubernetes.io/session-cookie-name: "cart-affinity"
+        nginx.ingress.kubernetes.io/session-cookie-expires: "172800"
+        nginx.ingress.kubernetes.io/session-cookie-max-age: "172800"
+        nginx.ingress.kubernetes.io/proxy-body-size: 4m
 spec:
-  ingressClassName: nginx
-  tls:
-    - hosts:
-        - cart.tornberg.me
-      secretName: cart-actor-tls-secret
-  rules:
-    - host: cart.tornberg.me
-      http:
-        paths:
-          - path: /
-            pathType: Prefix
-            backend:
-              service:
-                name: cart-actor
-                port:
-                  number: 8080
+    ingressClassName: nginx
+    tls:
+        - hosts:
+              - cart.tornberg.me
+          secretName: cart-actor-tls-secret
+    rules:
+        - host: cart.tornberg.me
+          http:
+              paths:
+                  - path: /
+                    pathType: Prefix
+                    backend:
+                        service:
+                            name: cart-actor
+                            port:
+                                number: 8080

deployment/scaling.yaml

@@ -1,25 +1,101 @@
-apiVersion: autoscaling/v1
+apiVersion: autoscaling/v2
 kind: HorizontalPodAutoscaler
 metadata:
-  name: cart-scaler-amd
+    name: cart-scaler-amd
 spec:
-  scaleTargetRef:
-    apiVersion: apps/v1
-    kind: Deployment
-    name: cart-actor-x86
-  minReplicas: 3
-  maxReplicas: 9
-  targetCPUUtilizationPercentage: 30
+    scaleTargetRef:
+        apiVersion: apps/v1
+        kind: Deployment
+        name: cart-actor-x86
+    minReplicas: 3
+    maxReplicas: 9
+    behavior:
+        scaleUp:
+            stabilizationWindowSeconds: 60
+            policies:
+                - type: Percent
+                  value: 100
+                  periodSeconds: 60
+        scaleDown:
+            stabilizationWindowSeconds: 180
+            policies:
+                - type: Percent
+                  value: 50
+                  periodSeconds: 60
+    metrics:
+        - type: Resource
+          resource:
+              name: cpu
+              target:
+                  type: Utilization
+                  averageUtilization: 50
+        # Future custom metric (example):
+        # - type: Pods
+        #   pods:
+        #     metric:
+        #       name: cart_mutations_per_second
+        #     target:
+        #       type: AverageValue
+        #       averageValue: "15"
+        # - type: Object
+        #   object:
+        #     describedObject:
+        #       apiVersion: networking.k8s.io/v1
+        #       kind: Ingress
+        #       name: cart-ingress
+        #     metric:
+        #       name: http_requests_per_second
+        #     target:
+        #       type: Value
+        #       value: "100"
 ---
-apiVersion: autoscaling/v1
+apiVersion: autoscaling/v2
 kind: HorizontalPodAutoscaler
 metadata:
-  name: cart-scaler-arm
+    name: cart-scaler-arm
 spec:
-  scaleTargetRef:
-    apiVersion: apps/v1
-    kind: Deployment
-    name: cart-actor-arm64
-  minReplicas: 3
-  maxReplicas: 9
-  targetCPUUtilizationPercentage: 30
+    scaleTargetRef:
+        apiVersion: apps/v1
+        kind: Deployment
+        name: cart-actor-arm64
+    minReplicas: 3
+    maxReplicas: 9
+    behavior:
+        scaleUp:
+            stabilizationWindowSeconds: 60
+            policies:
+                - type: Percent
+                  value: 100
+                  periodSeconds: 60
+        scaleDown:
+            stabilizationWindowSeconds: 180
+            policies:
+                - type: Percent
+                  value: 50
+                  periodSeconds: 60
+    metrics:
+        - type: Resource
+          resource:
+              name: cpu
+              target:
+                  type: Utilization
+                  averageUtilization: 50
+        # Future custom metric (example):
+        # - type: Pods
+        #   pods:
+        #     metric:
+        #       name: cart_mutations_per_second
+        #     target:
+        #       type: AverageValue
+        #       averageValue: "15"
+        # - type: Object
+        #   object:
+        #     describedObject:
+        #       apiVersion: networking.k8s.io/v1
+        #       kind: Ingress
+        #       name: cart-ingress
+        #     metric:
+        #       name: http_requests_per_second
+        #     target:
+        #       type: Value
+        #       value: "100"

discovery.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"context"
+	"sync"
 
 	v1 "k8s.io/api/core/v1"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
@@ -75,3 +76,97 @@ func NewK8sDiscovery(client *kubernetes.Clientset) *K8sDiscovery {
 		client: client,
 	}
 }
+
+// MockDiscovery is an in-memory Discovery implementation for tests.
+// It allows deterministic injection of host additions/removals without
+// depending on Kubernetes API machinery.
+type MockDiscovery struct {
+	mu      sync.RWMutex
+	hosts   []string
+	events  chan HostChange
+	closed  bool
+	started bool
+}
+
+// NewMockDiscovery creates a mock discovery with an initial host list.
+func NewMockDiscovery(initial []string) *MockDiscovery {
+	cp := make([]string, len(initial))
+	copy(cp, initial)
+	return &MockDiscovery{
+		hosts:  cp,
+		events: make(chan HostChange, 32),
+	}
+}
+
+// Discover returns the current host snapshot.
+func (m *MockDiscovery) Discover() ([]string, error) {
+	m.mu.RLock()
+	defer m.mu.RUnlock()
+	cp := make([]string, len(m.hosts))
+	copy(cp, m.hosts)
+	return cp, nil
+}
+
+// Watch returns a channel that will receive HostChange events.
+// The channel is buffered; AddHost/RemoveHost push events non-blockingly.
+func (m *MockDiscovery) Watch() (<-chan HostChange, error) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	if m.closed {
+		return nil, context.Canceled
+	}
+	m.started = true
+	return m.events, nil
+}
+
+// AddHost inserts a new host (if absent) and emits an Added event.
+func (m *MockDiscovery) AddHost(host string) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	if m.closed {
+		return
+	}
+	for _, h := range m.hosts {
+		if h == host {
+			return
+		}
+	}
+	m.hosts = append(m.hosts, host)
+	if m.started {
+		m.events <- HostChange{Host: host, Type: watch.Added}
+	}
+}
+
+// RemoveHost removes a host (if present) and emits a Deleted event.
+func (m *MockDiscovery) RemoveHost(host string) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	if m.closed {
+		return
+	}
+	idx := -1
+	for i, h := range m.hosts {
+		if h == host {
+			idx = i
+			break
+		}
+	}
+	if idx == -1 {
+		return
+	}
+	m.hosts = append(m.hosts[:idx], m.hosts[idx+1:]...)
+	if m.started {
+		m.events <- HostChange{Host: host, Type: watch.Deleted}
+	}
+}
+
+// Close closes the event channel (idempotent).
+func (m *MockDiscovery) Close() {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	if m.closed {
+		return
+	}
+	m.closed = true
+	close(m.events)
+}

disk-storage.go

@@ -2,118 +2,72 @@ package main
 
 import (
 	"encoding/gob"
-	"fmt"
-	"log"
-	"os"
 	"time"
 )
 
+func init() {
+
+	gob.Register(map[uint64]int64{})
+}
+
 type DiskStorage struct {
 	stateFile string
 	lastSave  int64
-	LastSaves map[CartId]int64
+	LastSaves map[uint64]int64
 }
 
 func NewDiskStorage(stateFile string) (*DiskStorage, error) {
 	ret := &DiskStorage{
 		stateFile: stateFile,
-		LastSaves: make(map[CartId]int64),
+		LastSaves: make(map[uint64]int64),
 	}
-	err := ret.loadState()
-	return ret, err
+	//err := ret.loadState()
+	return ret, nil
 }
 
-func saveMessages(messages []StorableMessage, id CartId) error {
+// func saveMessages(_ interface{}, _ CartId) error {
+// 	// No-op: legacy event log persistence removed in oneof refactor.
+// 	return nil
+// }
 
-	if len(messages) == 0 {
-		return nil
-	}
-	log.Printf("%d messages to save for grain id %s", len(messages), id)
-	var file *os.File
-	var err error
-	path := getCartPath(id.String())
-	file, err = os.OpenFile(path, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)
-	if err != nil {
-		return err
-	}
-	defer file.Close()
+// func getCartPath(id string) string {
+// 	return fmt.Sprintf("data/%s.prot", id)
+// }
 
-	for _, m := range messages {
-		err := m.Write(file)
-		if err != nil {
-			return err
-		}
-	}
-	return err
-}
+// func loadMessages(_ Grain, _ CartId) error {
+// 	// No-op: legacy replay removed in oneof refactor.
+// 	return nil
+// }
 
-func getCartPath(id string) string {
-	return fmt.Sprintf("data/%s.prot", id)
-}
+// func (s *DiskStorage) saveState() error {
+// 	tmpFile := s.stateFile + "_tmp"
+// 	file, err := os.Create(tmpFile)
+// 	if err != nil {
+// 		return err
+// 	}
+// 	defer file.Close()
+// 	err = gob.NewEncoder(file).Encode(s.LastSaves)
+// 	if err != nil {
+// 		return err
+// 	}
+// 	os.Remove(s.stateFile + ".bak")
+// 	os.Rename(s.stateFile, s.stateFile+".bak")
+// 	return os.Rename(tmpFile, s.stateFile)
+// }
 
-func loadMessages(grain Grain, id CartId) error {
-	var err error
-	path := getCartPath(id.String())
+// func (s *DiskStorage) loadState() error {
+// 	file, err := os.Open(s.stateFile)
+// 	if err != nil {
+// 		return err
+// 	}
+// 	defer file.Close()
+// 	return gob.NewDecoder(file).Decode(&s.LastSaves)
+// }
 
-	file, err := os.Open(path)
-	if err != nil {
-		if os.IsNotExist(err) {
-			return nil
-		}
-		return err
-	}
-	defer file.Close()
-
-	for err == nil {
-		var msg Message
-		err = ReadMessage(file, &msg)
-		if err == nil {
-			grain.HandleMessage(&msg, true)
-		}
-	}
-
-	if err.Error() == "EOF" {
-		return nil
-	}
-	return err
-}
-
-func (s *DiskStorage) saveState() error {
-	tmpFile := s.stateFile + "_tmp"
-	file, err := os.Create(tmpFile)
-	if err != nil {
-		return err
-	}
-	defer file.Close()
-	err = gob.NewEncoder(file).Encode(s.LastSaves)
-	if err != nil {
-		return err
-	}
-	os.Remove(s.stateFile + ".bak")
-	os.Rename(s.stateFile, s.stateFile+".bak")
-	return os.Rename(tmpFile, s.stateFile)
-}
-
-func (s *DiskStorage) loadState() error {
-	file, err := os.Open(s.stateFile)
-	if err != nil {
-		return err
-	}
-	defer file.Close()
-	return gob.NewDecoder(file).Decode(&s.LastSaves)
-}
-
-func (s *DiskStorage) Store(id CartId, grain *CartGrain) error {
-	lastSavedMessage, ok := s.LastSaves[id]
-	if ok && lastSavedMessage > grain.GetLastChange() {
-		return nil
-	}
-	err := saveMessages(grain.GetStorageMessage(lastSavedMessage), id)
-	if err != nil {
-		return err
-	}
+func (s *DiskStorage) Store(id CartId, _ *CartGrain) error {
+	// With the removal of the legacy message log, we only update the timestamp.
 	ts := time.Now().Unix()
-	s.LastSaves[id] = ts
+	s.LastSaves[uint64(id)] = ts
 	s.lastSave = ts
 	return nil
 }

event_log.go

@@ -0,0 +1,288 @@
+package main
+
+import (
+	"bufio"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"os"
+	"path/filepath"
+	"reflect"
+	"sync"
+	"time"
+
+	messages "git.tornberg.me/go-cart-actor/proto"
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promauto"
+)
+
+/*
+event_log.go
+
+Append-only cart event log (per cart id) with replay + metrics.
+
+Rationale:
+  - Enables recovery of in-memory cart state after process restarts or TTL eviction.
+  - Provides a chronological mutation trail for auditing / debugging.
+  - Avoids write amplification of full snapshots on every mutation.
+
+Format:
+  One JSON object per line:
+   {
+     "ts": 1700000000,
+     "type": "AddRequest",
+     "payload": { ... mutation fields ... }
+   }
+
+Concurrency:
+  - Appends: synchronized per-cart via an in-process mutex map to avoid partial writes.
+  - Replay: sequential read of entire file; mutations applied in order.
+
+Usage Integration (to be wired by caller):
+  1. After successful mutation application (non-replay), invoke:
+        AppendCartEvent(grain.GetId(), mutation)
+  2. During grain spawn, call:
+        ReplayCartEvents(grain, grain.GetId())
+     BEFORE serving requests, so state is reconstructed.
+
+Metrics:
+  - cart_event_log_appends_total
+  - cart_event_log_replay_total
+  - cart_event_log_replay_failures_total
+  - cart_event_log_bytes_written_total
+  - cart_event_log_files_existing (gauge)
+  - cart_event_log_last_append_unix (gauge)
+  - cart_event_log_replay_duration_seconds (histogram)
+
+Rotation / Compaction:
+  - Not implemented. If needed, implement size checks and snapshot+truncate later.
+
+Caveats:
+  - Mutation schema changes may break replay unless backward-compatible.
+  - Missing / unknown event types are skipped (metric incremented).
+  - If a mutation fails during replay, replay continues (logged + metric).
+
+*/
+
+var (
+	eventLogDir = "data"
+
+	eventAppendsTotal = promauto.NewCounter(prometheus.CounterOpts{
+		Name: "cart_event_log_appends_total",
+		Help: "Total number of cart mutation events appended to event logs.",
+	})
+	eventReplayTotal = promauto.NewCounter(prometheus.CounterOpts{
+		Name: "cart_event_log_replay_total",
+		Help: "Total number of successful event log replays (per cart).",
+	})
+	eventReplayFailuresTotal = promauto.NewCounter(prometheus.CounterOpts{
+		Name: "cart_event_log_replay_failures_total",
+		Help: "Total number of failed event log replay operations.",
+	})
+	eventBytesWrittenTotal = promauto.NewCounter(prometheus.CounterOpts{
+		Name: "cart_event_log_bytes_written_total",
+		Help: "Cumulative number of bytes written to all cart event logs.",
+	})
+	eventFilesExisting = promauto.NewGauge(prometheus.GaugeOpts{
+		Name: "cart_event_log_files_existing",
+		Help: "Number of cart event log files currently existing on disk.",
+	})
+	eventLastAppendUnix = promauto.NewGauge(prometheus.GaugeOpts{
+		Name: "cart_event_log_last_append_unix",
+		Help: "Unix timestamp of the last append to any cart event log.",
+	})
+	eventReplayDuration = promauto.NewHistogram(prometheus.HistogramOpts{
+		Name:    "cart_event_log_replay_duration_seconds",
+		Help:    "Duration of replay operations per cart in seconds.",
+		Buckets: prometheus.DefBuckets,
+	})
+	eventUnknownTypesTotal = promauto.NewCounter(prometheus.CounterOpts{
+		Name: "cart_event_log_unknown_types_total",
+		Help: "Total number of unknown event types encountered during replay (skipped).",
+	})
+	eventMutationErrorsTotal = promauto.NewCounter(prometheus.CounterOpts{
+		Name: "cart_event_log_mutation_errors_total",
+		Help: "Total number of errors applying mutation events during replay.",
+	})
+)
+
+type cartEventRecord struct {
+	Timestamp int64       `json:"ts"`
+	Type      string      `json:"type"`
+	Payload   interface{} `json:"payload"`
+}
+
+// registry of supported mutation payload type constructors
+var eventTypeFactories = map[string]func() interface{}{
+	"AddRequest":         func() interface{} { return &messages.AddRequest{} },
+	"AddItem":            func() interface{} { return &messages.AddItem{} },
+	"RemoveItem":         func() interface{} { return &messages.RemoveItem{} },
+	"RemoveDelivery":     func() interface{} { return &messages.RemoveDelivery{} },
+	"ChangeQuantity":     func() interface{} { return &messages.ChangeQuantity{} },
+	"SetDelivery":        func() interface{} { return &messages.SetDelivery{} },
+	"SetPickupPoint":     func() interface{} { return &messages.SetPickupPoint{} },
+	"SetCartRequest":     func() interface{} { return &messages.SetCartRequest{} },
+	"OrderCreated":       func() interface{} { return &messages.OrderCreated{} },
+	"InitializeCheckout": func() interface{} { return &messages.InitializeCheckout{} },
+}
+
+// Per-cart mutexes to serialize append operations (avoid partial overlapping writes)
+var (
+	eventLogMu sync.Map // map[string]*sync.Mutex
+)
+
+// getCartEventMutex returns a mutex for a specific cart id string.
+func getCartEventMutex(id string) *sync.Mutex {
+	if v, ok := eventLogMu.Load(id); ok {
+		return v.(*sync.Mutex)
+	}
+	m := &sync.Mutex{}
+	actual, _ := eventLogMu.LoadOrStore(id, m)
+	return actual.(*sync.Mutex)
+}
+
+// EventLogPath returns the path to the cart's event log file.
+func EventLogPath(id CartId) string {
+	return filepath.Join(eventLogDir, fmt.Sprintf("%s.events.log", id.String()))
+}
+
+// EnsureEventLogDirectory ensures base directory exists and updates gauge.
+func EnsureEventLogDirectory() error {
+	if _, err := os.Stat(eventLogDir); errors.Is(err, os.ErrNotExist) {
+		if err2 := os.MkdirAll(eventLogDir, 0755); err2 != nil {
+			return err2
+		}
+	}
+	// Update files existing gauge (approximate; counts matching *.events.log)
+	pattern := filepath.Join(eventLogDir, "*.events.log")
+	matches, _ := filepath.Glob(pattern)
+	eventFilesExisting.Set(float64(len(matches)))
+	return nil
+}
+
+// AppendCartEvent appends a mutation event to the cart's log (JSON line).
+func AppendCartEvent(id CartId, mutation interface{}) error {
+	if mutation == nil {
+		return errors.New("nil mutation cannot be logged")
+	}
+	if err := EnsureEventLogDirectory(); err != nil {
+		return err
+	}
+
+	typ := mutationTypeName(mutation)
+	rec := cartEventRecord{
+		Timestamp: time.Now().Unix(),
+		Type:      typ,
+		Payload:   mutation,
+	}
+	lineBytes, err := json.Marshal(rec)
+	if err != nil {
+		return fmt.Errorf("marshal event: %w", err)
+	}
+	lineBytes = append(lineBytes, '\n')
+
+	path := EventLogPath(id)
+	mtx := getCartEventMutex(id.String())
+	mtx.Lock()
+	defer mtx.Unlock()
+
+	fh, err := os.OpenFile(path, os.O_CREATE|os.O_APPEND|os.O_WRONLY, 0644)
+	if err != nil {
+		return fmt.Errorf("open event log: %w", err)
+	}
+	defer fh.Close()
+
+	n, werr := fh.Write(lineBytes)
+	if werr != nil {
+		return fmt.Errorf("write event log: %w", werr)
+	}
+
+	eventAppendsTotal.Inc()
+	eventBytesWrittenTotal.Add(float64(n))
+	eventLastAppendUnix.Set(float64(rec.Timestamp))
+	return nil
+}
+
+// ReplayCartEvents replays an existing cart's event log into the provided grain.
+// It applies mutation payloads in order, skipping unknown types.
+func ReplayCartEvents(grain *CartGrain, id CartId) error {
+	start := time.Now()
+	path := EventLogPath(id)
+	if _, err := os.Stat(path); errors.Is(err, os.ErrNotExist) {
+		// No log -> nothing to replay
+		return nil
+	}
+
+	fh, err := os.Open(path)
+	if err != nil {
+		eventReplayFailuresTotal.Inc()
+		return fmt.Errorf("open replay file: %w", err)
+	}
+	defer fh.Close()
+
+	scanner := bufio.NewScanner(fh)
+	// Increase buffer in case of large payloads
+	const maxLine = 256 * 1024
+	buf := make([]byte, 0, 64*1024)
+	scanner.Buffer(buf, maxLine)
+
+	for scanner.Scan() {
+		line := scanner.Bytes()
+		var raw struct {
+			Timestamp int64           `json:"ts"`
+			Type      string          `json:"type"`
+			Payload   json.RawMessage `json:"payload"`
+		}
+		if err := json.Unmarshal(line, &raw); err != nil {
+			eventReplayFailuresTotal.Inc()
+			continue // skip malformed line
+		}
+		factory, ok := eventTypeFactories[raw.Type]
+		if !ok {
+			eventUnknownTypesTotal.Inc()
+			continue // skip unknown mutation type
+		}
+		instance := factory()
+		if err := json.Unmarshal(raw.Payload, instance); err != nil {
+			eventMutationErrorsTotal.Inc()
+			continue
+		}
+		// Apply mutation directly using internal registration (bypass AppendCartEvent recursion).
+		if _, applyErr := ApplyRegistered(grain, instance); applyErr != nil {
+			eventMutationErrorsTotal.Inc()
+			continue
+		} else {
+			// Update lastChange to the timestamp of this event (sliding inactivity window support).
+			grain.lastChange = raw.Timestamp
+		}
+	}
+	if serr := scanner.Err(); serr != nil {
+		eventReplayFailuresTotal.Inc()
+		return fmt.Errorf("scanner error: %w", serr)
+	}
+
+	eventReplayTotal.Inc()
+	eventReplayDuration.Observe(time.Since(start).Seconds())
+	return nil
+}
+
+// mutationTypeName returns the short struct name for a mutation (pointer aware).
+func mutationTypeName(v interface{}) string {
+	if v == nil {
+		return "nil"
+	}
+	t := reflect.TypeOf(v)
+	if t.Kind() == reflect.Ptr {
+		t = t.Elem()
+	}
+	return t.Name()
+}
+
+/*
+Future enhancements:
+  - Compression: gzip large (> N events) logs to reduce disk usage.
+  - Compaction: periodic snapshot + truncate old events to bound replay latency.
+  - Checkpoint events: inject cart state snapshots every M mutations.
+  - Integrity: add checksum per line for corruption detection.
+  - Multi-writer safety across processes (currently only safe within one process).
+*/

frames.go

@@ -1,102 +0,0 @@
-package main
-
-// Minimal frame abstractions retained after removal of the legacy TCP/frame
-// networking layer. These types remain only to avoid a wide cascading refactor
-// across existing grain / pool logic that still constructs and passes
-// FrameWithPayload objects internally.
-//
-// The original responsibilities this replaces:
-//   - Binary framing, checksums, network IO
-//   - Distinction between request / reply frame types
-//
-// What remains:
-//   - A light weight container (FrameWithPayload) used as an in‑process
-//     envelope for status code + typed marker + payload bytes (JSON or proto).
-//   - Message / status constants referenced in existing code paths.
-//
-// Recommended future cleanup (post‑migration):
-//   - Remove FrameType entirely and replace with enumerated semantic results
-//     or error values.
-//   - Replace FrameWithPayload with a struct { Status int; Data []byte }.
-//   - Remove remote_* reply type branching once all callers rely on gRPC
-//     status + strongly typed responses.
-//
-// For now we keep this minimal surface to keep the gRPC migration focused.
-
-type (
-	// FrameType is a symbolic identifier carried through existing code paths.
-	// No ordering or bit semantics are required anymore.
-	FrameType  uint32
-	StatusCode uint32
-)
-
-type Frame struct {
-	Type       FrameType
-	StatusCode StatusCode
-	Length     uint32
-	// Checksum retained for compatibility; no longer validated.
-	Checksum uint32
-}
-
-// FrameWithPayload wraps a Frame with an opaque payload.
-// Payload usually contains JSON encoded cart state or an error message.
-type FrameWithPayload struct {
-	Frame
-	Payload []byte
-}
-
-// -----------------------------------------------------------------------------
-// Legacy Frame Type Constants (minimal subset still referenced)
-// -----------------------------------------------------------------------------
-const (
-	RemoteGetState            = FrameType(0x01)
-	RemoteHandleMutation      = FrameType(0x02)
-	ResponseBody              = FrameType(0x03) // (rarely used; kept for completeness)
-	RemoteGetStateReply       = FrameType(0x04)
-	RemoteHandleMutationReply = FrameType(0x05)
-	RemoteCreateOrderReply    = FrameType(0x06)
-)
-
-// MakeFrameWithPayload constructs an in‑process frame wrapper.
-// Length & Checksum are filled for backward compatibility (no validation logic
-// depends on the checksum anymore).
-func MakeFrameWithPayload(msg FrameType, statusCode StatusCode, payload []byte) FrameWithPayload {
-	length := uint32(len(payload))
-	return FrameWithPayload{
-		Frame: Frame{
-			Type:       msg,
-			StatusCode: statusCode,
-			Length:     length,
-			Checksum:   (uint32(msg) + uint32(statusCode) + length) / 8, // simple legacy formula
-		},
-		Payload: payload,
-	}
-}
-
-// Clone creates a shallow copy of the frame, duplicating the payload slice.
-func (f *FrameWithPayload) Clone() *FrameWithPayload {
-	if f == nil {
-		return nil
-	}
-	cp := make([]byte, len(f.Payload))
-	copy(cp, f.Payload)
-	return &FrameWithPayload{
-		Frame:   f.Frame,
-		Payload: cp,
-	}
-}
-
-// NewErrorFrame helper for creating an error frame with a textual payload.
-func NewErrorFrame(msg FrameType, code StatusCode, err error) FrameWithPayload {
-	var b []byte
-	if err != nil {
-		b = []byte(err.Error())
-	}
-	return MakeFrameWithPayload(msg, code, b)
-}
-
-// IsSuccess returns true if the status code indicates success in the
-// conventional HTTP style range (200–299). This mirrors previous usage patterns.
-func (f *FrameWithPayload) IsSuccess() bool {
-	return f != nil && f.StatusCode >= 200 && f.StatusCode < 300
-}

grafana_dashboard_cart.json

@@ -0,0 +1,327 @@
+{
+  "uid": "cart-actors",
+  "title": "Cart Actor Cluster",
+  "timezone": "browser",
+  "refresh": "30s",
+  "schemaVersion": 38,
+  "version": 1,
+  "editable": true,
+  "graphTooltip": 0,
+  "panels": [
+    {
+      "type": "row",
+      "title": "Overview",
+      "gridPos": { "x": 0, "y": 0, "w": 24, "h": 1 },
+      "id": 1,
+      "collapsed": false
+    },
+    {
+      "type": "stat",
+      "title": "Active Grains",
+      "id": 2,
+      "gridPos": { "x": 0, "y": 1, "w": 6, "h": 4 },
+      "datasource": "${DS_PROMETHEUS}",
+      "targets": [
+        { "refId": "A", "expr": "cart_active_grains" }
+      ],
+      "options": {
+        "colorMode": "value",
+        "graphMode": "none",
+        "justifyMode": "center",
+        "reduceOptions": { "calcs": ["lastNotNull"], "fields": "", "values": false }
+      }
+    },
+    {
+      "type": "stat",
+      "title": "Grains In Pool",
+      "id": 3,
+      "gridPos": { "x": 6, "y": 1, "w": 6, "h": 4 },
+      "datasource": "${DS_PROMETHEUS}",
+      "targets": [
+        { "refId": "A", "expr": "cart_grains_in_pool" }
+      ],
+      "options": {
+        "colorMode": "value",
+        "graphMode": "none",
+        "justifyMode": "center",
+        "reduceOptions": { "calcs": ["lastNotNull"], "fields": "", "values": false }
+      }
+    },
+    {
+      "type": "stat",
+      "title": "Pool Usage %",
+      "id": 4,
+      "gridPos": { "x": 12, "y": 1, "w": 6, "h": 4 },
+      "datasource": "${DS_PROMETHEUS}",
+      "targets": [
+        { "refId": "A", "expr": "cart_grain_pool_usage * 100" }
+      ],
+      "units": "percent",
+      "options": {
+        "colorMode": "value",
+        "graphMode": "none",
+        "justifyMode": "center",
+        "reduceOptions": { "calcs": ["lastNotNull"] }
+      }
+    },
+    {
+      "type": "stat",
+      "title": "Connected Remotes",
+      "id": 5,
+      "gridPos": { "x": 18, "y": 1, "w": 6, "h": 4 },
+      "datasource": "${DS_PROMETHEUS}",
+      "targets": [
+        { "refId": "A", "expr": "connected_remotes" }
+      ],
+      "options": {
+        "colorMode": "value",
+        "graphMode": "none",
+        "justifyMode": "center",
+        "reduceOptions": { "calcs": ["lastNotNull"] }
+      }
+    },
+
+    {
+      "type": "row",
+      "title": "Mutations",
+      "gridPos": { "x": 0, "y": 5, "w": 24, "h": 1 },
+      "id": 6,
+      "collapsed": false
+    },
+    {
+      "type": "timeseries",
+      "title": "Mutation Rate (1m)",
+      "id": 7,
+      "gridPos": { "x": 0, "y": 6, "w": 12, "h": 8 },
+      "datasource": "${DS_PROMETHEUS}",
+      "targets": [
+        { "refId": "A", "expr": "rate(cart_mutations_total[1m])", "legendFormat": "mutations/s" },
+        { "refId": "B", "expr": "rate(cart_mutation_failures_total[1m])", "legendFormat": "failures/s" }
+      ],
+      "fieldConfig": { "defaults": { "unit": "ops" } }
+    },
+    {
+      "type": "stat",
+      "title": "Failure % (5m)",
+      "id": 8,
+      "gridPos": { "x": 12, "y": 6, "w": 6, "h": 4 },
+      "datasource": "${DS_PROMETHEUS}",
+      "targets": [
+        {
+          "refId": "A",
+          "expr": "100 * (increase(cart_mutation_failures_total[5m]) / clamp_max(increase(cart_mutations_total[5m]), 1))"
+        }
+      ],
+      "options": {
+        "colorMode": "value",
+        "graphMode": "none",
+        "justifyMode": "center",
+        "reduceOptions": { "calcs": ["lastNotNull"] }
+      }
+    },
+    {
+      "type": "timeseries",
+      "title": "Mutation Latency Quantiles",
+      "id": 9,
+      "gridPos": { "x": 18, "y": 6, "w": 6, "h": 8 },
+      "datasource": "${DS_PROMETHEUS}",
+      "targets": [
+        {
+          "refId": "A",
+          "expr": "histogram_quantile(0.50, sum(rate(cart_mutation_latency_seconds_bucket[5m])) by (le))",
+          "legendFormat": "p50"
+        },
+        {
+          "refId": "B",
+          "expr": "histogram_quantile(0.90, sum(rate(cart_mutation_latency_seconds_bucket[5m])) by (le))",
+          "legendFormat": "p90"
+        },
+        {
+          "refId": "C",
+          "expr": "histogram_quantile(0.99, sum(rate(cart_mutation_latency_seconds_bucket[5m])) by (le))",
+          "legendFormat": "p99"
+        }
+      ],
+      "fieldConfig": { "defaults": { "unit": "s" } }
+    },
+
+    {
+      "type": "row",
+      "title": "Event Log",
+      "gridPos": { "x": 0, "y": 14, "w": 24, "h": 1 },
+      "id": 10,
+      "collapsed": false
+    },
+    {
+      "type": "timeseries",
+      "title": "Event Append Rate (5m)",
+      "id": 11,
+      "gridPos": { "x": 0, "y": 15, "w": 8, "h": 6 },
+      "datasource": "${DS_PROMETHEUS}",
+      "targets": [
+        { "refId": "A", "expr": "rate(cart_event_log_appends_total[5m])", "legendFormat": "appends/s" }
+      ]
+    },
+    {
+      "type": "timeseries",
+      "title": "Event Bytes Written Rate (5m)",
+      "id": 12,
+      "gridPos": { "x": 8, "y": 15, "w": 8, "h": 6 },
+      "datasource": "${DS_PROMETHEUS}",
+      "targets": [
+        { "refId": "A", "expr": "rate(cart_event_log_bytes_written_total[5m])", "legendFormat": "bytes/s" }
+      ],
+      "fieldConfig": { "defaults": { "unit": "Bps" } }
+    },
+    {
+      "type": "stat",
+      "title": "Existing Log Files",
+      "id": 13,
+      "gridPos": { "x": 16, "y": 15, "w": 4, "h": 3 },
+      "datasource": "${DS_PROMETHEUS}",
+      "targets": [{ "refId": "A", "expr": "cart_event_log_files_existing" }],
+      "options": { "reduceOptions": { "calcs": ["lastNotNull"] } }
+    },
+    {
+      "type": "stat",
+      "title": "Last Append Age (s)",
+      "id": 14,
+      "gridPos": { "x": 20, "y": 15, "w": 4, "h": 3 },
+      "datasource": "${DS_PROMETHEUS}",
+      "targets": [
+        { "refId": "A", "expr": "(time() - cart_event_log_last_append_unix)" }
+      ],
+      "options": { "reduceOptions": { "calcs": ["lastNotNull"] } }
+    },
+    {
+      "type": "stat",
+      "title": "Replay Failures Total",
+      "id": 15,
+      "gridPos": { "x": 16, "y": 18, "w": 4, "h": 3 },
+      "datasource": "${DS_PROMETHEUS}",
+      "targets": [{ "refId": "A", "expr": "cart_event_log_replay_failures_total" }],
+      "options": { "reduceOptions": { "calcs": ["lastNotNull"] } }
+    },
+    {
+      "type": "stat",
+      "title": "Replay Duration p95 (5m)",
+      "id": 16,
+      "gridPos": { "x": 20, "y": 18, "w": 4, "h": 3 },
+      "datasource": "${DS_PROMETHEUS}",
+      "targets": [
+        {
+          "refId": "A",
+            "expr": "histogram_quantile(0.95, sum(rate(cart_event_log_replay_duration_seconds_bucket[5m])) by (le))"
+        }
+      ],
+      "options": { "reduceOptions": { "calcs": ["lastNotNull"] }, "fieldConfig": { "defaults": { "unit": "s" } } }
+    },
+
+    {
+      "type": "row",
+      "title": "Grain Lifecycle",
+      "gridPos": { "x": 0, "y": 21, "w": 24, "h": 1 },
+      "id": 17,
+      "collapsed": false
+    },
+    {
+      "type": "timeseries",
+      "title": "Spawn & Lookup Rates (1m)",
+      "id": 18,
+      "gridPos": { "x": 0, "y": 22, "w": 12, "h": 8 },
+      "datasource": "${DS_PROMETHEUS}",
+      "targets": [
+        { "refId": "A", "expr": "rate(cart_grain_spawned_total[1m])", "legendFormat": "spawns/s" },
+        { "refId": "B", "expr": "rate(cart_grain_lookups_total[1m])", "legendFormat": "lookups/s" }
+      ]
+    },
+    {
+      "type": "stat",
+      "title": "Negotiations Rate (5m)",
+      "id": 19,
+      "gridPos": { "x": 12, "y": 22, "w": 6, "h": 4 },
+      "datasource": "${DS_PROMETHEUS}",
+      "targets": [
+        { "refId": "A", "expr": "rate(cart_remote_negotiation_total[5m])" }
+      ],
+      "options": { "reduceOptions": { "calcs": ["lastNotNull"] }, "orientation": "horizontal" }
+    },
+    {
+      "type": "stat",
+      "title": "Mutations Total",
+      "id": 20,
+      "gridPos": { "x": 18, "y": 22, "w": 6, "h": 4 },
+      "datasource": "${DS_PROMETHEUS}",
+      "targets": [{ "refId": "A", "expr": "cart_mutations_total" }],
+      "options": { "reduceOptions": { "calcs": ["lastNotNull"] } }
+    },
+
+    {
+      "type": "row",
+      "title": "Event Log Errors",
+      "gridPos": { "x": 0, "y": 30, "w": 24, "h": 1 },
+      "id": 21,
+      "collapsed": false
+    },
+    {
+      "type": "stat",
+      "title": "Unknown Event Types",
+      "id": 22,
+      "gridPos": { "x": 0, "y": 31, "w": 6, "h": 4 },
+      "datasource": "${DS_PROMETHEUS}",
+      "targets": [{ "refId": "A", "expr": "cart_event_log_unknown_types_total" }],
+      "options": { "reduceOptions": { "calcs": ["lastNotNull"] } }
+    },
+    {
+      "type": "stat",
+      "title": "Event Mutation Errors",
+      "id": 23,
+      "gridPos": { "x": 6, "y": 31, "w": 6, "h": 4 },
+      "datasource": "${DS_PROMETHEUS}",
+      "targets": [{ "refId": "A", "expr": "cart_event_log_mutation_errors_total" }],
+      "options": { "reduceOptions": { "calcs": ["lastNotNull"] } }
+    },
+    {
+      "type": "stat",
+      "title": "Replay Success Total",
+      "id": 24,
+      "gridPos": { "x": 12, "y": 31, "w": 6, "h": 4 },
+      "datasource": "${DS_PROMETHEUS}",
+      "targets": [{ "refId": "A", "expr": "cart_event_log_replay_total" }],
+      "options": { "reduceOptions": { "calcs": ["lastNotNull"] } }
+    },
+    {
+      "type": "stat",
+      "title": "Replay Duration p50 (5m)",
+      "id": 25,
+      "gridPos": { "x": 18, "y": 31, "w": 6, "h": 4 },
+      "datasource": "${DS_PROMETHEUS}",
+      "targets": [
+        {
+          "refId": "A",
+          "expr": "histogram_quantile(0.50, sum(rate(cart_event_log_replay_duration_seconds_bucket[5m])) by (le))"
+        }
+      ],
+      "options": { "reduceOptions": { "calcs": ["lastNotNull"] }, "fieldConfig": { "defaults": { "unit": "s" } } }
+    }
+  ],
+  "templating": {
+    "list": [
+      {
+        "name": "DS_PROMETHEUS",
+        "label": "Prometheus",
+        "type": "datasource",
+        "query": "prometheus",
+        "current": { "text": "Prometheus", "value": "Prometheus" }
+      }
+    ]
+  },
+  "time": {
+    "from": "now-6h",
+    "to": "now"
+  },
+  "timepicker": {
+    "refresh_intervals": ["5s","10s","30s","1m","5m","15m","30m","1h"],
+    "time_options": ["5m","15m","30m","1h","6h","12h","24h","2d","7d"]
+  }
+}

grain-pool.go

@@ -1,168 +1,827 @@
 package main
 
 import (
-	"encoding/json"
+	"bytes"
+	"context"
 	"fmt"
+	"io"
 	"log"
+	"net/http"
+	"reflect"
 	"sync"
 	"time"
 
+	messages "git.tornberg.me/go-cart-actor/proto"
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/client_golang/prometheus/promauto"
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/credentials/insecure"
+	"k8s.io/apimachinery/pkg/watch"
 )
 
+// ---------------------------------------------------------------------------
+// Metrics shared by the cart pool implementation.
+// ---------------------------------------------------------------------------
+
 var (
 	poolGrains = promauto.NewGauge(prometheus.GaugeOpts{
 		Name: "cart_grains_in_pool",
-		Help: "The total number of grains in the pool",
+		Help: "The total number of grains in the local pool",
 	})
 	poolSize = promauto.NewGauge(prometheus.GaugeOpts{
 		Name: "cart_pool_size",
-		Help: "The total number of mutations",
+		Help: "Configured capacity of the cart pool",
 	})
 	poolUsage = promauto.NewGauge(prometheus.GaugeOpts{
 		Name: "cart_grain_pool_usage",
-		Help: "The current usage of the grain pool",
+		Help: "Current utilisation of the cart pool",
+	})
+	negotiationCount = promauto.NewCounter(prometheus.CounterOpts{
+		Name: "cart_remote_negotiation_total",
+		Help: "The total number of remote host negotiations",
+	})
+	connectedRemotes = promauto.NewGauge(prometheus.GaugeOpts{
+		Name: "cart_connected_remotes",
+		Help: "Number of connected remote hosts",
+	})
+	cartMutationsTotal = promauto.NewCounter(prometheus.CounterOpts{
+		Name: "cart_mutations_total",
+		Help: "Total number of cart state mutations applied",
+	})
+	cartMutationFailuresTotal = promauto.NewCounter(prometheus.CounterOpts{
+		Name: "cart_mutation_failures_total",
+		Help: "Total number of failed cart state mutations",
+	})
+	cartMutationLatencySeconds = promauto.NewHistogramVec(prometheus.HistogramOpts{
+		Name:    "cart_mutation_latency_seconds",
+		Help:    "Latency of cart mutations in seconds",
+		Buckets: prometheus.DefBuckets,
+	}, []string{"mutation"})
+	cartActiveGrains = promauto.NewGauge(prometheus.GaugeOpts{
+		Name: "cart_active_grains",
+		Help: "Number of active (resident) local grains",
 	})
 )
 
+// GrainPool is the interface exposed to HTTP handlers and other subsystems.
 type GrainPool interface {
-	Process(id CartId, messages ...Message) (*FrameWithPayload, error)
-	Get(id CartId) (*FrameWithPayload, error)
+	Apply(id CartId, mutation interface{}) (*CartGrain, error)
+	Get(id CartId) (*CartGrain, error)
+	OwnerHost(id CartId) (Host, bool)
+	Hostname() string
+	TakeOwnership(id CartId)
+	IsHealthy() bool
+	Close()
 }
 
+// Host abstracts a remote node capable of proxying cart requests.
+type Host interface {
+	Name() string
+	Proxy(id CartId, w http.ResponseWriter, r *http.Request) (bool, error)
+}
+
+// Ttl tracks the expiry deadline for an in-memory grain.
 type Ttl struct {
 	Expires time.Time
 	Grain   *CartGrain
 }
 
-type GrainLocalPool struct {
-	mu       sync.RWMutex
-	grains   map[CartId]*CartGrain
+// CartPool merges the responsibilities that previously belonged to
+// GrainLocalPool and SyncedPool. It provides local grain storage together
+// with cluster coordination, ownership negotiation and expiry signalling.
+type CartPool struct {
+	// Local grain state -----------------------------------------------------
+	localMu  sync.RWMutex
+	grains   map[uint64]*CartGrain
 	expiry   []Ttl
 	spawn    func(id CartId) (*CartGrain, error)
-	Ttl      time.Duration
-	PoolSize int
+	ttl      time.Duration
+	poolSize int
+
+	// Cluster coordination --------------------------------------------------
+	hostname             string
+	remoteMu             sync.RWMutex
+	remoteOwners         map[CartId]*RemoteHostGRPC
+	remoteHosts          map[string]*RemoteHostGRPC
+	discardedHostHandler *DiscardedHostHandler
+
+	// House-keeping ---------------------------------------------------------
+	purgeTicker *time.Ticker
 }
 
-func NewGrainLocalPool(size int, ttl time.Duration, spawn func(id CartId) (*CartGrain, error)) *GrainLocalPool {
+// RemoteHostGRPC mirrors the lightweight controller used for remote node
+// interaction.
+type RemoteHostGRPC struct {
+	Host          string
+	HTTPBase      string
+	Conn          *grpc.ClientConn
+	Transport     *http.Transport
+	Client        *http.Client
+	ControlClient messages.ControlPlaneClient
+	MissedPings   int
+}
 
-	ret := &GrainLocalPool{
-		spawn:    spawn,
-		grains:   make(map[CartId]*CartGrain),
-		expiry:   make([]Ttl, 0),
-		Ttl:      ttl,
-		PoolSize: size,
+func (h *RemoteHostGRPC) Name() string {
+	return h.Host
+}
+
+func (h *RemoteHostGRPC) Proxy(id CartId, w http.ResponseWriter, r *http.Request) (bool, error) {
+	target := fmt.Sprintf("%s%s", h.HTTPBase, r.URL.RequestURI())
+	var bodyCopy []byte
+	if r.Body != nil && r.Body != http.NoBody {
+		var err error
+		bodyCopy, err = io.ReadAll(r.Body)
+		if err != nil {
+			http.Error(w, "proxy read error", http.StatusBadGateway)
+			return false, err
+		}
+	}
+	if r.Body != nil {
+		r.Body.Close()
+	}
+	var reqBody io.Reader
+	if len(bodyCopy) > 0 {
+		reqBody = bytes.NewReader(bodyCopy)
+	}
+	req, err := http.NewRequestWithContext(r.Context(), r.Method, target, reqBody)
+	if err != nil {
+		http.Error(w, "proxy build error", http.StatusBadGateway)
+		return false, err
+	}
+	r.Body = io.NopCloser(bytes.NewReader(bodyCopy))
+	req.Header.Set("X-Forwarded-Host", r.Host)
+	if idStr := id.String(); idStr != "" {
+		req.Header.Set("X-Cart-Id", idStr)
+	}
+	for k, v := range r.Header {
+		for _, vv := range v {
+			req.Header.Add(k, vv)
+		}
+	}
+	res, err := h.Client.Do(req)
+	if err != nil {
+		http.Error(w, "proxy request error", http.StatusBadGateway)
+		return false, err
+	}
+	defer res.Body.Close()
+	for k, v := range res.Header {
+		for _, vv := range v {
+			w.Header().Add(k, vv)
+		}
+	}
+	w.Header().Set("X-Cart-Owner-Routed", "true")
+	if res.StatusCode >= 200 && res.StatusCode <= 299 {
+		w.WriteHeader(res.StatusCode)
+		_, copyErr := io.Copy(w, res.Body)
+		if copyErr != nil {
+			return true, copyErr
+		}
+		return true, nil
+	}
+	return false, fmt.Errorf("proxy response status %d", res.StatusCode)
+}
+
+func (r *RemoteHostGRPC) IsHealthy() bool {
+	return r.MissedPings < 3
+}
+
+// NewCartPool constructs a unified pool. Discovery may be nil for standalone
+// deployments.
+func NewCartPool(size int, ttl time.Duration, hostname string, spawn func(id CartId) (*CartGrain, error), discovery Discovery) (*CartPool, error) {
+	p := &CartPool{
+		grains:       make(map[uint64]*CartGrain),
+		expiry:       make([]Ttl, 0),
+		spawn:        spawn,
+		ttl:          ttl,
+		poolSize:     size,
+		hostname:     hostname,
+		remoteOwners: make(map[CartId]*RemoteHostGRPC),
+		remoteHosts:  make(map[string]*RemoteHostGRPC),
 	}
 
-	cartPurge := time.NewTicker(time.Minute)
+	p.discardedHostHandler = NewDiscardedHostHandler(1338)
+	p.discardedHostHandler.SetReconnectHandler(p.AddRemote)
+
+	p.purgeTicker = time.NewTicker(time.Minute)
 	go func() {
-		<-cartPurge.C
-		ret.Purge()
+		for range p.purgeTicker.C {
+			p.Purge()
+		}
 	}()
-	return ret
+
+	if discovery != nil {
+		go p.startDiscovery(discovery)
+	} else {
+		log.Printf("No discovery configured; expecting manual AddRemote or static host injection")
+	}
+
+	return p, nil
 }
 
-func (p *GrainLocalPool) SetAvailable(availableWithLastChangeUnix map[CartId]int64) {
-	p.mu.Lock()
-	defer p.mu.Unlock()
-	for id := range availableWithLastChangeUnix {
-		if _, ok := p.grains[id]; !ok {
-			p.grains[id] = nil
-			p.expiry = append(p.expiry, Ttl{
-				Expires: time.Now().Add(p.Ttl),
-				Grain:   nil,
-			})
+// startDiscovery subscribes to cluster events and adds/removes hosts.
+func (p *CartPool) startDiscovery(discovery Discovery) {
+	time.Sleep(3 * time.Second) // allow gRPC server startup
+	log.Printf("Starting discovery watcher")
+	ch, err := discovery.Watch()
+	if err != nil {
+		log.Printf("Discovery error: %v", err)
+		return
+	}
+	for evt := range ch {
+		if evt.Host == "" {
+			continue
+		}
+		switch evt.Type {
+		case watch.Deleted:
+			if p.IsKnown(evt.Host) {
+				p.RemoveHost(evt.Host)
+			}
+		default:
+			if !p.IsKnown(evt.Host) {
+				log.Printf("Discovered host %s", evt.Host)
+				p.AddRemote(evt.Host)
+			}
 		}
 	}
 }
 
-func (p *GrainLocalPool) Purge() {
-	lastChangeTime := time.Now().Add(-p.Ttl)
-	keepChanged := lastChangeTime.Unix()
-	p.mu.Lock()
-	defer p.mu.Unlock()
-	for i := 0; i < len(p.expiry); i++ {
-		item := p.expiry[i]
-		if item.Expires.Before(time.Now()) {
-			if item.Grain.GetLastChange() > keepChanged {
-				log.Printf("Expired item %s changed, keeping", item.Grain.GetId())
-				if i < len(p.expiry)-1 {
-					p.expiry = append(p.expiry[:i], p.expiry[i+1:]...)
-					p.expiry = append(p.expiry, item)
-				} else {
-					p.expiry = append(p.expiry[:i], item)
-				}
+// ---------------------------------------------------------------------------
+// Local grain management
+// ---------------------------------------------------------------------------
 
-			} else {
-				log.Printf("Item %s expired", item.Grain.GetId())
-				delete(p.grains, item.Grain.GetId())
-				if i < len(p.expiry)-1 {
-					p.expiry = append(p.expiry[:i], p.expiry[i+1:]...)
-				} else {
-					p.expiry = p.expiry[:i]
-				}
-			}
+func (p *CartPool) statsUpdate() {
+	p.localMu.RLock()
+	size := len(p.grains)
+	cap := p.poolSize
+	p.localMu.RUnlock()
+	poolGrains.Set(float64(size))
+	poolSize.Set(float64(cap))
+	if cap > 0 {
+		poolUsage.Set(float64(size) / float64(cap))
+	}
+}
+
+// LocalUsage returns the number of resident grains and configured capacity.
+func (p *CartPool) LocalUsage() (int, int) {
+	p.localMu.RLock()
+	defer p.localMu.RUnlock()
+	return len(p.grains), p.poolSize
+}
+
+// SetAvailable pre-populates placeholder entries.
+func (p *CartPool) SetAvailable(availableWithLastChangeUnix map[CartId]int64) {
+	p.localMu.Lock()
+	defer p.localMu.Unlock()
+	for id := range availableWithLastChangeUnix {
+		k := uint64(id)
+		if _, ok := p.grains[k]; !ok {
+			p.grains[k] = nil
+			p.expiry = append(p.expiry, Ttl{Expires: time.Now().Add(p.ttl)})
+		}
+	}
+	p.statsUpdate()
+}
+
+// Purge removes expired grains and broadcasts expiry announcements so that
+// other hosts drop stale ownership hints.
+func (p *CartPool) Purge() {
+	now := time.Now()
+	keepChanged := now.Add(-p.ttl).Unix()
+	var expired []CartId
+
+	p.localMu.Lock()
+	for i := 0; i < len(p.expiry); {
+		entry := p.expiry[i]
+		if entry.Grain == nil {
+			i++
+			continue
+		}
+		if entry.Expires.After(now) {
+			break
+		}
+		if entry.Grain.GetLastChange() > keepChanged {
+			// Recently mutated: move to back.
+			p.expiry = append(p.expiry[:i], p.expiry[i+1:]...)
+			p.expiry = append(p.expiry, entry)
+			continue
+		}
+		id := entry.Grain.GetId()
+		delete(p.grains, uint64(id))
+		expired = append(expired, id)
+		if i < len(p.expiry)-1 {
+			p.expiry = append(p.expiry[:i], p.expiry[i+1:]...)
 		} else {
+			p.expiry = p.expiry[:i]
+		}
+	}
+	p.localMu.Unlock()
+
+	if len(expired) > 0 {
+		p.statsUpdate()
+		go p.broadcastExpiry(expired)
+	}
+}
+
+// RefreshExpiry updates the TTL entry for a given grain.
+func (p *CartPool) RefreshExpiry(id CartId) {
+	p.localMu.Lock()
+	defer p.localMu.Unlock()
+	for i := range p.expiry {
+		g := p.expiry[i].Grain
+		if g != nil && g.Id == id {
+			p.expiry[i].Expires = time.Now().Add(p.ttl)
+			return
+		}
+	}
+	// If no entry existed, append one (safeguard for newly spawned grains).
+	p.expiry = append(p.expiry, Ttl{Expires: time.Now().Add(p.ttl), Grain: p.grains[uint64(id)]})
+}
+
+// DebugGrainCount returns the number of locally resident grains.
+func (p *CartPool) DebugGrainCount() int {
+	p.localMu.RLock()
+	defer p.localMu.RUnlock()
+	return len(p.grains)
+}
+
+// LocalCartIDs returns the currently owned cart ids (for control-plane RPCs).
+func (p *CartPool) LocalCartIDs() []uint64 {
+	p.localMu.RLock()
+	defer p.localMu.RUnlock()
+	ids := make([]uint64, 0, len(p.grains))
+	for _, g := range p.grains {
+		if g == nil {
+			continue
+		}
+		ids = append(ids, uint64(g.GetId()))
+	}
+	return ids
+}
+
+// SnapshotGrains returns a copy of the currently resident grains keyed by id.
+func (p *CartPool) SnapshotGrains() map[CartId]*CartGrain {
+	p.localMu.RLock()
+	defer p.localMu.RUnlock()
+	out := make(map[CartId]*CartGrain, len(p.grains))
+	for _, g := range p.grains {
+		if g != nil {
+			out[g.GetId()] = g
+		}
+	}
+	return out
+}
+
+func (p *CartPool) removeLocalGrain(id CartId) {
+	p.localMu.Lock()
+	delete(p.grains, uint64(id))
+	for i := range p.expiry {
+		if p.expiry[i].Grain != nil && p.expiry[i].Grain.GetId() == id {
+			p.expiry = append(p.expiry[:i], p.expiry[i+1:]...)
 			break
 		}
 	}
+	p.localMu.Unlock()
+	p.statsUpdate()
 }
 
-func (p *GrainLocalPool) GetGrains() map[CartId]*CartGrain {
-	return p.grains
-}
-
-func (p *GrainLocalPool) GetGrain(id CartId) (*CartGrain, error) {
-	var err error
-	// p.mu.RLock()
-	// defer p.mu.RUnlock()
-	grain, ok := p.grains[id]
+func (p *CartPool) getLocalGrain(id CartId) (*CartGrain, error) {
+	key := uint64(id)
 	grainLookups.Inc()
+
+	p.localMu.RLock()
+	grain, ok := p.grains[key]
+	p.localMu.RUnlock()
+	if grain != nil && ok {
+		return grain, nil
+	}
+
+	p.localMu.Lock()
+	defer p.localMu.Unlock()
+	grain, ok = p.grains[key]
 	if grain == nil || !ok {
-		if len(p.grains) >= p.PoolSize {
-			if p.expiry[0].Expires.Before(time.Now()) {
-				delete(p.grains, p.expiry[0].Grain.GetId())
+		if len(p.grains) >= p.poolSize && len(p.expiry) > 0 {
+			if p.expiry[0].Expires.Before(time.Now()) && p.expiry[0].Grain != nil {
+				oldID := p.expiry[0].Grain.GetId()
+				delete(p.grains, uint64(oldID))
 				p.expiry = p.expiry[1:]
+				go p.broadcastExpiry([]CartId{oldID})
 			} else {
 				return nil, fmt.Errorf("pool is full")
 			}
 		}
-		grain, err = p.spawn(id)
-		p.mu.Lock()
-		p.grains[id] = grain
-		p.mu.Unlock()
+		spawned, err := p.spawn(id)
+		if err != nil {
+			return nil, err
+		}
+		p.grains[key] = spawned
+		p.expiry = append(p.expiry, Ttl{Expires: time.Now().Add(p.ttl), Grain: spawned})
+		grain = spawned
 	}
-	go func() {
-		l := float64(len(p.grains))
-		ps := float64(p.PoolSize)
-		poolUsage.Set(l / ps)
-		poolGrains.Set(l)
-		poolSize.Set(ps)
-	}()
-	return grain, err
+	go p.statsUpdate()
+	return grain, nil
 }
 
-func (p *GrainLocalPool) Process(id CartId, messages ...Message) (*FrameWithPayload, error) {
-	grain, err := p.GetGrain(id)
-	var result *FrameWithPayload
-	if err == nil && grain != nil {
-		for _, message := range messages {
-			result, err = grain.HandleMessage(&message, false)
+// ---------------------------------------------------------------------------
+// Cluster ownership and coordination
+// ---------------------------------------------------------------------------
+
+func (p *CartPool) TakeOwnership(id CartId) {
+	p.broadcastOwnership([]CartId{id})
+}
+
+func (p *CartPool) AddRemote(host string) {
+	if host == "" || host == p.hostname {
+		return
+	}
+
+	p.remoteMu.Lock()
+	if _, exists := p.remoteHosts[host]; exists {
+		p.remoteMu.Unlock()
+		return
+	}
+	p.remoteMu.Unlock()
+
+	target := fmt.Sprintf("%s:1337", host)
+	dialCtx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
+	conn, err := grpc.DialContext(dialCtx, target, grpc.WithTransportCredentials(insecure.NewCredentials()), grpc.WithBlock())
+	cancel()
+	if err != nil {
+		log.Printf("AddRemote: dial %s failed: %v", target, err)
+		return
+	}
+
+	controlClient := messages.NewControlPlaneClient(conn)
+	for retries := 0; retries < 3; retries++ {
+		ctx, pingCancel := context.WithTimeout(context.Background(), time.Second)
+		_, pingErr := controlClient.Ping(ctx, &messages.Empty{})
+		pingCancel()
+		if pingErr == nil {
+			break
+		}
+		if retries == 2 {
+			log.Printf("AddRemote: ping %s failed after retries: %v", host, pingErr)
+			conn.Close()
+			return
+		}
+		time.Sleep(200 * time.Millisecond)
+	}
+
+	transport := &http.Transport{
+		MaxIdleConns:        100,
+		MaxIdleConnsPerHost: 100,
+		IdleConnTimeout:     120 * time.Second,
+	}
+	client := &http.Client{Transport: transport, Timeout: 10 * time.Second}
+
+	remote := &RemoteHostGRPC{
+		Host:          host,
+		HTTPBase:      fmt.Sprintf("http://%s:8080/cart", host),
+		Conn:          conn,
+		Transport:     transport,
+		Client:        client,
+		ControlClient: controlClient,
+	}
+
+	p.remoteMu.Lock()
+	p.remoteHosts[host] = remote
+	p.remoteMu.Unlock()
+	connectedRemotes.Set(float64(p.RemoteCount()))
+
+	log.Printf("Connected to remote host %s", host)
+
+	go p.pingLoop(remote)
+	go p.initializeRemote(remote)
+	go p.Negotiate()
+}
+
+func (p *CartPool) initializeRemote(remote *RemoteHostGRPC) {
+	ctx, cancel := context.WithTimeout(context.Background(), 3*time.Second)
+	defer cancel()
+	reply, err := remote.ControlClient.GetCartIds(ctx, &messages.Empty{})
+	if err != nil {
+		log.Printf("Init remote %s: GetCartIds error: %v", remote.Host, err)
+		return
+	}
+	count := 0
+	p.remoteMu.Lock()
+	for _, cid := range reply.CartIds {
+		id := CartId(cid)
+		if _, exists := p.remoteOwners[id]; !exists {
+			p.remoteOwners[id] = remote
+		}
+		count++
+	}
+	p.remoteMu.Unlock()
+	log.Printf("Remote %s reported %d remote-owned carts", remote.Host, count)
+}
+
+func (p *CartPool) RemoveHost(host string) {
+	p.remoteMu.Lock()
+	remote, exists := p.remoteHosts[host]
+	if exists {
+		delete(p.remoteHosts, host)
+	}
+	for id, owner := range p.remoteOwners {
+		if owner.Host == host {
+			delete(p.remoteOwners, id)
 		}
 	}
-	return result, err
+	p.remoteMu.Unlock()
+
+	if exists {
+		remote.Conn.Close()
+	}
+	connectedRemotes.Set(float64(p.RemoteCount()))
 }
 
-func (p *GrainLocalPool) Get(id CartId) (*FrameWithPayload, error) {
-	grain, err := p.GetGrain(id)
-	if err != nil {
-		return nil, err
-	}
-	data, err := json.Marshal(grain)
-	if err != nil {
-		return nil, err
-	}
-	ret := MakeFrameWithPayload(0, 200, data)
-	return &ret, nil
+func (p *CartPool) RemoteCount() int {
+	p.remoteMu.RLock()
+	defer p.remoteMu.RUnlock()
+	return len(p.remoteHosts)
+}
+
+// RemoteHostNames returns a snapshot of connected remote host identifiers.
+func (p *CartPool) RemoteHostNames() []string {
+	p.remoteMu.RLock()
+	defer p.remoteMu.RUnlock()
+	hosts := make([]string, 0, len(p.remoteHosts))
+	for host := range p.remoteHosts {
+		hosts = append(hosts, host)
+	}
+	return hosts
+}
+
+func (p *CartPool) IsKnown(host string) bool {
+	if host == p.hostname {
+		return true
+	}
+	p.remoteMu.RLock()
+	defer p.remoteMu.RUnlock()
+	_, ok := p.remoteHosts[host]
+	return ok
+}
+
+func (p *CartPool) pingLoop(remote *RemoteHostGRPC) {
+	ticker := time.NewTicker(3 * time.Second)
+	defer ticker.Stop()
+	for range ticker.C {
+		ctx, cancel := context.WithTimeout(context.Background(), time.Second)
+		_, err := remote.ControlClient.Ping(ctx, &messages.Empty{})
+		cancel()
+		if err != nil {
+			remote.MissedPings++
+			log.Printf("Ping %s failed (%d)", remote.Host, remote.MissedPings)
+			if !remote.IsHealthy() {
+				log.Printf("Remote %s unhealthy, removing", remote.Host)
+				p.RemoveHost(remote.Host)
+				return
+			}
+			continue
+		}
+		remote.MissedPings = 0
+	}
+}
+
+func (p *CartPool) IsHealthy() bool {
+	p.remoteMu.RLock()
+	defer p.remoteMu.RUnlock()
+	for _, r := range p.remoteHosts {
+		if !r.IsHealthy() {
+			return false
+		}
+	}
+	return true
+}
+
+func (p *CartPool) Negotiate() {
+	negotiationCount.Inc()
+
+	p.remoteMu.RLock()
+	hosts := make([]string, 0, len(p.remoteHosts)+1)
+	hosts = append(hosts, p.hostname)
+	remotes := make([]*RemoteHostGRPC, 0, len(p.remoteHosts))
+	for h, r := range p.remoteHosts {
+		hosts = append(hosts, h)
+		remotes = append(remotes, r)
+	}
+	p.remoteMu.RUnlock()
+
+	for _, r := range remotes {
+		ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
+		reply, err := r.ControlClient.Negotiate(ctx, &messages.NegotiateRequest{KnownHosts: hosts})
+		cancel()
+		if err != nil {
+			log.Printf("Negotiate with %s failed: %v", r.Host, err)
+			continue
+		}
+		for _, h := range reply.Hosts {
+			if !p.IsKnown(h) {
+				p.AddRemote(h)
+			}
+		}
+	}
+}
+
+func (p *CartPool) broadcastOwnership(ids []CartId) {
+	if len(ids) == 0 {
+		return
+	}
+	uids := make([]uint64, len(ids))
+	for i, id := range ids {
+		uids[i] = uint64(id)
+	}
+
+	p.remoteMu.RLock()
+	remotes := make([]*RemoteHostGRPC, 0, len(p.remoteHosts))
+	for _, r := range p.remoteHosts {
+		if r.IsHealthy() {
+			remotes = append(remotes, r)
+		}
+	}
+	p.remoteMu.RUnlock()
+
+	for _, remote := range remotes {
+		go func(rh *RemoteHostGRPC) {
+			_, err := rh.ControlClient.AnnounceOwnership(context.Background(), &messages.OwnershipAnnounce{
+				Host:    p.hostname,
+				CartIds: uids,
+			})
+			if err != nil {
+				log.Printf("ownership announce to %s failed: %v", rh.Host, err)
+			}
+		}(remote)
+	}
+}
+
+func (p *CartPool) broadcastExpiry(ids []CartId) {
+	if len(ids) == 0 {
+		return
+	}
+	uids := make([]uint64, len(ids))
+	for i, id := range ids {
+		uids[i] = uint64(id)
+	}
+
+	p.remoteMu.RLock()
+	remotes := make([]*RemoteHostGRPC, 0, len(p.remoteHosts))
+	for _, r := range p.remoteHosts {
+		if r.IsHealthy() {
+			remotes = append(remotes, r)
+		}
+	}
+	p.remoteMu.RUnlock()
+
+	for _, remote := range remotes {
+		go func(rh *RemoteHostGRPC) {
+			_, err := rh.ControlClient.AnnounceExpiry(context.Background(), &messages.ExpiryAnnounce{
+				Host:    p.hostname,
+				CartIds: uids,
+			})
+			if err != nil {
+				log.Printf("expiry announce to %s failed: %v", rh.Host, err)
+			}
+		}(remote)
+	}
+}
+
+func (p *CartPool) AdoptRemoteOwnership(host string, ids []string) {
+	if host == "" || host == p.hostname {
+		return
+	}
+	remoteHost, ok := p.remoteHosts[host]
+	if !ok {
+		log.Printf("AdoptRemoteOwnership: unknown host %s", host)
+	}
+	p.remoteMu.Lock()
+	defer p.remoteMu.Unlock()
+	for _, s := range ids {
+		if s == "" {
+			continue
+		}
+		parsed, ok := ParseCartId(s)
+		if !ok {
+			continue
+		}
+		if existing, ok := p.remoteOwners[parsed]; ok && existing != remoteHost {
+			continue
+		}
+		p.localMu.RLock()
+		_, localHas := p.grains[uint64(parsed)]
+		p.localMu.RUnlock()
+		if localHas {
+			continue
+		}
+		p.remoteOwners[parsed] = remoteHost
+	}
+}
+
+func (p *CartPool) HandleRemoteExpiry(host string, ids []uint64) {
+	if host == "" || host == p.hostname {
+		return
+	}
+	p.remoteMu.Lock()
+	defer p.remoteMu.Unlock()
+	for _, raw := range ids {
+		id := CartId(raw)
+		if owner, ok := p.remoteOwners[id]; ok && owner.Host == host {
+			delete(p.remoteOwners, id)
+		}
+	}
+}
+
+func (p *CartPool) getOrClaimGrain(id CartId) (*CartGrain, error) {
+	p.localMu.RLock()
+	grain, exists := p.grains[uint64(id)]
+	p.localMu.RUnlock()
+	if exists && grain != nil {
+		return grain, nil
+	}
+
+	p.remoteMu.RLock()
+	remoteHost, found := p.remoteOwners[id]
+	p.remoteMu.RUnlock()
+	if found && remoteHost != nil && remoteHost.Host != "" {
+		return nil, ErrNotOwner
+	}
+
+	grain, err := p.getLocalGrain(id)
+	if err != nil {
+		return nil, err
+	}
+	go p.broadcastOwnership([]CartId{id})
+	return grain, nil
+}
+
+// ErrNotOwner is returned when a cart belongs to another host.
+var ErrNotOwner = fmt.Errorf("not owner")
+
+// Apply applies a mutation to a grain.
+func (p *CartPool) Apply(id CartId, mutation interface{}) (*CartGrain, error) {
+	grain, err := p.getOrClaimGrain(id)
+	if err != nil {
+		return nil, err
+	}
+	start := time.Now()
+	result, applyErr := grain.Apply(mutation, false)
+	mutationType := "unknown"
+	if mutation != nil {
+		if t := reflect.TypeOf(mutation); t != nil {
+			if t.Kind() == reflect.Ptr {
+				t = t.Elem()
+			}
+			if t.Name() != "" {
+				mutationType = t.Name()
+			}
+		}
+	}
+	cartMutationLatencySeconds.WithLabelValues(mutationType).Observe(time.Since(start).Seconds())
+
+	if applyErr == nil && result != nil {
+		cartMutationsTotal.Inc()
+		p.RefreshExpiry(id)
+		cartActiveGrains.Set(float64(p.DebugGrainCount()))
+	} else if applyErr != nil {
+		cartMutationFailuresTotal.Inc()
+	}
+
+	return result, applyErr
+}
+
+// Get returns the current state of a grain.
+func (p *CartPool) Get(id CartId) (*CartGrain, error) {
+	grain, err := p.getOrClaimGrain(id)
+	if err != nil {
+		return nil, err
+	}
+	return grain.GetCurrentState()
+}
+
+// OwnerHost reports the remote owner (if any) for the supplied cart id.
+func (p *CartPool) OwnerHost(id CartId) (Host, bool) {
+	p.remoteMu.RLock()
+	defer p.remoteMu.RUnlock()
+	owner, ok := p.remoteOwners[id]
+	return owner, ok
+}
+
+// Hostname returns the local hostname (pod IP).
+func (p *CartPool) Hostname() string {
+	return p.hostname
+}
+
+// Close notifies remotes that this host is shutting down.
+func (p *CartPool) Close() {
+	p.remoteMu.Lock()
+	defer p.remoteMu.Unlock()
+	for _, r := range p.remoteHosts {
+		go func(rh *RemoteHostGRPC) {
+			_, err := rh.ControlClient.Closing(context.Background(), &messages.ClosingNotice{Host: p.hostname})
+			if err != nil {
+				log.Printf("Close notify to %s failed: %v", rh.Host, err)
+			}
+		}(r)
+	}
+	if p.purgeTicker != nil {
+		p.purgeTicker.Stop()
+	}
 }

grpc_integration_test.go

@@ -1,135 +0,0 @@
-package main
-
-import (
-	"bytes"
-	"context"
-	"encoding/json"
-	"fmt"
-	"testing"
-	"time"
-
-	messages "git.tornberg.me/go-cart-actor/proto"
-	"google.golang.org/grpc"
-)
-
-// TestCartActorMutationAndState validates end-to-end gRPC mutation + state retrieval
-// against a locally started gRPC server (single-node scenario).
-// This test uses AddItemType directly to avoid hitting external product
-// fetching logic (FetchItem) which would require network I/O.
-func TestCartActorMutationAndState(t *testing.T) {
-	// Setup local grain pool + synced pool (no discovery, single host)
-	pool := NewGrainLocalPool(1024, time.Minute, spawn)
-	synced, err := NewSyncedPool(pool, "127.0.0.1", nil)
-	if err != nil {
-		t.Fatalf("NewSyncedPool error: %v", err)
-	}
-
-	// Start gRPC server (CartActor + ControlPlane) on :1337
-	grpcSrv, err := StartGRPCServer(":1337", pool, synced)
-	if err != nil {
-		t.Fatalf("StartGRPCServer error: %v", err)
-	}
-	defer grpcSrv.GracefulStop()
-
-	// Dial the local server
-	ctx, cancel := context.WithTimeout(context.Background(), 3*time.Second)
-	defer cancel()
-	conn, err := grpc.DialContext(ctx, "127.0.0.1:1337",
-		grpc.WithInsecure(),
-		grpc.WithBlock(),
-	)
-	if err != nil {
-		t.Fatalf("grpc.Dial error: %v", err)
-	}
-	defer conn.Close()
-
-	cartClient := messages.NewCartActorClient(conn)
-
-	// Create a short cart id (<=16 chars so it fits into the fixed CartId 16-byte array cleanly)
-	cartID := fmt.Sprintf("cart-%d", time.Now().UnixNano())
-
-	// Build an AddItem payload (bypasses FetchItem to keep test deterministic)
-	addItem := &messages.AddItem{
-		ItemId:   1,
-		Quantity: 1,
-		Price:    1000,
-		OrgPrice: 1000,
-		Sku:      "test-sku",
-		Name:     "Test SKU",
-		Image:    "/img.png",
-		Stock:    2, // InStock
-		Tax:      2500,
-		Country:  "se",
-	}
-
-	// Marshal underlying mutation payload using the existing handler code path
-	handler, ok := Handlers[AddItemType]
-	if !ok {
-		t.Fatalf("Handler for AddItemType missing")
-	}
-	payloadData, err := getSerializedPayload(handler, AddItemType, addItem)
-	if err != nil {
-		t.Fatalf("serialize add item: %v", err)
-	}
-
-	// Issue Mutate RPC
-	mutResp, err := cartClient.Mutate(context.Background(), &messages.MutationRequest{
-		CartId:          cartID,
-		Type:            messages.MutationType(AddItemType),
-		Payload:         payloadData,
-		ClientTimestamp: time.Now().Unix(),
-	})
-	if err != nil {
-		t.Fatalf("Mutate RPC error: %v", err)
-	}
-	if mutResp.StatusCode != 200 {
-		t.Fatalf("Mutate returned non-200 status: %d payload=%s", mutResp.StatusCode, string(mutResp.Payload))
-	}
-
-	// Decode cart state JSON and validate
-	state := &CartGrain{}
-	if err := json.Unmarshal(mutResp.Payload, state); err != nil {
-		t.Fatalf("Unmarshal mutate cart state: %v\nPayload: %s", err, string(mutResp.Payload))
-	}
-	if len(state.Items) != 1 {
-		t.Fatalf("Expected 1 item after mutation, got %d", len(state.Items))
-	}
-	if state.Items[0].Sku != "test-sku" {
-		t.Fatalf("Unexpected item SKU: %s", state.Items[0].Sku)
-	}
-
-	// Issue GetState RPC
-	getResp, err := cartClient.GetState(context.Background(), &messages.StateRequest{
-		CartId: cartID,
-	})
-	if err != nil {
-		t.Fatalf("GetState RPC error: %v", err)
-	}
-	if getResp.StatusCode != 200 {
-		t.Fatalf("GetState returned non-200 status: %d payload=%s", getResp.StatusCode, string(getResp.Payload))
-	}
-
-	state2 := &CartGrain{}
-	if err := json.Unmarshal(getResp.Payload, state2); err != nil {
-		t.Fatalf("Unmarshal get state: %v", err)
-	}
-	if len(state2.Items) != 1 {
-		t.Fatalf("Expected 1 item in GetState, got %d", len(state2.Items))
-	}
-	if state2.Items[0].Sku != "test-sku" {
-		t.Fatalf("Unexpected SKU in GetState: %s", state2.Items[0].Sku)
-	}
-}
-
-// getSerializedPayload serializes a mutation proto using the registered handler.
-func getSerializedPayload(handler MessageHandler, msgType uint16, content interface{}) ([]byte, error) {
-	msg := &Message{
-		Type:    msgType,
-		Content: content,
-	}
-	var buf bytes.Buffer
-	if err := handler.Write(msg, &buf); err != nil {
-		return nil, err
-	}
-	return buf.Bytes(), nil
-}

grpc_server.go

@@ -2,378 +2,120 @@ package main
 
 import (
 	"context"
-	"errors"
 	"fmt"
 	"log"
 	"net"
 	"time"
 
-	proto "git.tornberg.me/go-cart-actor/proto" // underlying generated package name is 'messages'
-	"github.com/prometheus/client_golang/prometheus"
-	"github.com/prometheus/client_golang/prometheus/promauto"
+	messages "git.tornberg.me/go-cart-actor/proto"
 	"google.golang.org/grpc"
-	"google.golang.org/grpc/codes"
-	"google.golang.org/grpc/status"
+	"google.golang.org/grpc/reflection"
 )
 
-// -----------------------------------------------------------------------------
-// Metrics
-// -----------------------------------------------------------------------------
+// cartActorGRPCServer implements the ControlPlane gRPC services.
+// It delegates cart operations to a grain pool and cluster operations to a synced pool.
+type cartActorGRPCServer struct {
+	messages.UnimplementedControlPlaneServer
 
-var (
-	grpcMutateDuration = promauto.NewHistogram(prometheus.HistogramOpts{
-		Name:    "cart_grpc_mutate_duration_seconds",
-		Help:    "Duration of CartActor.Mutate RPCs",
-		Buckets: prometheus.DefBuckets,
-	})
-	grpcMutateErrors = promauto.NewCounter(prometheus.CounterOpts{
-		Name: "cart_grpc_mutate_errors_total",
-		Help: "Total number of failed CartActor.Mutate RPCs",
-	})
-	grpcStateDuration = promauto.NewHistogram(prometheus.HistogramOpts{
-		Name:    "cart_grpc_get_state_duration_seconds",
-		Help:    "Duration of CartActor.GetState RPCs",
-		Buckets: prometheus.DefBuckets,
-	})
-	grpcControlDuration = promauto.NewHistogram(prometheus.HistogramOpts{
-		Name:    "cart_grpc_control_duration_seconds",
-		Help:    "Duration of ControlPlane RPCs",
-		Buckets: prometheus.DefBuckets,
-	})
-	grpcControlErrors = promauto.NewCounter(prometheus.CounterOpts{
-		Name: "cart_grpc_control_errors_total",
-		Help: "Total number of failed ControlPlane RPCs",
-	})
-)
-
-// timeTrack wraps a closure and records duration into the supplied histogram.
-func timeTrack(hist prometheus.Observer, fn func() error) (err error) {
-	start := time.Now()
-	defer func() {
-		hist.Observe(time.Since(start).Seconds())
-	}()
-	return fn()
+	pool *CartPool
 }
 
-// -----------------------------------------------------------------------------
-// CartActor Service Implementation
-// -----------------------------------------------------------------------------
-
-type cartActorService struct {
-	proto.UnimplementedCartActorServer
-	pool GrainPool
-}
-
-func newCartActorService(pool GrainPool) *cartActorService {
-	return &cartActorService{pool: pool}
-}
-
-func (s *cartActorService) Mutate(ctx context.Context, req *proto.MutationRequest) (*proto.MutationReply, error) {
-	var reply *proto.MutationReply
-	err := timeTrack(grpcMutateDuration, func() error {
-		if req == nil {
-			return status.Error(codes.InvalidArgument, "request is nil")
-		}
-		if req.CartId == "" {
-			return status.Error(codes.InvalidArgument, "cart_id is empty")
-		}
-		mt := uint16(req.Type.Number())
-		handler, ok := Handlers[mt]
-		if !ok {
-			return status.Errorf(codes.InvalidArgument, "unknown mutation type %d", mt)
-		}
-		content, err := handler.Read(req.Payload)
-		if err != nil {
-			return status.Errorf(codes.InvalidArgument, "decode payload: %v", err)
-		}
-
-		ts := req.ClientTimestamp
-		if ts == 0 {
-			ts = time.Now().Unix()
-		}
-		msg := Message{
-			Type:      mt,
-			TimeStamp: &ts,
-			Content:   content,
-		}
-
-		frame, err := s.pool.Process(ToCartId(req.CartId), msg)
-		if err != nil {
-			return err
-		}
-		reply = &proto.MutationReply{
-			StatusCode: int32(frame.StatusCode),
-			Payload:    frame.Payload,
-		}
-		return nil
-	})
-	if err != nil {
-		grpcMutateErrors.Inc()
-		return nil, err
+// NewCartActorGRPCServer creates and initializes the server.
+func NewCartActorGRPCServer(pool *CartPool) *cartActorGRPCServer {
+	return &cartActorGRPCServer{
+		pool: pool,
 	}
-	return reply, nil
 }
 
-func (s *cartActorService) GetState(ctx context.Context, req *proto.StateRequest) (*proto.StateReply, error) {
-	var reply *proto.StateReply
-	err := timeTrack(grpcStateDuration, func() error {
-		if req == nil || req.CartId == "" {
-			return status.Error(codes.InvalidArgument, "cart_id is empty")
-		}
-		frame, err := s.pool.Get(ToCartId(req.CartId))
-		if err != nil {
-			return err
-		}
-		reply = &proto.StateReply{
-			StatusCode: int32(frame.StatusCode),
-			Payload:    frame.Payload,
-		}
-		return nil
-	})
-	if err != nil {
-		return nil, err
+func (s *cartActorGRPCServer) AnnounceOwnership(ctx context.Context, req *messages.OwnershipAnnounce) (*messages.OwnerChangeAck, error) {
+	for _, cartId := range req.CartIds {
+		s.pool.removeLocalGrain(CartId(cartId))
 	}
-	return reply, nil
-}
-
-// -----------------------------------------------------------------------------
-// ControlPlane Service Implementation
-// -----------------------------------------------------------------------------
-
-// controlPlaneService directly leverages SyncedPool internals (same package).
-// NOTE: This is a transitional adapter; once the legacy frame-based code is
-// removed, related fields/methods in SyncedPool can be slimmed.
-type controlPlaneService struct {
-	proto.UnimplementedControlPlaneServer
-	pool *SyncedPool
-}
-
-func newControlPlaneService(pool *SyncedPool) *controlPlaneService {
-	return &controlPlaneService{pool: pool}
-}
-
-func (s *controlPlaneService) Ping(ctx context.Context, _ *proto.Empty) (*proto.PingReply, error) {
-	var reply *proto.PingReply
-	err := timeTrack(grpcControlDuration, func() error {
-		reply = &proto.PingReply{
-			Host:     s.pool.Hostname,
-			UnixTime: time.Now().Unix(),
-		}
-		return nil
-	})
-	if err != nil {
-		grpcControlErrors.Inc()
-		return nil, err
-	}
-	return reply, nil
-}
-
-func (s *controlPlaneService) Negotiate(ctx context.Context, req *proto.NegotiateRequest) (*proto.NegotiateReply, error) {
-	var reply *proto.NegotiateReply
-	err := timeTrack(grpcControlDuration, func() error {
-		if req == nil {
-			return status.Error(codes.InvalidArgument, "request is nil")
-		}
-		// Add unknown hosts
-		for _, host := range req.KnownHosts {
-			if host == "" || host == s.pool.Hostname {
-				continue
-			}
-			if !s.pool.IsKnown(host) {
-				go s.pool.AddRemote(host)
-			}
-		}
-		// Build healthy host list
-		hosts := make([]string, 0)
-		for _, r := range s.pool.GetHealthyRemotes() {
-			hosts = append(hosts, r.Host)
-		}
-		hosts = append(hosts, s.pool.Hostname)
-		reply = &proto.NegotiateReply{
-			Hosts: hosts,
-		}
-		return nil
-	})
-	if err != nil {
-		grpcControlErrors.Inc()
-		return nil, err
-	}
-	return reply, nil
-}
-
-func (s *controlPlaneService) GetCartIds(ctx context.Context, _ *proto.Empty) (*proto.CartIdsReply, error) {
-	var reply *proto.CartIdsReply
-	err := timeTrack(grpcControlDuration, func() error {
-		s.pool.mu.RLock()
-		defer s.pool.mu.RUnlock()
-		ids := make([]string, 0, len(s.pool.local.grains))
-		for id, g := range s.pool.local.grains {
-			if g == nil {
-				continue
-			}
-			if id.String() == "" {
-				continue
-			}
-			ids = append(ids, id.String())
-		}
-		reply = &proto.CartIdsReply{
-			CartIds: ids,
-		}
-		return nil
-	})
-	if err != nil {
-		grpcControlErrors.Inc()
-		return nil, err
-	}
-	return reply, nil
-}
-
-func (s *controlPlaneService) ConfirmOwner(ctx context.Context, req *proto.OwnerChangeRequest) (*proto.OwnerChangeAck, error) {
-	var reply *proto.OwnerChangeAck
-	err := timeTrack(grpcControlDuration, func() error {
-		if req == nil || req.CartId == "" || req.NewHost == "" {
-			return status.Error(codes.InvalidArgument, "cart_id or new_host missing")
-		}
-		id := ToCartId(req.CartId)
-		newHost := req.NewHost
-
-		// Mirror GrainOwnerChangeHandler semantics
-		log.Printf("gRPC ConfirmOwner: cart %s newHost=%s", id, newHost)
-		for _, r := range s.pool.remoteHosts {
-			if r.Host == newHost && r.IsHealthy() {
-				go s.pool.SpawnRemoteGrain(id, newHost)
-				break
-			}
-		}
-		go s.pool.AddRemote(newHost)
-
-		reply = &proto.OwnerChangeAck{
-			Accepted: true,
-			Message:  "ok",
-		}
-		return nil
-	})
-	if err != nil {
-		grpcControlErrors.Inc()
-		return nil, err
-	}
-	return reply, nil
-}
-
-func (s *controlPlaneService) Closing(ctx context.Context, notice *proto.ClosingNotice) (*proto.OwnerChangeAck, error) {
-	var reply *proto.OwnerChangeAck
-	err := timeTrack(grpcControlDuration, func() error {
-		if notice == nil || notice.Host == "" {
-			return status.Error(codes.InvalidArgument, "host missing")
-		}
-		host := notice.Host
-		s.pool.mu.RLock()
-		_, exists := s.pool.remoteHosts[host]
-		s.pool.mu.RUnlock()
-		if exists {
-			go s.pool.RemoveHost(host)
-		}
-		reply = &proto.OwnerChangeAck{
-			Accepted: true,
-			Message:  "removed",
-		}
-		return nil
-	})
-	if err != nil {
-		grpcControlErrors.Inc()
-		return nil, err
-	}
-	return reply, nil
-}
-
-// -----------------------------------------------------------------------------
-// Server Bootstrap
-// -----------------------------------------------------------------------------
-
-type GRPCServer struct {
-	server *grpc.Server
-	lis    net.Listener
-	addr   string
-}
-
-// StartGRPCServer sets up a gRPC server hosting both CartActor and ControlPlane services.
-// addr example: ":1337" (for combined) OR run two servers if you want separate ports.
-// For the migration we can host both on the same listener to reduce open ports.
-func StartGRPCServer(addr string, pool GrainPool, synced *SyncedPool, opts ...grpc.ServerOption) (*GRPCServer, error) {
-	if pool == nil {
-		return nil, errors.New("nil grain pool")
-	}
-	if synced == nil {
-		return nil, errors.New("nil synced pool")
-	}
-
-	lis, err := net.Listen("tcp", addr)
-	if err != nil {
-		return nil, fmt.Errorf("listen %s: %w", addr, err)
-	}
-
-	grpcServer := grpc.NewServer(opts...)
-	proto.RegisterCartActorServer(grpcServer, newCartActorService(pool))
-	proto.RegisterControlPlaneServer(grpcServer, newControlPlaneService(synced))
-
-	go func() {
-		log.Printf("gRPC server listening on %s", addr)
-		if serveErr := grpcServer.Serve(lis); serveErr != nil {
-			log.Printf("gRPC server stopped: %v", serveErr)
-		}
-	}()
-
-	return &GRPCServer{
-		server: grpcServer,
-		lis:    lis,
-		addr:   addr,
+	log.Printf("Ack count: %d", len(req.CartIds))
+	return &messages.OwnerChangeAck{
+		Accepted: true,
+		Message:  "ownership announced",
 	}, nil
 }
 
-// GracefulStop stops the server gracefully.
-func (s *GRPCServer) GracefulStop() {
-	if s == nil || s.server == nil {
-		return
-	}
-	s.server.GracefulStop()
+func (s *cartActorGRPCServer) AnnounceExpiry(ctx context.Context, req *messages.ExpiryAnnounce) (*messages.OwnerChangeAck, error) {
+	s.pool.HandleRemoteExpiry(req.GetHost(), req.GetCartIds())
+	return &messages.OwnerChangeAck{
+		Accepted: true,
+		Message:  "expiry acknowledged",
+	}, nil
 }
 
-// Addr returns the bound address.
-func (s *GRPCServer) Addr() string {
-	if s == nil {
-		return ""
-	}
-	return s.addr
+// ControlPlane: Ping
+func (s *cartActorGRPCServer) Ping(ctx context.Context, _ *messages.Empty) (*messages.PingReply, error) {
+	// Expose cart owner cookie (first-touch owner = this host) for HTTP gateways translating gRPC metadata.
+	// Gateways that propagate Set-Cookie can help establish sticky sessions at the edge.
+	//_ = grpc.SendHeader(ctx, metadata.Pairs("set-cookie", fmt.Sprintf("cartowner=%s; Path=/; HttpOnly", s.syncedPool.Hostname())))
+	return &messages.PingReply{
+		Host:     s.pool.Hostname(),
+		UnixTime: time.Now().Unix(),
+	}, nil
 }
 
-// -----------------------------------------------------------------------------
-// Client Dial Helpers (used later by refactored remote grain + control plane)
-// -----------------------------------------------------------------------------
-
-// DialRemote establishes (or reuses externally) a gRPC client connection.
-func DialRemote(ctx context.Context, target string, opts ...grpc.DialOption) (*grpc.ClientConn, error) {
-	dialOpts := []grpc.DialOption{
-		grpc.WithInsecure(), // NOTE: Intentional for initial migration; replace with TLS / mTLS later.
-		grpc.WithBlock(),
+// ControlPlane: Negotiate (merge host views)
+func (s *cartActorGRPCServer) Negotiate(ctx context.Context, req *messages.NegotiateRequest) (*messages.NegotiateReply, error) {
+	hostSet := make(map[string]struct{})
+	// Caller view
+	for _, h := range req.GetKnownHosts() {
+		if h != "" {
+			hostSet[h] = struct{}{}
+		}
 	}
-	dialOpts = append(dialOpts, opts...)
-	ctxDial, cancel := context.WithTimeout(ctx, 5*time.Second)
-	defer cancel()
-	conn, err := grpc.DialContext(ctxDial, target, dialOpts...)
+	// This host
+	hostSet[s.pool.Hostname()] = struct{}{}
+	// Known remotes
+	for _, h := range s.pool.RemoteHostNames() {
+		hostSet[h] = struct{}{}
+	}
+
+	out := make([]string, 0, len(hostSet))
+	for h := range hostSet {
+		out = append(out, h)
+	}
+	return &messages.NegotiateReply{Hosts: out}, nil
+}
+
+// ControlPlane: GetCartIds (locally owned carts only)
+func (s *cartActorGRPCServer) GetCartIds(ctx context.Context, _ *messages.Empty) (*messages.CartIdsReply, error) {
+	return &messages.CartIdsReply{CartIds: s.pool.LocalCartIDs()}, nil
+}
+
+// ControlPlane: Closing (peer shutdown notification)
+func (s *cartActorGRPCServer) Closing(ctx context.Context, req *messages.ClosingNotice) (*messages.OwnerChangeAck, error) {
+	if req.GetHost() != "" {
+		s.pool.RemoveHost(req.GetHost())
+	}
+	return &messages.OwnerChangeAck{
+		Accepted: true,
+		Message:  "removed host",
+	}, nil
+}
+
+// StartGRPCServer configures and starts the unified gRPC server on the given address.
+// It registers both the CartActor and ControlPlane services.
+func StartGRPCServer(addr string, pool *CartPool) (*grpc.Server, error) {
+	lis, err := net.Listen("tcp", addr)
 	if err != nil {
-		return nil, err
+		return nil, fmt.Errorf("failed to listen: %w", err)
 	}
-	return conn, nil
-}
 
-// -----------------------------------------------------------------------------
-// Utility for converting internal errors to gRPC status (if needed later).
-// -----------------------------------------------------------------------------
+	grpcServer := grpc.NewServer()
+	server := NewCartActorGRPCServer(pool)
 
-func grpcError(err error) error {
-	if err == nil {
-		return nil
-	}
-	// Extend mapping if we add richer error types.
-	return status.Error(codes.Internal, err.Error())
+	messages.RegisterControlPlaneServer(grpcServer, server)
+	reflection.Register(grpcServer)
+
+	log.Printf("gRPC server listening on %s", addr)
+	go func() {
+		if err := grpcServer.Serve(lis); err != nil {
+			log.Fatalf("failed to serve gRPC: %v", err)
+		}
+	}()
+
+	return grpcServer, nil
 }

k6/README.md

@@ -0,0 +1,174 @@
+# k6 Load Tests for Cart API
+
+This directory contains a k6 script (`cart_load_test.js`) to stress and observe the cart actor HTTP API.
+
+## Contents
+
+- `cart_load_test.js` – primary k6 scenario script
+- `README.md` – this file
+
+## Prerequisites
+
+- Node not required (k6 runs standalone)
+- k6 installed (>= v0.43 recommended)
+- Prometheus + Grafana (optional) if you want to correlate with the dashboard you generated
+- A running cart service exposing HTTP endpoints at (default) `http://localhost:8080/cart`
+
+## Endpoints Exercised
+
+The script exercises (per iteration):
+
+1. `GET /cart/` – ensure / fetch cart state (creates cart if missing; sets `cartid` & `cartowner` cookies)
+2. `POST /cart/` – add item mutation (random SKU & quantity)
+3. `GET /cart/` – fetch after mutations
+4. `GET /cart/checkout` – occasionally (~2% of iterations) to simulate checkout start
+
+You can extend it easily to hit deliveries, quantity changes, or removal endpoints.
+
+## Environment Variables
+
+| Variable        | Purpose                                      | Default                 |
+|-----------------|----------------------------------------------|-------------------------|
+| `BASE_URL`      | Base URL root (either host or host/cart)     | `http://localhost:8080/cart` |
+| `VUS`           | VUs for steady_mutations scenario            | `20`                    |
+| `DURATION`      | Duration for steady_mutations scenario       | `5m`                    |
+| `RAMP_TARGET`   | Peak VUs for ramp_up scenario                 | `50`                    |
+
+You can also disable one scenario by editing `options.scenarios` inside the script.
+
+Example run:
+
+```bash
+k6 run \
+  -e BASE_URL=https://cart.prod.example.com/cart \
+  -e VUS=40 \
+  -e DURATION=10m \
+  -e RAMP_TARGET=120 \
+  k6/cart_load_test.js
+```
+
+## Metrics (Custom)
+
+The script defines additional k6 metrics:
+
+- `cart_add_item_duration` (Trend) – latency of POST add item
+- `cart_fetch_duration` (Trend) – latency of GET cart state
+- `cart_checkout_duration` (Trend) – latency of checkout
+- `cart_items_added` (Counter) – successful add item operations
+- `cart_checkout_calls` (Counter) – successful checkout calls
+
+Thresholds (in `options.thresholds`) enforce basic SLO:
+- Mutation failure rate < 2%
+- p90 mutation latency < 800 ms
+- p99 overall HTTP latency < 1500 ms
+
+Adjust thresholds to your environment if they trigger prematurely.
+
+## Cookies & Stickiness
+
+The script preserves:
+- `cartid` – cart identity (server sets expiry separately)
+- `cartowner` – owning host for sticky routing
+
+If your load balancer or ingress enforces affinity based on these cookies, traffic will naturally concentrate on the originally claimed host for each cart under test.
+
+## SKU Set
+
+SKUs used (randomly selected each mutation):
+
+```
+778290 778345 778317 778277 778267 778376 778244 778384
+778365 778377 778255 778286 778246 778270 778266 778285
+778329 778425 778407 778418 778430 778469 778358 778351
+778319 778307 778278 778251 778253 778261 778263 778273
+778281 778294 778297 778302
+```
+
+To add/remove SKUs, edit the `SKUS` array. Keeping it non-empty and moderately sized helps randomization.
+
+## Extending the Script
+
+### Add Quantity Change
+
+```js
+function changeQuantity(itemId, newQty) {
+  const payload = JSON.stringify({ Id: itemId, Qty: newQty });
+  http.put(baseUrl() + '/', payload, { headers: headers() });
+}
+```
+
+### Remove Item
+
+```js
+function removeItem(itemId) {
+  http.del(baseUrl() + '/' + itemId, null, { headers: headers() });
+}
+```
+
+### Add Delivery
+
+```js
+function addDelivery(itemIds) {
+  const payload = JSON.stringify({ provider: "POSTNORD", items: itemIds });
+  http.post(baseUrl() + '/delivery', payload, { headers: headers() });
+}
+```
+
+You can integrate these into the iteration loop with probabilities.
+
+## Output Summary
+
+`handleSummary` outputs a JSON summary to stdout:
+- Average & p95 mutation latencies (if present)
+- Fetch p95
+- Checkout count
+- Check statuses
+
+Redirect or parse that output for CI pipelines.
+
+## Running in CI
+
+Use shorter durations (e.g. `DURATION=2m VUS=10`) to keep builds fast. Fail build on threshold breaches:
+
+```bash
+k6 run -e BASE_URL=$TARGET -e VUS=10 -e DURATION=2m k6/cart_load_test.js || exit 1
+```
+
+## Correlating with Prometheus / Grafana
+
+During load, observe:
+- `cart_mutations_total` growth and latency histograms
+- Event log write rate (`cart_event_log_appends_total`)
+- Pool usage (`cart_grain_pool_usage`) and spawn rate (`cart_grain_spawned_total`)
+- Failure counters (`cart_mutation_failures_total`) ensure they remain low
+
+If mutation latency spikes without high error rate, inspect external dependencies (e.g., product fetcher or Klarna endpoints).
+
+## Common Tuning Tips
+
+| Symptom                             | Potential Adjustment                              |
+|------------------------------------|---------------------------------------------------|
+| High latency p99                   | Increase CPU/memory, optimize mutation handlers   |
+| Pool at capacity                   | Raise pool size argument or TTL                   |
+| Frequent cart eviction mid-test    | Confirm TTL is sliding (now 2h on mutation)       |
+| High replay duration               | Consider snapshot + truncate event logs           |
+| Uneven host load                   | Verify `cartowner` cookie is respected upstream   |
+
+## Safety / Load Guardrails
+
+- Start with low VUs (5–10) and short duration.
+- Scale incrementally to find saturation points.
+- If using production endpoints, coordinate off-peak runs.
+
+## License / Attribution
+
+This test script is tailored for your internal cart actor system; adapt freely. k6 is open-source (AGPL v3). Ensure compliance if redistributing.
+
+---
+
+Feel free to request:
+- A variant script for spike tests
+- WebSocket / long poll integration (if added later)
+- Synthetic error injection harness
+
+Happy load testing!

k6/cart_load_test.js

@@ -0,0 +1,248 @@
+import http from "k6/http";
+import { check, sleep, group } from "k6";
+import { Counter, Trend } from "k6/metrics";
+
+// ---------------- Configuration ----------------
+export const options = {
+    // Adjust vus/duration for your environment
+    scenarios: {
+        steady_mutations: {
+            executor: "constant-vus",
+            vus: __ENV.VUS ? parseInt(__ENV.VUS, 10) : 20,
+            duration: __ENV.DURATION || "5m",
+            gracefulStop: "30s",
+        },
+        ramp_up: {
+            executor: "ramping-vus",
+            startVUs: 0,
+            stages: [
+                {
+                    duration: "1m",
+                    target: __ENV.RAMP_TARGET
+                        ? parseInt(__ENV.RAMP_TARGET, 10)
+                        : 50,
+                },
+                {
+                    duration: "1m",
+                    target: __ENV.RAMP_TARGET
+                        ? parseInt(__ENV.RAMP_TARGET, 10)
+                        : 50,
+                },
+                { duration: "1m", target: 0 },
+            ],
+            gracefulStop: "30s",
+            startTime: "30s",
+        },
+    },
+    thresholds: {
+        http_req_failed: ["rate<0.02"], // < 2% failures
+        http_req_duration: ["p(90)<800", "p(99)<1500"], // latency SLO
+        "cart_add_item_duration{op:add}": ["p(90)<800"],
+        "cart_fetch_duration{op:get}": ["p(90)<600"],
+    },
+    summaryTrendStats: ["avg", "min", "med", "max", "p(90)", "p(95)", "p(99)"],
+};
+
+// ---------------- Metrics ----------------
+const addItemTrend = new Trend("cart_add_item_duration", true);
+const fetchTrend = new Trend("cart_fetch_duration", true);
+const checkoutTrend = new Trend("cart_checkout_duration", true);
+const addedItemsCounter = new Counter("cart_items_added");
+const checkoutCounter = new Counter("cart_checkout_calls");
+
+// ---------------- SKUs ----------------
+const SKUS = [
+    "778290",
+    "778345",
+    "778317",
+    "778277",
+    "778267",
+    "778376",
+    "778244",
+    "778384",
+    "778365",
+    "778377",
+    "778255",
+    "778286",
+    "778246",
+    "778270",
+    "778266",
+    "778285",
+    "778329",
+    "778425",
+    "778407",
+    "778418",
+    "778430",
+    "778469",
+    "778358",
+    "778351",
+    "778319",
+    "778307",
+    "778278",
+    "778251",
+    "778253",
+    "778261",
+    "778263",
+    "778273",
+    "778281",
+    "778294",
+    "778297",
+    "778302",
+];
+
+// ---------------- Helpers ----------------
+function randomSku() {
+    return SKUS[Math.floor(Math.random() * SKUS.length)];
+}
+function randomQty() {
+    return 1 + Math.floor(Math.random() * 3); // 1..3
+}
+function baseUrl() {
+    const u = __ENV.BASE_URL || "http://localhost:8080/cart";
+    // Allow user to pass either root host or full /cart path
+    return u.endsWith("/cart") ? u : u.replace(/\/+$/, "") + "/cart";
+}
+function extractCookie(res, name) {
+    const cookies = res.cookies[name];
+    if (!cookies || cookies.length === 0) return null;
+    return cookies[0].value;
+}
+function withCookies(headers, cookieJar) {
+    if (!cookieJar || Object.keys(cookieJar).length === 0) return headers;
+    const cookieStr = Object.entries(cookieJar)
+        .map(([k, v]) => `${k}=${v}`)
+        .join("; ");
+    return { ...headers, Cookie: cookieStr };
+}
+
+// Maintain cart + owner cookies per VU
+let cartState = {
+    cartid: null,
+    cartowner: null,
+};
+
+// Refresh cookies from response
+function updateCookies(res) {
+    const cid = extractCookie(res, "cartid");
+    if (cid) cartState.cartid = cid;
+    const owner = extractCookie(res, "cartowner");
+    if (owner) cartState.cartowner = owner;
+}
+
+// Build headers
+function headers() {
+    const h = { "Content-Type": "application/json" };
+    const jar = {};
+    if (cartState.cartid) jar["cartid"] = cartState.cartid;
+    if (cartState.cartowner) jar["cartowner"] = cartState.cartowner;
+    return withCookies(h, jar);
+}
+
+// Ensure cart exists (GET /)
+function ensureCart() {
+    if (cartState.cartid) return;
+    const res = http.get(baseUrl() + "/", { headers: headers() });
+    updateCookies(res);
+    check(res, {
+        "ensure cart status 200": (r) => r.status === 200,
+        "ensure cart has id": () => !!cartState.cartid,
+    });
+}
+
+// Add random item
+function addRandomItem() {
+    const payload = JSON.stringify({
+        sku: randomSku(),
+        quantity: randomQty(),
+        country: "no",
+    });
+    const start = Date.now();
+    const res = http.post(baseUrl(), payload, { headers: headers() });
+    const dur = Date.now() - start;
+    addItemTrend.add(dur, { op: "add" });
+    if (res.status === 200) {
+        addedItemsCounter.add(1);
+    }
+    updateCookies(res);
+    check(res, {
+        "add item status ok": (r) => r.status === 200,
+    });
+}
+
+// Fetch cart state
+function fetchCart() {
+    const start = Date.now();
+    const res = http.get(baseUrl() + "/", { headers: headers() });
+    const dur = Date.now() - start;
+    fetchTrend.add(dur, { op: "get" });
+    updateCookies(res);
+    check(res, { "fetch status ok": (r) => r.status === 200 });
+}
+
+// Occasional checkout trigger
+function maybeCheckout() {
+    if (!cartState.cartid) return;
+    // // Small probability
+    // if (Math.random() < 0.02) {
+    //     const start = Date.now();
+    //     const res = http.get(baseUrl() + "/checkout", { headers: headers() });
+    //     const dur = Date.now() - start;
+    //     checkoutTrend.add(dur, { op: "checkout" });
+    //     updateCookies(res);
+    //     if (res.status === 200) checkoutCounter.add(1);
+    //     check(res, { "checkout status ok": (r) => r.status === 200 });
+    // }
+}
+
+// ---------------- k6 lifecycle ----------------
+export function setup() {
+    // Provide SKU list length for summary
+    return { skuCount: SKUS.length };
+}
+
+export default function (data) {
+    group("cart flow", () => {
+        // Create or reuse cart
+        ensureCart();
+
+        // Random number of item mutations per iteration (1..5)
+        const ops = 1 + Math.floor(Math.random() * 5);
+        for (let i = 0; i < ops; i++) {
+            addRandomItem();
+        }
+
+        // Fetch state
+        fetchCart();
+
+        // Optional checkout attempt
+        maybeCheckout();
+    });
+
+    // Small think time
+    sleep(Math.random() * 0.5);
+}
+
+export function teardown(data) {
+    // Optionally we could GET confirmation or clear cart cookie
+    // Not implemented for load purpose.
+    console.log(`Test complete. SKU count: ${data.skuCount}`);
+}
+
+// ---------------- Summary ----------------
+export function handleSummary(data) {
+    return {
+        stdout: JSON.stringify(
+            {
+                metrics: {
+                    mutations_avg: data.metrics.cart_add_item_duration?.avg,
+                    mutations_p95: data.metrics.cart_add_item_duration?.p(95),
+                    fetch_p95: data.metrics.cart_fetch_duration?.p(95),
+                    checkout_count: data.metrics.cart_checkout_calls?.count,
+                },
+                checks: data.root_checks,
+            },
+            null,
+            2,
+        ),
+    };
+}

main.go

@@ -38,15 +38,20 @@ var (
 func spawn(id CartId) (*CartGrain, error) {
 	grainSpawns.Inc()
 	ret := &CartGrain{
-		lastItemId:      0,
-		lastDeliveryId:  0,
-		Deliveries:      []*CartDelivery{},
-		Id:              id,
-		Items:           []*CartItem{},
-		storageMessages: []Message{},
-		TotalPrice:      0,
+		lastItemId:     0,
+		lastDeliveryId: 0,
+		Deliveries:     []*CartDelivery{},
+		Id:             id,
+		Items:          []*CartItem{},
+		TotalPrice:     0,
 	}
-	err := loadMessages(ret, id)
+	// Set baseline lastChange at spawn; replay may update it to last event timestamp.
+	ret.lastChange = time.Now().Unix()
+
+	// Legacy loadMessages (no-op) retained; then replay append-only event log
+	//_ = loadMessages(ret, id)
+	err := ReplayCartEvents(ret, id)
+
 	return ret, err
 }
 
@@ -55,41 +60,24 @@ func init() {
 }
 
 type App struct {
-	pool    *GrainLocalPool
+	pool    *CartPool
 	storage *DiskStorage
 }
 
 func (a *App) Save() error {
-	hasChanges := false
-	a.pool.mu.RLock()
-	defer a.pool.mu.RUnlock()
-	for id, grain := range a.pool.GetGrains() {
+	for id, grain := range a.pool.SnapshotGrains() {
 		if grain == nil {
 			continue
 		}
-		if grain.GetLastChange() > a.storage.LastSaves[id] {
-			hasChanges = true
+		if grain.GetLastChange() > a.storage.LastSaves[uint64(id)] {
+
 			err := a.storage.Store(id, grain)
 			if err != nil {
 				log.Printf("Error saving grain %s: %v\n", id, err)
 			}
 		}
 	}
-
-	if !hasChanges {
-		return nil
-	}
-	return a.storage.saveState()
-}
-
-func (a *App) HandleSave(w http.ResponseWriter, r *http.Request) {
-	err := a.Save()
-	if err != nil {
-		w.WriteHeader(http.StatusInternalServerError)
-		w.Write([]byte(err.Error()))
-	} else {
-		w.WriteHeader(http.StatusCreated)
-	}
+	return nil
 }
 
 var podIp = os.Getenv("POD_IP")
@@ -97,23 +85,6 @@ var name = os.Getenv("POD_NAME")
 var amqpUrl = os.Getenv("AMQP_URL")
 var KlarnaInstance = NewKlarnaClient(KlarnaPlaygroundUrl, os.Getenv("KLARNA_API_USERNAME"), os.Getenv("KLARNA_API_PASSWORD"))
 
-func GetDiscovery() Discovery {
-	if podIp == "" {
-		return nil
-	}
-
-	config, kerr := rest.InClusterConfig()
-
-	if kerr != nil {
-		log.Fatalf("Error creating kubernetes client: %v\n", kerr)
-	}
-	client, err := kubernetes.NewForConfig(config)
-	if err != nil {
-		log.Fatalf("Error creating client: %v\n", err)
-	}
-	return NewK8sDiscovery(client)
-}
-
 var tpl = `<!DOCTYPE html>
 <html lang="en">
   <head>
@@ -135,50 +106,45 @@ func getCountryFromHost(host string) string {
 	return "se"
 }
 
-func getCheckoutOrder(host string, cartId CartId) *messages.CreateCheckoutOrder {
-	baseUrl := fmt.Sprintf("https://%s", host)
-	cartBaseUrl := os.Getenv("CART_BASE_URL")
-	if cartBaseUrl == "" {
-		cartBaseUrl = "https://cart.tornberg.me"
+func GetDiscovery() Discovery {
+	if podIp == "" {
+		return nil
 	}
-	country := getCountryFromHost(host)
 
-	return &messages.CreateCheckoutOrder{
-		Terms:        fmt.Sprintf("%s/terms", baseUrl),
-		Checkout:     fmt.Sprintf("%s/checkout?order_id={checkout.order.id}", baseUrl),
-		Confirmation: fmt.Sprintf("%s/confirmation/{checkout.order.id}", baseUrl),
-		Validation:   fmt.Sprintf("%s/validation", cartBaseUrl),
-		Push:         fmt.Sprintf("%s/push?order_id={checkout.order.id}", cartBaseUrl),
-		Country:      country,
+	config, kerr := rest.InClusterConfig()
+
+	if kerr != nil {
+		log.Fatalf("Error creating kubernetes client: %v\n", kerr)
 	}
+	client, err := kubernetes.NewForConfig(config)
+	if err != nil {
+		log.Fatalf("Error creating client: %v\n", err)
+	}
+	return NewK8sDiscovery(client)
 }
 
 func main() {
-
-	storage, err := NewDiskStorage(fmt.Sprintf("data/%s_state.gob", name))
+	storage, err := NewDiskStorage(fmt.Sprintf("data/s_%s.gob", name))
 	if err != nil {
 		log.Printf("Error loading state: %v\n", err)
 	}
+	pool, err := NewCartPool(2*65535, 15*time.Minute, podIp, spawn, GetDiscovery())
+	if err != nil {
+		log.Fatalf("Error creating cart pool: %v\n", err)
+	}
 	app := &App{
-		pool:    NewGrainLocalPool(65535, 5*time.Minute, spawn),
+		pool:    pool,
 		storage: storage,
 	}
 
-	syncedPool, err := NewSyncedPool(app.pool, podIp, GetDiscovery())
-	if err != nil {
-		log.Fatalf("Error creating synced pool: %v\n", err)
-	}
-
-	// Start unified gRPC server (CartActor + ControlPlane) replacing legacy RPC server on :1337
-	// TODO: Remove any remaining legacy RPC server references and deprecated frame-based code after full gRPC migration is validated.
-	grpcSrv, err := StartGRPCServer(":1337", app.pool, syncedPool)
+	grpcSrv, err := StartGRPCServer(":1337", pool)
 	if err != nil {
 		log.Fatalf("Error starting gRPC server: %v\n", err)
 	}
 	defer grpcSrv.GracefulStop()
 
 	go func() {
-		for range time.Tick(time.Minute * 10) {
+		for range time.Tick(time.Minute * 5) {
 			err := app.Save()
 			if err != nil {
 				log.Printf("Error saving: %v\n", err)
@@ -189,7 +155,7 @@ func main() {
 		Url: amqpUrl,
 	}
 
-	syncedServer := NewPoolServer(syncedPool, fmt.Sprintf("%s, %s", name, podIp))
+	syncedServer := NewPoolServer(pool, fmt.Sprintf("%s, %s", name, podIp))
 	mux := http.NewServeMux()
 	mux.Handle("/cart/", http.StripPrefix("/cart", syncedServer.Serve()))
 	// only for local
@@ -206,16 +172,13 @@ func main() {
 	mux.Handle("/metrics", promhttp.Handler())
 	mux.HandleFunc("/healthz", func(w http.ResponseWriter, r *http.Request) {
 		// Grain pool health: simple capacity check (mirrors previous GrainHandler.IsHealthy)
-		app.pool.mu.RLock()
-		grainCount := len(app.pool.grains)
-		capacity := app.pool.PoolSize
-		app.pool.mu.RUnlock()
+		grainCount, capacity := app.pool.LocalUsage()
 		if grainCount >= capacity {
 			w.WriteHeader(http.StatusInternalServerError)
 			w.Write([]byte("grain pool at capacity"))
 			return
 		}
-		if !syncedPool.IsHealthy() {
+		if !pool.IsHealthy() {
 			w.WriteHeader(http.StatusInternalServerError)
 			w.Write([]byte("control plane not healthy"))
 			return
@@ -248,29 +211,27 @@ func main() {
 				w.Write([]byte("no cart id to checkout is empty"))
 				return
 			}
-			cartId := ToCartId(cookie.Value)
-			reply, err := syncedServer.pool.Process(cartId, Message{
-				Type:    CreateCheckoutOrderType,
-				Content: getCheckoutOrder(r.Host, cartId),
-			})
-			if err != nil {
-				w.WriteHeader(http.StatusInternalServerError)
-				w.Write([]byte(err.Error()))
-			}
-			err = json.Unmarshal(reply.Payload, &order)
-			if err != nil {
-				w.WriteHeader(http.StatusInternalServerError)
-				w.Write([]byte(err.Error()))
+			parsed, ok := ParseCartId(cookie.Value)
+			if !ok {
+				w.WriteHeader(http.StatusBadRequest)
+				w.Write([]byte("invalid cart id format"))
 				return
 			}
+			cartId := parsed
+			order, err = syncedServer.CreateOrUpdateCheckout(r.Host, cartId)
+			if err != nil {
+				w.WriteHeader(http.StatusInternalServerError)
+				w.Write([]byte(err.Error()))
+			}
+			// v2: Apply now returns *CartGrain; order creation handled inside grain (no payload to unmarshal)
 		} else {
-			prevOrder, err := KlarnaInstance.GetOrder(orderId)
+			order, err = KlarnaInstance.GetOrder(orderId)
 			if err != nil {
 				w.WriteHeader(http.StatusBadRequest)
 				w.Write([]byte(err.Error()))
 				return
 			}
-			order = prevOrder
+
 		}
 		w.Header().Set("Content-Type", "text/html; charset=utf-8")
 		w.Header().Set("Permissions-Policy", "payment=(self \"https://js.stripe.com\" \"https://m.stripe.network\" \"https://js.playground.kustom.co\")")
@@ -380,8 +341,9 @@ func main() {
 	go func() {
 		sig := <-sigs
 		fmt.Println("Shutting down due to signal:", sig)
-		go syncedPool.Close()
 		app.Save()
+		pool.Close()
+
 		done <- true
 	}()
 
@@ -392,14 +354,19 @@ func main() {
 }
 
 func triggerOrderCompleted(err error, syncedServer *PoolServer, order *CheckoutOrder) error {
-	_, err = syncedServer.pool.Process(ToCartId(order.MerchantReference1), Message{
-		Type: OrderCompletedType,
-		Content: &messages.OrderCreated{
-			OrderId: order.ID,
-			Status:  order.Status,
-		},
-	})
-	return err
+	mutation := &messages.OrderCreated{
+		OrderId: order.ID,
+		Status:  order.Status,
+	}
+	cid, ok := ParseCartId(order.MerchantReference1)
+	if !ok {
+		return fmt.Errorf("invalid cart id in order reference: %s", order.MerchantReference1)
+	}
+	_, applyErr := syncedServer.pool.Apply(cid, mutation)
+	if applyErr == nil {
+		_ = AppendCartEvent(cid, mutation)
+	}
+	return applyErr
 }
 
 func confirmOrder(order *CheckoutOrder, orderHandler *AmqpOrderHandler) error {

message-handler.go

@@ -1,315 +0,0 @@
-package main
-
-import (
-	"fmt"
-	"io"
-
-	messages "git.tornberg.me/go-cart-actor/proto"
-	"google.golang.org/protobuf/proto"
-)
-
-var Handlers = map[uint16]MessageHandler{
-	AddRequestType:          &AddRequestHandler{},
-	AddItemType:             &AddItemHandler{},
-	ChangeQuantityType:      &ChangeQuantityHandler{},
-	SetDeliveryType:         &SetDeliveryHandler{},
-	RemoveItemType:          &RemoveItemHandler{},
-	RemoveDeliveryType:      &RemoveDeliveryHandler{},
-	CreateCheckoutOrderType: &CheckoutHandler{},
-	SetCartItemsType:        &SetCartItemsHandler{},
-	OrderCompletedType:      &OrderCompletedHandler{},
-}
-
-func GetMessageHandler(t uint16) (MessageHandler, error) {
-	h, ok := Handlers[t]
-	if !ok {
-		return nil, fmt.Errorf("no handler for message type %d", t)
-	}
-	return h, nil
-}
-
-type MessageHandler interface {
-	Write(*Message, io.Writer) error
-	Read(data []byte) (interface{}, error)
-	Is(*Message) bool
-}
-type TypedMessageHandler struct {
-	Type uint16
-}
-
-type SetCartItemsHandler struct {
-	TypedMessageHandler
-}
-
-func (h *SetCartItemsHandler) Write(m *Message, w io.Writer) error {
-	messageBytes, err := proto.Marshal(m.Content.(*messages.SetCartRequest))
-	if err != nil {
-		return err
-	}
-	w.Write(messageBytes)
-	return nil
-}
-
-func (h *SetCartItemsHandler) Read(data []byte) (interface{}, error) {
-	msg := &messages.SetCartRequest{}
-
-	err := proto.Unmarshal(data, msg)
-	if err != nil {
-		return nil, err
-	}
-	return msg, nil
-}
-
-func (h *SetCartItemsHandler) Is(m *Message) bool {
-	if m.Type != AddRequestType {
-		return false
-	}
-	_, ok := m.Content.(*messages.SetCartRequest)
-	return ok
-}
-
-type AddRequestHandler struct {
-	TypedMessageHandler
-}
-
-func (h *AddRequestHandler) Write(m *Message, w io.Writer) error {
-	messageBytes, err := proto.Marshal(m.Content.(*messages.AddRequest))
-	if err != nil {
-		return err
-	}
-	w.Write(messageBytes)
-	return nil
-}
-
-func (h *AddRequestHandler) Read(data []byte) (interface{}, error) {
-	msg := &messages.AddRequest{}
-
-	err := proto.Unmarshal(data, msg)
-	if err != nil {
-		return nil, err
-	}
-	return msg, nil
-}
-
-func (h *AddRequestHandler) Is(m *Message) bool {
-	if m.Type != AddRequestType {
-		return false
-	}
-	_, ok := m.Content.(*messages.AddRequest)
-	return ok
-}
-
-type AddItemHandler struct {
-	TypedMessageHandler
-}
-
-func (h *AddItemHandler) Write(m *Message, w io.Writer) error {
-	messageBytes, err := proto.Marshal(m.Content.(*messages.AddItem))
-	if err != nil {
-		return err
-	}
-	w.Write(messageBytes)
-	return nil
-}
-
-func (h *AddItemHandler) Read(data []byte) (interface{}, error) {
-	msg := &messages.AddItem{}
-
-	err := proto.Unmarshal(data, msg)
-	if err != nil {
-		return nil, err
-	}
-	return msg, nil
-}
-
-func (h *AddItemHandler) Is(m *Message) bool {
-	if m.Type != AddItemType {
-		return false
-	}
-	_, ok := m.Content.(*messages.AddItem)
-	return ok
-}
-
-type ChangeQuantityHandler struct {
-	TypedMessageHandler
-}
-
-func (h *ChangeQuantityHandler) Write(m *Message, w io.Writer) error {
-	messageBytes, err := proto.Marshal(m.Content.(*messages.ChangeQuantity))
-	if err != nil {
-		return err
-	}
-	w.Write(messageBytes)
-	return nil
-}
-
-func (h *ChangeQuantityHandler) Read(data []byte) (interface{}, error) {
-	msg := &messages.ChangeQuantity{}
-
-	err := proto.Unmarshal(data, msg)
-	if err != nil {
-		return nil, err
-	}
-	return msg, nil
-}
-
-func (h *ChangeQuantityHandler) Is(m *Message) bool {
-	if m.Type != ChangeQuantityType {
-		return false
-	}
-	_, ok := m.Content.(*messages.ChangeQuantity)
-	return ok
-}
-
-type SetDeliveryHandler struct {
-	TypedMessageHandler
-}
-
-func (h *SetDeliveryHandler) Write(m *Message, w io.Writer) error {
-	messageBytes, err := proto.Marshal(m.Content.(*messages.SetDelivery))
-	if err != nil {
-		return err
-	}
-	w.Write(messageBytes)
-	return nil
-}
-
-func (h *SetDeliveryHandler) Read(data []byte) (interface{}, error) {
-	msg := &messages.SetDelivery{}
-
-	err := proto.Unmarshal(data, msg)
-	if err != nil {
-		return nil, err
-	}
-	return msg, nil
-}
-
-func (h *SetDeliveryHandler) Is(m *Message) bool {
-	if m.Type != ChangeQuantityType {
-		return false
-	}
-	_, ok := m.Content.(*messages.SetDelivery)
-	return ok
-}
-
-type RemoveItemHandler struct {
-	TypedMessageHandler
-}
-
-func (h *RemoveItemHandler) Write(m *Message, w io.Writer) error {
-	messageBytes, err := proto.Marshal(m.Content.(*messages.RemoveItem))
-	if err != nil {
-		return err
-	}
-	w.Write(messageBytes)
-	return nil
-}
-
-func (h *RemoveItemHandler) Read(data []byte) (interface{}, error) {
-	msg := &messages.RemoveItem{}
-
-	err := proto.Unmarshal(data, msg)
-	if err != nil {
-		return nil, err
-	}
-	return msg, nil
-}
-
-func (h *RemoveItemHandler) Is(m *Message) bool {
-	if m.Type != AddItemType {
-		return false
-	}
-	_, ok := m.Content.(*messages.RemoveItem)
-	return ok
-}
-
-type RemoveDeliveryHandler struct {
-	TypedMessageHandler
-}
-
-func (h *RemoveDeliveryHandler) Write(m *Message, w io.Writer) error {
-	messageBytes, err := proto.Marshal(m.Content.(*messages.RemoveDelivery))
-	if err != nil {
-		return err
-	}
-	w.Write(messageBytes)
-	return nil
-}
-
-func (h *RemoveDeliveryHandler) Read(data []byte) (interface{}, error) {
-	msg := &messages.RemoveDelivery{}
-
-	err := proto.Unmarshal(data, msg)
-	if err != nil {
-		return nil, err
-	}
-	return msg, nil
-}
-
-func (h *RemoveDeliveryHandler) Is(m *Message) bool {
-	if m.Type != AddItemType {
-		return false
-	}
-	_, ok := m.Content.(*messages.RemoveDelivery)
-	return ok
-}
-
-type CheckoutHandler struct {
-	TypedMessageHandler
-}
-
-func (h *CheckoutHandler) Write(m *Message, w io.Writer) error {
-	messageBytes, err := proto.Marshal(m.Content.(*messages.CreateCheckoutOrder))
-	if err != nil {
-		return err
-	}
-	w.Write(messageBytes)
-	return nil
-}
-
-func (h *CheckoutHandler) Read(data []byte) (interface{}, error) {
-	msg := &messages.CreateCheckoutOrder{}
-
-	err := proto.Unmarshal(data, msg)
-	if err != nil {
-		return nil, err
-	}
-	return msg, nil
-}
-
-func (h *CheckoutHandler) Is(m *Message) bool {
-	if m.Type != CreateCheckoutOrderType {
-		return false
-	}
-	_, ok := m.Content.(*messages.CreateCheckoutOrder)
-	return ok
-}
-
-type OrderCompletedHandler struct {
-	TypedMessageHandler
-}
-
-func (h *OrderCompletedHandler) Write(m *Message, w io.Writer) error {
-	messageBytes, err := proto.Marshal(m.Content.(*messages.OrderCreated))
-	if err != nil {
-		return err
-	}
-	w.Write(messageBytes)
-	return nil
-}
-func (h *OrderCompletedHandler) Read(data []byte) (interface{}, error) {
-	msg := &messages.OrderCreated{}
-
-	err := proto.Unmarshal(data, msg)
-	if err != nil {
-		return nil, err
-	}
-	return msg, nil
-}
-func (h *OrderCompletedHandler) Is(m *Message) bool {
-	if m.Type != OrderCompletedType {
-		return false
-	}
-	_, ok := m.Content.(*messages.OrderCreated)
-	return ok
-}

message-types.go

@@ -1,15 +0,0 @@
-package main
-
-const (
-	AddRequestType = 1
-	AddItemType    = 2
-
-	RemoveItemType          = 4
-	RemoveDeliveryType      = 5
-	ChangeQuantityType      = 6
-	SetDeliveryType         = 7
-	SetPickupPointType      = 8
-	CreateCheckoutOrderType = 9
-	SetCartItemsType        = 10
-	OrderCompletedType      = 11
-)

message.go

@@ -1,94 +0,0 @@
-package main
-
-import (
-	"bytes"
-	"encoding/binary"
-	"io"
-	"time"
-)
-
-type StorableMessage interface {
-	Write(w io.Writer) error
-}
-
-type Message struct {
-	Type      uint16
-	TimeStamp *int64
-	Content   interface{}
-}
-
-type MessageWriter struct {
-	io.Writer
-}
-
-type StorableMessageHeader struct {
-	Version    uint16
-	Type       uint16
-	TimeStamp  int64
-	DataLength uint64
-}
-
-func GetData(fn func(w io.Writer) error) ([]byte, error) {
-	var buf bytes.Buffer
-	err := fn(&buf)
-	if err != nil {
-		return nil, err
-	}
-	b := buf.Bytes()
-	return b, nil
-}
-
-func (m Message) Write(w io.Writer) error {
-	h, err := GetMessageHandler(m.Type)
-	if err != nil {
-		return err
-	}
-	data, err := GetData(func(w io.Writer) error {
-		return h.Write(&m, w)
-	})
-	if err != nil {
-		return err
-	}
-	ts := time.Now().Unix()
-	if m.TimeStamp != nil {
-		ts = *m.TimeStamp
-	}
-
-	err = binary.Write(w, binary.LittleEndian, StorableMessageHeader{
-		Version:    1,
-		Type:       m.Type,
-		TimeStamp:  ts,
-		DataLength: uint64(len(data)),
-	})
-	w.Write(data)
-
-	return err
-}
-
-func ReadMessage(reader io.Reader, m *Message) error {
-
-	header := StorableMessageHeader{}
-	err := binary.Read(reader, binary.LittleEndian, &header)
-	if err != nil {
-		return err
-	}
-	messageBytes := make([]byte, header.DataLength)
-	_, err = reader.Read(messageBytes)
-	if err != nil {
-		return err
-	}
-	h, err := GetMessageHandler(header.Type)
-	if err != nil {
-		return err
-	}
-	content, err := h.Read(messageBytes)
-	if err != nil {
-		return err
-	}
-	m.Content = content
-
-	m.Type = header.Type
-	m.TimeStamp = &header.TimeStamp
-
-	return nil
-}

mutation_add_item.go

@@ -0,0 +1,82 @@
+package main
+
+import (
+	"fmt"
+
+	messages "git.tornberg.me/go-cart-actor/proto"
+)
+
+// mutation_add_item.go
+//
+// Registers the AddItem cart mutation in the generic mutation registry.
+// This replaces the legacy switch-based logic previously found in CartGrain.Apply.
+//
+// Behavior:
+//   * Validates quantity > 0
+//   * If an item with same SKU exists -> increases quantity
+//   * Else creates a new CartItem with computed tax amounts
+//   * Totals recalculated automatically via WithTotals()
+//
+// NOTE: Any future field additions in messages.AddItem that affect pricing / tax
+// must keep this handler in sync.
+
+func init() {
+	RegisterMutation[messages.AddItem](
+		"AddItem",
+		func(g *CartGrain, m *messages.AddItem) error {
+			if m == nil {
+				return fmt.Errorf("AddItem: nil payload")
+			}
+			if m.Quantity < 1 {
+				return fmt.Errorf("AddItem: invalid quantity %d", m.Quantity)
+			}
+
+			// Fast path: merge with existing item having same SKU
+			if existing, found := g.FindItemWithSku(m.Sku); found {
+				existing.Quantity += int(m.Quantity)
+				return nil
+			}
+
+			g.mu.Lock()
+			defer g.mu.Unlock()
+
+			g.lastItemId++
+			taxRate := 2500
+			if m.Tax > 0 {
+				taxRate = int(m.Tax)
+			}
+			taxAmountPerUnit := GetTaxAmount(m.Price, taxRate)
+
+			g.Items = append(g.Items, &CartItem{
+				Id:          g.lastItemId,
+				ItemId:      int(m.ItemId),
+				Quantity:    int(m.Quantity),
+				Sku:         m.Sku,
+				Name:        m.Name,
+				Price:       m.Price,
+				TotalPrice:  m.Price * int64(m.Quantity),
+				TotalTax:    int64(taxAmountPerUnit * int64(m.Quantity)),
+				Image:       m.Image,
+				Stock:       StockStatus(m.Stock),
+				Disclaimer:  m.Disclaimer,
+				Brand:       m.Brand,
+				Category:    m.Category,
+				Category2:   m.Category2,
+				Category3:   m.Category3,
+				Category4:   m.Category4,
+				Category5:   m.Category5,
+				OrgPrice:    m.OrgPrice,
+				ArticleType: m.ArticleType,
+				Outlet:      m.Outlet,
+				SellerId:    m.SellerId,
+				SellerName:  m.SellerName,
+				Tax:         int(taxAmountPerUnit),
+				TaxRate:     taxRate,
+				StoreId:     m.StoreId,
+			})
+
+			return nil
+		},
+		WithTotals(), // Recalculate totals after successful mutation
+	)
+}

mutation_add_request.go

@@ -0,0 +1,61 @@
+package main
+
+import (
+	"fmt"
+
+	messages "git.tornberg.me/go-cart-actor/proto"
+)
+
+// mutation_add_request.go
+//
+// Registers the AddRequest mutation. This mutation is a higher-level intent
+// (add by SKU + quantity) which may translate into either:
+//   - Increasing quantity of an existing line (same SKU), OR
+//   - Creating a new item by performing a product lookup (via getItemData inside CartGrain.AddItem)
+//
+// Behavior:
+//   - Validates non-empty SKU and quantity > 0
+//   - If an item with the SKU already exists: increments its quantity
+//   - Else delegates to CartGrain.AddItem (which itself produces an AddItem mutation)
+//   - Totals recalculated automatically (WithTotals)
+//
+// NOTE:
+//   - This handler purposely avoids duplicating the detailed AddItem logic;
+//     it reuses CartGrain.AddItem which then flows through the AddItem mutation
+//     registry handler.
+//   - Double total recalculation can occur (AddItem has WithTotals too), but
+//     is acceptable for clarity. Optimize later if needed.
+//
+// Potential future improvements:
+//   - Stock validation before increasing quantity
+//   - Reservation logic or concurrency guards around stock updates
+//   - Coupon / pricing rules applied conditionally during add-by-sku
+func init() {
+	RegisterMutation[messages.AddRequest](
+		"AddRequest",
+		func(g *CartGrain, m *messages.AddRequest) error {
+			if m == nil {
+				return fmt.Errorf("AddRequest: nil payload")
+			}
+			if m.Sku == "" {
+				return fmt.Errorf("AddRequest: sku is empty")
+			}
+			if m.Quantity < 1 {
+				return fmt.Errorf("AddRequest: invalid quantity %d", m.Quantity)
+			}
+
+			// Existing line: accumulate quantity only.
+			if existing, found := g.FindItemWithSku(m.Sku); found {
+				existing.Quantity += int(m.Quantity)
+				return nil
+			}
+
+			// New line: delegate to higher-level AddItem flow (product lookup).
+			// We intentionally ignore the returned *CartGrain; registry will
+			// do totals again after this handler returns (harmless).
+			_, err := g.AddItem(m.Sku, int(m.Quantity), m.Country, m.StoreId)
+			return err
+		},
+		WithTotals(),
+	)
+}

mutation_change_quantity.go

@@ -0,0 +1,58 @@
+package main
+
+import (
+	"fmt"
+
+	messages "git.tornberg.me/go-cart-actor/proto"
+)
+
+// mutation_change_quantity.go
+//
+// Registers the ChangeQuantity mutation.
+//
+// Behavior:
+//   - Locates an item by its cart-local line item Id (not source item_id).
+//   - If requested quantity <= 0 the line is removed.
+//   - Otherwise the line's Quantity field is updated.
+//   - Totals are recalculated (WithTotals).
+//
+// Error handling:
+//   - Returns an error if the item Id is not found.
+//   - Returns an error if payload is nil (defensive).
+//
+// Concurrency:
+//   - Uses the grain's RW-safe mutation pattern: we mutate in place under
+//     the grain's implicit expectation that higher layers control access.
+//     (If strict locking is required around every mutation, wrap logic in
+//     an explicit g.mu.Lock()/Unlock(), but current model mirrors prior code.)
+func init() {
+	RegisterMutation[messages.ChangeQuantity](
+		"ChangeQuantity",
+		func(g *CartGrain, m *messages.ChangeQuantity) error {
+			if m == nil {
+				return fmt.Errorf("ChangeQuantity: nil payload")
+			}
+
+			foundIndex := -1
+			for i, it := range g.Items {
+				if it.Id == int(m.Id) {
+					foundIndex = i
+					break
+				}
+			}
+			if foundIndex == -1 {
+				return fmt.Errorf("ChangeQuantity: item id %d not found", m.Id)
+			}
+
+			if m.Quantity <= 0 {
+				// Remove the item
+				g.Items = append(g.Items[:foundIndex], g.Items[foundIndex+1:]...)
+				return nil
+			}
+
+			g.Items[foundIndex].Quantity = int(m.Quantity)
+			return nil
+		},
+		WithTotals(),
+	)
+}

mutation_initialize_checkout.go

@@ -0,0 +1,49 @@
+package main
+
+import (
+	"fmt"
+
+	messages "git.tornberg.me/go-cart-actor/proto"
+)
+
+// mutation_initialize_checkout.go
+//
+// Registers the InitializeCheckout mutation.
+// This mutation is invoked AFTER an external Klarna checkout session
+// has been successfully created or updated. It persists the Klarna
+// order reference / status and marks the cart as having a payment in progress.
+//
+// Behavior:
+//   - Sets OrderReference to the Klarna order ID (overwriting if already set).
+//   - Sets PaymentStatus to the current Klarna status.
+//   - Sets / updates PaymentInProgress flag.
+//   - Does NOT alter pricing or line items (so no totals recalculation).
+//
+// Validation:
+//   - Returns an error if payload is nil.
+//   - Returns an error if orderId is empty (integrity guard).
+//
+// Concurrency:
+//   - Relies on upstream mutation serialization for a single grain. If
+//     parallel checkout attempts are possible, add higher-level guards
+//     (e.g. reject if PaymentInProgress already true unless reusing
+//     the same OrderReference).
+func init() {
+	RegisterMutation[messages.InitializeCheckout](
+		"InitializeCheckout",
+		func(g *CartGrain, m *messages.InitializeCheckout) error {
+			if m == nil {
+				return fmt.Errorf("InitializeCheckout: nil payload")
+			}
+			if m.OrderId == "" {
+				return fmt.Errorf("InitializeCheckout: missing orderId")
+			}
+
+			g.OrderReference = m.OrderId
+			g.PaymentStatus = m.Status
+			g.PaymentInProgress = m.PaymentInProgress
+			return nil
+		},
+		// No WithTotals(): monetary aggregates are unaffected.
+	)
+}

mutation_order_created.go

@@ -0,0 +1,53 @@
+package main
+
+import (
+	"fmt"
+
+	messages "git.tornberg.me/go-cart-actor/proto"
+)
+
+// mutation_order_created.go
+//
+// Registers the OrderCreated mutation.
+//
+// This mutation represents the completion (or state transition) of an order
+// initiated earlier via InitializeCheckout / external Klarna processing.
+// It finalizes (or updates) the cart's order metadata.
+//
+// Behavior:
+//   - Validates payload non-nil and OrderId not empty.
+//   - Sets (or overwrites) OrderReference with the provided OrderId.
+//   - Sets PaymentStatus from payload.Status.
+//   - Marks PaymentInProgress = false (checkout flow finished / acknowledged).
+//   - Does NOT adjust monetary totals (no WithTotals()).
+//
+// Notes / Future Extensions:
+//   - If multiple order completion events can arrive (e.g., retries / webhook
+//     replays), this handler is idempotent: it simply overwrites fields.
+//   - If you need to guard against conflicting order IDs, add a check:
+//     if g.OrderReference != "" && g.OrderReference != m.OrderId { ... }
+//   - Add audit logging or metrics here if required.
+//
+// Concurrency:
+//   - Relies on the higher-level guarantee that Apply() calls are serialized
+//     per grain. If out-of-order events are possible, embed versioning or
+//     timestamps in the mutation and compare before applying changes.
+func init() {
+	RegisterMutation[messages.OrderCreated](
+		"OrderCreated",
+		func(g *CartGrain, m *messages.OrderCreated) error {
+			if m == nil {
+				return fmt.Errorf("OrderCreated: nil payload")
+			}
+			if m.OrderId == "" {
+				return fmt.Errorf("OrderCreated: missing orderId")
+			}
+
+			g.OrderReference = m.OrderId
+			g.PaymentStatus = m.Status
+			g.PaymentInProgress = false
+			return nil
+		},
+		// No WithTotals(): order completion does not modify pricing or taxes.
+	)
+}

mutation_registry.go

@@ -0,0 +1,301 @@
+package main
+
+import (
+	"fmt"
+	"reflect"
+	"sync"
+)
+
+// mutation_registry.go
+//
+// Mutation Registry Infrastructure
+// --------------------------------
+// This file introduces a generic registry for cart mutations that:
+//
+// 1. Decouples mutation logic from the large type-switch inside CartGrain.Apply.
+// 2. Enforces (at registration time) that every mutation handler has the correct
+//    signature: func(*CartGrain, *T) error
+// 3. Optionally auto-updates cart totals after a mutation if flagged.
+// 4. Provides a single authoritative list of registered mutations for
+//    introspection / coverage testing.
+// 5. Allows incremental migration: you can first register new mutations here,
+//    and later prune the legacy switch cases.
+//
+// Usage Pattern
+// -------------
+//   // Define your mutation proto message (e.g. messages.ApplyCoupon in messages.proto)
+//   // Regenerate protobufs.
+//
+//   // In an init() (ideally in a small file like mutations_apply_coupon.go)
+//   func init() {
+//       RegisterMutation[*messages.ApplyCoupon](
+//           "ApplyCoupon",
+//           func(g *CartGrain, m *messages.ApplyCoupon) error {
+//               // domain logic ...
+//               discount := int64(5000)
+//               if g.TotalPrice < discount {
+//                   discount = g.TotalPrice
+//               }
+//               g.TotalDiscount += discount
+//               g.TotalPrice -= discount
+//               return nil
+//           },
+//           WithTotals(), // we changed price-related fields; recalc totals
+//       )
+//   }
+//
+//   // To invoke dynamically (alternative to the current switch):
+//   if updated, err := ApplyRegistered(grain, incomingMessage); err == nil {
+//       grain = updated
+//   } else if errors.Is(err, ErrMutationNotRegistered) {
+//       // fallback to legacy switch logic
+//   }
+//
+// Migration Strategy
+// ------------------
+// 1. For each existing mutation handled in CartGrain.Apply, add a registry
+//    registration with equivalent logic.
+// 2. Add a test that enumerates all *expected* mutation proto types and asserts
+//    they are present in RegisteredMutationTypes().
+// 3. Once coverage is 100%, replace the switch in CartGrain.Apply with a call
+//    to ApplyRegistered (and optionally keep a minimal default to produce an
+//    "unsupported mutation" error).
+//
+// Thread Safety
+// -------------
+// Registration is typically done at init() time; a RWMutex provides safety
+// should late dynamic registration ever be introduced.
+//
+// Auto Totals
+// -----------
+// Many mutations require recomputing totals. To avoid forgetting this, pass
+// WithTotals() when registering. This will invoke grain.UpdateTotals() after
+// the handler returns successfully.
+//
+// Error Semantics
+// ---------------
+// - If a handler returns an error, totals are NOT recalculated (even if
+//   WithTotals() was specified).
+// - ApplyRegistered returns (nil, ErrMutationNotRegistered) if the message type
+//   is absent.
+//
+// Extensibility
+// -------------
+// It is straightforward to add options like audit hooks, metrics wrappers,
+// or optimistic concurrency guards by extending MutationOption.
+//
+// NOTE: Generics require Go 1.18+. If constrained to earlier Go versions,
+//       replace the generic registration with a non-generic RegisterMutationType
+//       that accepts reflect.Type and an adapter function.
+//
+// ---------------------------------------------------------------------------
+
+var (
+	mutationRegistryMu sync.RWMutex
+	mutationRegistry   = make(map[reflect.Type]*registeredMutation)
+
+	// ErrMutationNotRegistered is returned when no handler exists for a given mutation type.
+	ErrMutationNotRegistered = fmt.Errorf("mutation not registered")
+)
+
+// MutationOption configures additional behavior for a registered mutation.
+type MutationOption func(*mutationOptions)
+
+// mutationOptions holds flags adjustable per registration.
+type mutationOptions struct {
+	updateTotals bool
+}
+
+// WithTotals ensures CartGrain.UpdateTotals() is called after a successful handler.
+func WithTotals() MutationOption {
+	return func(o *mutationOptions) {
+		o.updateTotals = true
+	}
+}
+
+// registeredMutation stores metadata + the execution closure.
+type registeredMutation struct {
+	name         string
+	handler      func(*CartGrain, interface{}) error
+	updateTotals bool
+	msgType      reflect.Type
+}
+
+// RegisterMutation registers a mutation handler for a specific message type T.
+//
+// Parameters:
+//
+//	name    - a human-readable identifier (used for diagnostics / coverage tests).
+//	handler - business logic operating on the cart grain & strongly typed message.
+//	options - optional behavior flags (e.g., WithTotals()).
+//
+// Panics if:
+//   - name is empty
+//   - handler is nil
+//   - duplicate registration for the same message type T
+//
+// Typical call is placed in an init() function.
+func RegisterMutation[T any](name string, handler func(*CartGrain, *T) error, options ...MutationOption) {
+	if name == "" {
+		panic("RegisterMutation: name is required")
+	}
+	if handler == nil {
+		panic("RegisterMutation: handler is nil")
+	}
+
+	// Derive the reflect.Type for *T then its Elem (T) for mapping.
+	var zero *T
+	rtPtr := reflect.TypeOf(zero)
+	if rtPtr.Kind() != reflect.Ptr {
+		panic("RegisterMutation: expected pointer type for generic parameter")
+	}
+	rt := rtPtr.Elem()
+
+	opts := mutationOptions{}
+	for _, opt := range options {
+		opt(&opts)
+	}
+
+	wrapped := func(g *CartGrain, m interface{}) error {
+		typed, ok := m.(*T)
+		if !ok {
+			return fmt.Errorf("mutation type mismatch: have %T want *%s", m, rt.Name())
+		}
+		return handler(g, typed)
+	}
+
+	mutationRegistryMu.Lock()
+	defer mutationRegistryMu.Unlock()
+
+	if _, exists := mutationRegistry[rt]; exists {
+		panic(fmt.Sprintf("RegisterMutation: duplicate registration for type %s", rt.String()))
+	}
+
+	mutationRegistry[rt] = &registeredMutation{
+		name:         name,
+		handler:      wrapped,
+		updateTotals: opts.updateTotals,
+		msgType:      rt,
+	}
+}
+
+// ApplyRegistered attempts to apply a registered mutation.
+// Returns updated grain if successful.
+//
+// If the mutation is not registered, returns (nil, ErrMutationNotRegistered).
+func ApplyRegistered(grain *CartGrain, msg interface{}) (*CartGrain, error) {
+	if grain == nil {
+		return nil, fmt.Errorf("nil grain")
+	}
+	if msg == nil {
+		return nil, fmt.Errorf("nil mutation message")
+	}
+
+	rt := indirectType(reflect.TypeOf(msg))
+	mutationRegistryMu.RLock()
+	entry, ok := mutationRegistry[rt]
+	mutationRegistryMu.RUnlock()
+
+	if !ok {
+		return nil, ErrMutationNotRegistered
+	}
+
+	if err := entry.handler(grain, msg); err != nil {
+		return nil, err
+	}
+
+	if entry.updateTotals {
+		grain.UpdateTotals()
+	}
+
+	return grain, nil
+}
+
+// RegisteredMutations returns metadata for all registered mutations (snapshot).
+func RegisteredMutations() []string {
+	mutationRegistryMu.RLock()
+	defer mutationRegistryMu.RUnlock()
+	out := make([]string, 0, len(mutationRegistry))
+	for _, entry := range mutationRegistry {
+		out = append(out, entry.name)
+	}
+	return out
+}
+
+// RegisteredMutationTypes returns the reflect.Type list of all registered messages.
+// Useful for coverage tests ensuring expected set matches actual set.
+func RegisteredMutationTypes() []reflect.Type {
+	mutationRegistryMu.RLock()
+	defer mutationRegistryMu.RUnlock()
+	out := make([]reflect.Type, 0, len(mutationRegistry))
+	for t := range mutationRegistry {
+		out = append(out, t)
+	}
+	return out
+}
+
+// MustAssertMutationCoverage can be called at startup to ensure every expected
+// mutation type has been registered. It panics with a descriptive message if any
+// are missing. Provide a slice of prototype pointers (e.g. []*messages.AddItem{nil} ...)
+func MustAssertMutationCoverage(expected []interface{}) {
+	mutationRegistryMu.RLock()
+	defer mutationRegistryMu.RUnlock()
+
+	missing := make([]string, 0)
+	for _, ex := range expected {
+		if ex == nil {
+			continue
+		}
+		t := indirectType(reflect.TypeOf(ex))
+		if _, ok := mutationRegistry[t]; !ok {
+			missing = append(missing, t.String())
+		}
+	}
+	if len(missing) > 0 {
+		panic(fmt.Sprintf("mutation registry missing handlers for: %v", missing))
+	}
+}
+
+// indirectType returns the element type if given a pointer; otherwise the type itself.
+func indirectType(t reflect.Type) reflect.Type {
+	for t.Kind() == reflect.Ptr {
+		t = t.Elem()
+	}
+	return t
+}
+
+/*
+Integration Guide
+-----------------
+
+1. Register all existing mutations:
+
+   func init() {
+       RegisterMutation[*messages.AddItem]("AddItem",
+           func(g *CartGrain, m *messages.AddItem) error {
+               // (port logic from existing switch branch)
+               // ...
+               return nil
+           },
+           WithTotals(),
+       )
+       // ... repeat for others
+   }
+
+2. In CartGrain.Apply (early in the method) add:
+
+   if updated, err := ApplyRegistered(c, content); err == nil {
+       return updated, nil
+   } else if err != ErrMutationNotRegistered {
+       return nil, err
+   }
+
+   // existing switch fallback below
+
+3. Once all mutations are registered, remove the legacy switch cases
+   and leave a single ErrMutationNotRegistered path for unknown types.
+
+4. Add a coverage test (see docs for example; removed from source for clarity).
+5. (Optional) Add metrics / tracing wrappers for handlers.
+
+*/

mutation_remove_delivery.go

@@ -0,0 +1,53 @@
+package main
+
+import (
+	"fmt"
+
+	messages "git.tornberg.me/go-cart-actor/proto"
+)
+
+// mutation_remove_delivery.go
+//
+// Registers the RemoveDelivery mutation.
+//
+// Behavior:
+//   - Removes the delivery entry whose Id == payload.Id.
+//   - If not found, returns an error.
+//   - Cart totals are recalculated (WithTotals) after removal.
+//   - Items previously associated with that delivery simply become "without delivery";
+//     subsequent delivery mutations can reassign them.
+//
+// Differences vs legacy:
+//   - Legacy logic decremented TotalPrice explicitly before recalculating.
+//     Here we rely solely on UpdateTotals() to recompute from remaining
+//     deliveries and items (simpler / single source of truth).
+//
+// Future considerations:
+//   - If delivery pricing logic changes (e.g., dynamic taxes per delivery),
+//     UpdateTotals() may need enhancement to incorporate delivery tax properly.
+func init() {
+	RegisterMutation[messages.RemoveDelivery](
+		"RemoveDelivery",
+		func(g *CartGrain, m *messages.RemoveDelivery) error {
+			if m == nil {
+				return fmt.Errorf("RemoveDelivery: nil payload")
+			}
+			targetID := int(m.Id)
+			index := -1
+			for i, d := range g.Deliveries {
+				if d.Id == targetID {
+					index = i
+					break
+				}
+			}
+			if index == -1 {
+				return fmt.Errorf("RemoveDelivery: delivery id %d not found", m.Id)
+			}
+
+			// Remove delivery (order not preserved beyond necessity)
+			g.Deliveries = append(g.Deliveries[:index], g.Deliveries[index+1:]...)
+			return nil
+		},
+		WithTotals(),
+	)
+}

mutation_remove_item.go

@@ -0,0 +1,49 @@
+package main
+
+import (
+	"fmt"
+
+	messages "git.tornberg.me/go-cart-actor/proto"
+)
+
+// mutation_remove_item.go
+//
+// Registers the RemoveItem mutation.
+//
+// Behavior:
+//   - Removes the cart line whose local cart line Id == payload.Id
+//   - If no such line exists returns an error
+//   - Recalculates cart totals (WithTotals)
+//
+// Notes:
+//   - This removes only the line item; any deliveries referencing the removed
+//     item are NOT automatically adjusted (mirrors prior logic). If future
+//     semantics require pruning delivery.item_ids you can extend this handler.
+//   - If multiple lines somehow shared the same Id (should not happen), only
+//     the first match would be removed—data integrity relies on unique line Ids.
+func init() {
+	RegisterMutation[messages.RemoveItem](
+		"RemoveItem",
+		func(g *CartGrain, m *messages.RemoveItem) error {
+			if m == nil {
+				return fmt.Errorf("RemoveItem: nil payload")
+			}
+			targetID := int(m.Id)
+
+			index := -1
+			for i, it := range g.Items {
+				if it.Id == targetID {
+					index = i
+					break
+				}
+			}
+			if index == -1 {
+				return fmt.Errorf("RemoveItem: item id %d not found", m.Id)
+			}
+
+			g.Items = append(g.Items[:index], g.Items[index+1:]...)
+			return nil
+		},
+		WithTotals(),
+	)
+}

mutation_set_cart_items.go

@@ -0,0 +1,57 @@
+package main
+
+import (
+	"fmt"
+
+	messages "git.tornberg.me/go-cart-actor/proto"
+)
+
+// mutation_set_cart_items.go
+//
+// Registers the SetCartRequest mutation. This mutation replaces the entire list
+// of cart items with the provided list (each entry is an AddRequest).
+//
+// Behavior:
+//   - Clears existing items (but leaves deliveries intact).
+//   - Iterates over each AddRequest and delegates to CartGrain.AddItem
+//     (which performs product lookup, creates AddItem mutation).
+//   - If any single addition fails, the mutation aborts with an error;
+//     items added prior to the failure remain (consistent with previous behavior).
+//   - Totals recalculated after completion via WithTotals().
+//
+// Notes:
+//   - Potential optimization: batch product lookups; currently sequential.
+//   - Consider adding rollback semantics if atomic replacement is desired.
+//   - Deliveries might reference item IDs that are now invalid—original logic
+//     also left deliveries untouched. If that becomes an issue, add a cleanup
+//     pass to remove deliveries whose item IDs no longer exist.
+func init() {
+	RegisterMutation[messages.SetCartRequest](
+		"SetCartRequest",
+		func(g *CartGrain, m *messages.SetCartRequest) error {
+			if m == nil {
+				return fmt.Errorf("SetCartRequest: nil payload")
+			}
+
+			// Clear current items (keep deliveries)
+			g.mu.Lock()
+			g.Items = make([]*CartItem, 0, len(m.Items))
+			g.mu.Unlock()
+
+			for _, it := range m.Items {
+				if it == nil {
+					continue
+				}
+				if it.Sku == "" || it.Quantity < 1 {
+					return fmt.Errorf("SetCartRequest: invalid item (sku='%s' qty=%d)", it.Sku, it.Quantity)
+				}
+				_, err := g.AddItem(it.Sku, int(it.Quantity), it.Country, it.StoreId)
+				if err != nil {
+					return fmt.Errorf("SetCartRequest: add sku '%s' failed: %w", it.Sku, err)
+				}
+			}
+			return nil
+		},
+		WithTotals(),
+	)
+}

mutation_set_delivery.go

@@ -0,0 +1,101 @@
+package main
+
+import (
+	"fmt"
+	"slices"
+
+	messages "git.tornberg.me/go-cart-actor/proto"
+)
+
+// mutation_set_delivery.go
+//
+// Registers the SetDelivery mutation.
+//
+// Semantics (mirrors legacy switch logic):
+//   - If the payload specifies an explicit list of item IDs (payload.Items):
+//   - Each referenced cart line must exist.
+//   - None of the referenced items may already belong to a delivery.
+//   - Only those items are associated with the new delivery.
+//   - If payload.Items is empty:
+//   - All items currently without any delivery are associated with the new delivery.
+//   - A new delivery line is created with:
+//   - Auto-incremented delivery ID (cart-local)
+//   - Provider from payload
+//   - Fixed price (currently hard-coded: 4900 minor units) – adjust as needed
+//   - Optional PickupPoint copied from payload
+//   - Cart totals are recalculated (WithTotals)
+//
+// Error cases:
+//   - Referenced item does not exist
+//   - Referenced item already has a delivery
+//   - No items qualify (resulting association set empty) -> returns error (prevents creating empty delivery)
+//
+// Concurrency:
+//   - Uses g.mu to protect lastDeliveryId increment and append to Deliveries slice.
+//     Item scans are read-only and performed outside the lock for simplicity;
+//     if stricter guarantees are needed, widen the lock section.
+//
+// Future extension points:
+//   - Variable delivery pricing (based on weight, distance, provider, etc.)
+//   - Validation of provider codes
+//   - Multi-currency delivery pricing
+func init() {
+	RegisterMutation[messages.SetDelivery](
+		"SetDelivery",
+		func(g *CartGrain, m *messages.SetDelivery) error {
+			if m == nil {
+				return fmt.Errorf("SetDelivery: nil payload")
+			}
+			if m.Provider == "" {
+				return fmt.Errorf("SetDelivery: provider is empty")
+			}
+
+			withDelivery := g.ItemsWithDelivery()
+			targetItems := make([]int, 0)
+
+			if len(m.Items) == 0 {
+				// Use every item currently without a delivery
+				targetItems = append(targetItems, g.ItemsWithoutDelivery()...)
+			} else {
+				// Validate explicit list
+				for _, id64 := range m.Items {
+					id := int(id64)
+					found := false
+					for _, it := range g.Items {
+						if it.Id == id {
+							found = true
+							break
+						}
+					}
+					if !found {
+						return fmt.Errorf("SetDelivery: item id %d not found", id)
+					}
+					if slices.Contains(withDelivery, id) {
+						return fmt.Errorf("SetDelivery: item id %d already has a delivery", id)
+					}
+					targetItems = append(targetItems, id)
+				}
+			}
+
+			if len(targetItems) == 0 {
+				return fmt.Errorf("SetDelivery: no eligible items to attach")
+			}
+
+			// Append new delivery
+			g.mu.Lock()
+			g.lastDeliveryId++
+			newId := g.lastDeliveryId
+			g.Deliveries = append(g.Deliveries, &CartDelivery{
+				Id:          newId,
+				Provider:    m.Provider,
+				PickupPoint: m.PickupPoint,
+				Price:       4900, // TODO: externalize pricing
+				Items:       targetItems,
+			})
+			g.mu.Unlock()
+
+			return nil
+		},
+		WithTotals(),
+	)
+}

mutation_set_pickup_point.go

@@ -0,0 +1,56 @@
+package main
+
+import (
+	"fmt"
+
+	messages "git.tornberg.me/go-cart-actor/proto"
+)
+
+// mutation_set_pickup_point.go
+//
+// Registers the SetPickupPoint mutation using the generic mutation registry.
+//
+// Semantics (mirrors original switch-based implementation):
+//   - Locate the delivery with Id == payload.DeliveryId
+//   - Set (or overwrite) its PickupPoint with the provided data
+//   - Does NOT alter pricing or taxes (so no totals recalculation required)
+//
+// Validation / Error Handling:
+//   - If payload is nil -> error
+//   - If DeliveryId not found -> error
+//
+// Concurrency:
+//   - Relies on the existing expectation that higher-level mutation routing
+//     serializes Apply() calls per grain; if stricter guarantees are needed,
+//     a delivery-level lock could be introduced later.
+//
+// Future Extensions:
+//   - Validate pickup point fields (country code, zip format, etc.)
+//   - Track history / audit of pickup point changes
+//   - Trigger delivery price adjustments (which would then require WithTotals()).
+func init() {
+	RegisterMutation[messages.SetPickupPoint](
+		"SetPickupPoint",
+		func(g *CartGrain, m *messages.SetPickupPoint) error {
+			if m == nil {
+				return fmt.Errorf("SetPickupPoint: nil payload")
+			}
+
+			for _, d := range g.Deliveries {
+				if d.Id == int(m.DeliveryId) {
+					d.PickupPoint = &messages.PickupPoint{
+						Id:      m.Id,
+						Name:    m.Name,
+						Address: m.Address,
+						City:    m.City,
+						Zip:     m.Zip,
+						Country: m.Country,
+					}
+					return nil
+				}
+			}
+			return fmt.Errorf("SetPickupPoint: delivery id %d not found", m.DeliveryId)
+		},
+		// No WithTotals(): pickup point does not change pricing / tax.
+	)
+}

pool-server.go

@@ -1,10 +1,10 @@
 package main
 
 import (
+	"bytes"
 	"encoding/json"
 	"fmt"
 	"log"
-	"math/rand"
 	"net/http"
 	"strconv"
 	"time"
@@ -24,21 +24,26 @@ func NewPoolServer(pool GrainPool, pod_name string) *PoolServer {
 	}
 }
 
+func (s *PoolServer) process(id CartId, mutation interface{}) (*CartGrain, error) {
+	grain, err := s.pool.Apply(id, mutation)
+	if err != nil {
+		return nil, err
+	}
+	return grain, nil
+}
+
 func (s *PoolServer) HandleGet(w http.ResponseWriter, r *http.Request, id CartId) error {
-	data, err := s.pool.Get(id)
+	grain, err := s.pool.Get(id)
 	if err != nil {
 		return err
 	}
 
-	return s.WriteResult(w, data)
+	return s.WriteResult(w, grain)
 }
 
 func (s *PoolServer) HandleAddSku(w http.ResponseWriter, r *http.Request, id CartId) error {
 	sku := r.PathValue("sku")
-	data, err := s.pool.Process(id, Message{
-		Type:    AddRequestType,
-		Content: &messages.AddRequest{Sku: sku, Quantity: 1},
-	})
+	data, err := s.process(id, &messages.AddRequest{Sku: sku, Quantity: 1})
 	if err != nil {
 		return err
 	}
@@ -56,23 +61,20 @@ func ErrorHandler(fn func(w http.ResponseWriter, r *http.Request) error) func(w
 	}
 }
 
-func (s *PoolServer) WriteResult(w http.ResponseWriter, result *FrameWithPayload) error {
+func (s *PoolServer) WriteResult(w http.ResponseWriter, result *CartGrain) error {
 	w.Header().Set("Content-Type", "application/json")
 	w.Header().Set("Cache-Control", "no-cache")
 	w.Header().Set("Access-Control-Allow-Origin", "*")
 	w.Header().Set("X-Pod-Name", s.pod_name)
-	if result.StatusCode != 200 {
-		log.Printf("Call error: %d\n", result.StatusCode)
-		if result.StatusCode >= 200 && result.StatusCode < 600 {
-			w.WriteHeader(int(result.StatusCode))
-		} else {
-			w.WriteHeader(http.StatusInternalServerError)
-		}
-		w.Write([]byte(result.Payload))
+	if result == nil {
+
+		w.WriteHeader(http.StatusInternalServerError)
+
 		return nil
 	}
 	w.WriteHeader(http.StatusOK)
-	_, err := w.Write(result.Payload)
+	enc := json.NewEncoder(w)
+	err := enc.Encode(result)
 	return err
 }
 
@@ -83,10 +85,7 @@ func (s *PoolServer) HandleDeleteItem(w http.ResponseWriter, r *http.Request, id
 	if err != nil {
 		return err
 	}
-	data, err := s.pool.Process(id, Message{
-		Type:    RemoveItemType,
-		Content: &messages.RemoveItem{Id: int64(itemId)},
-	})
+	data, err := s.process(id, &messages.RemoveItem{Id: int64(itemId)})
 	if err != nil {
 		return err
 	}
@@ -106,13 +105,10 @@ func (s *PoolServer) HandleSetDelivery(w http.ResponseWriter, r *http.Request, i
 	if err != nil {
 		return err
 	}
-	data, err := s.pool.Process(id, Message{
-		Type: SetDeliveryType,
-		Content: &messages.SetDelivery{
-			Provider:    delivery.Provider,
-			Items:       delivery.Items,
-			PickupPoint: delivery.PickupPoint,
-		},
+	data, err := s.process(id, &messages.SetDelivery{
+		Provider:    delivery.Provider,
+		Items:       delivery.Items,
+		PickupPoint: delivery.PickupPoint,
 	})
 	if err != nil {
 		return err
@@ -132,17 +128,14 @@ func (s *PoolServer) HandleSetPickupPoint(w http.ResponseWriter, r *http.Request
 	if err != nil {
 		return err
 	}
-	reply, err := s.pool.Process(id, Message{
-		Type: SetPickupPointType,
-		Content: &messages.SetPickupPoint{
-			DeliveryId: int64(deliveryId),
-			Id:         pickupPoint.Id,
-			Name:       pickupPoint.Name,
-			Address:    pickupPoint.Address,
-			City:       pickupPoint.City,
-			Zip:        pickupPoint.Zip,
-			Country:    pickupPoint.Country,
-		},
+	reply, err := s.process(id, &messages.SetPickupPoint{
+		DeliveryId: int64(deliveryId),
+		Id:         pickupPoint.Id,
+		Name:       pickupPoint.Name,
+		Address:    pickupPoint.Address,
+		City:       pickupPoint.City,
+		Zip:        pickupPoint.Zip,
+		Country:    pickupPoint.Country,
 	})
 	if err != nil {
 		return err
@@ -157,10 +150,7 @@ func (s *PoolServer) HandleRemoveDelivery(w http.ResponseWriter, r *http.Request
 	if err != nil {
 		return err
 	}
-	reply, err := s.pool.Process(id, Message{
-		Type:    RemoveDeliveryType,
-		Content: &messages.RemoveDelivery{Id: int64(deliveryId)},
-	})
+	reply, err := s.process(id, &messages.RemoveDelivery{Id: int64(deliveryId)})
 	if err != nil {
 		return err
 	}
@@ -173,10 +163,7 @@ func (s *PoolServer) HandleQuantityChange(w http.ResponseWriter, r *http.Request
 	if err != nil {
 		return err
 	}
-	reply, err := s.pool.Process(id, Message{
-		Type:    ChangeQuantityType,
-		Content: &changeQuantity,
-	})
+	reply, err := s.process(id, &changeQuantity)
 	if err != nil {
 		return err
 	}
@@ -189,10 +176,7 @@ func (s *PoolServer) HandleSetCartItems(w http.ResponseWriter, r *http.Request,
 	if err != nil {
 		return err
 	}
-	reply, err := s.pool.Process(id, Message{
-		Type:    SetCartItemsType,
-		Content: &setCartItems,
-	})
+	reply, err := s.process(id, &setCartItems)
 	if err != nil {
 		return err
 	}
@@ -205,10 +189,7 @@ func (s *PoolServer) HandleAddRequest(w http.ResponseWriter, r *http.Request, id
 	if err != nil {
 		return err
 	}
-	reply, err := s.pool.Process(id, Message{
-		Type:    AddRequestType,
-		Content: &addRequest,
-	})
+	reply, err := s.process(id, &addRequest)
 	if err != nil {
 		return err
 	}
@@ -234,68 +215,104 @@ func (s *PoolServer) HandleConfirmation(w http.ResponseWriter, r *http.Request,
 	return json.NewEncoder(w).Encode(order)
 }
 
-func (s *PoolServer) HandleCheckout(w http.ResponseWriter, r *http.Request, id CartId) error {
+func (s *PoolServer) CreateOrUpdateCheckout(host string, id CartId) (*CheckoutOrder, error) {
+	meta := &CheckoutMeta{
+		Terms:        fmt.Sprintf("https://%s/terms", host),
+		Checkout:     fmt.Sprintf("https://%s/checkout?order_id={checkout.order.id}", host),
+		Confirmation: fmt.Sprintf("https://%s/confirmation/{checkout.order.id}", host),
+		Validation:   fmt.Sprintf("https://%s/validate", host),
+		Push:         fmt.Sprintf("https://%s/push?order_id={checkout.order.id}", host),
+		Country:      getCountryFromHost(host),
+	}
 
-	reply, err := s.pool.Process(id, Message{
-		Type: CreateCheckoutOrderType,
-		Content: &messages.CreateCheckoutOrder{
-			Terms:        "https://slask-finder.tornberg.me/terms",
-			Checkout:     "https://slask-finder.tornberg.me/checkout?order_id={checkout.order.id}",
-			Confirmation: "https://slask-finder.tornberg.me/confirmation/{checkout.order.id}",
-			Push:         "https://cart.tornberg.me/push?order_id={checkout.order.id}",
-		},
+	// Get current grain state (may be local or remote)
+	grain, err := s.pool.Get(id)
+	if err != nil {
+		return nil, err
+	}
+
+	// Build pure checkout payload
+	payload, _, err := BuildCheckoutOrderPayload(grain, meta)
+	if err != nil {
+		return nil, err
+	}
+
+	if grain.OrderReference != "" {
+		return KlarnaInstance.UpdateOrder(grain.OrderReference, bytes.NewReader(payload))
+	} else {
+		return KlarnaInstance.CreateOrder(bytes.NewReader(payload))
+	}
+}
+
+func (s *PoolServer) ApplyCheckoutStarted(klarnaOrder *CheckoutOrder, id CartId) (*CartGrain, error) {
+	// Persist initialization state via mutation (best-effort)
+	return s.pool.Apply(id, &messages.InitializeCheckout{
+		OrderId:           klarnaOrder.ID,
+		Status:            klarnaOrder.Status,
+		PaymentInProgress: true,
 	})
+}
+
+func (s *PoolServer) HandleCheckout(w http.ResponseWriter, r *http.Request, id CartId) error {
+	klarnaOrder, err := s.CreateOrUpdateCheckout(r.Host, id)
 	if err != nil {
 		return err
 	}
-	if reply.StatusCode != 200 {
-		return s.WriteResult(w, reply)
-	}
 
-	// w.Header().Set("Content-Type", "application/json")
-	// w.Header().Set("X-Pod-Name", s.pod_name)
-	// w.Header().Set("Cache-Control", "no-cache")
-	// w.Header().Set("Access-Control-Allow-Origin", "*")
-	// w.WriteHeader(http.StatusOK)
+	s.ApplyCheckoutStarted(klarnaOrder, id)
 
-	return s.WriteResult(w, reply)
+	w.Header().Set("Content-Type", "application/json")
+	return json.NewEncoder(w).Encode(klarnaOrder)
 }
 
-func NewCartId() CartId {
-	id := time.Now().UnixNano() + rand.Int63()
-
-	return ToCartId(fmt.Sprintf("%d", id))
-}
-
-func CookieCartIdHandler(fn func(w http.ResponseWriter, r *http.Request, cartId CartId) error) func(w http.ResponseWriter, r *http.Request) error {
+func CookieCartIdHandler(fn func(cartId CartId, w http.ResponseWriter, r *http.Request) error) func(w http.ResponseWriter, r *http.Request) error {
 	return func(w http.ResponseWriter, r *http.Request) error {
-		var cartId CartId
-		cartIdCookie := r.CookiesNamed("cartid")
-		if cartIdCookie == nil || len(cartIdCookie) == 0 {
-			cartId = NewCartId()
+		var id CartId
+		cookie, err := r.Cookie("cartid")
+		if err != nil || cookie.Value == "" {
+			id = MustNewCartId()
 			http.SetCookie(w, &http.Cookie{
 				Name:     "cartid",
-				Value:    cartId.String(),
-				Secure:   true,
+				Value:    id.String(),
+				Secure:   r.TLS != nil,
 				HttpOnly: true,
 				Path:     "/",
 				Expires:  time.Now().AddDate(0, 0, 14),
 				SameSite: http.SameSiteLaxMode,
 			})
+			w.Header().Set("Set-Cart-Id", id.String())
 		} else {
-			cartId = ToCartId(cartIdCookie[0].Value)
+			parsed, ok := ParseCartId(cookie.Value)
+			if !ok {
+				id = MustNewCartId()
+				http.SetCookie(w, &http.Cookie{
+					Name:     "cartid",
+					Value:    id.String(),
+					Secure:   r.TLS != nil,
+					HttpOnly: true,
+					Path:     "/",
+					Expires:  time.Now().AddDate(0, 0, 14),
+					SameSite: http.SameSiteLaxMode,
+				})
+				w.Header().Set("Set-Cart-Id", id.String())
+			} else {
+				id = parsed
+			}
 		}
-		return fn(w, r, cartId)
+
+		return fn(id, w, r)
 	}
 }
 
+// Removed leftover legacy block after CookieCartIdHandler (obsolete code referencing cid/legacy)
+
 func (s *PoolServer) RemoveCartCookie(w http.ResponseWriter, r *http.Request, cartId CartId) error {
-	cartId = NewCartId()
+	// Clear cart cookie (breaking change: do not issue a new legacy id here)
 	http.SetCookie(w, &http.Cookie{
 		Name:     "cartid",
-		Value:    cartId.String(),
+		Value:    "",
 		Path:     "/",
-		Secure:   true,
+		Secure:   r.TLS != nil,
 		HttpOnly: true,
 		Expires:  time.Unix(0, 0),
 		SameSite: http.SameSiteLaxMode,
@@ -304,16 +321,47 @@ func (s *PoolServer) RemoveCartCookie(w http.ResponseWriter, r *http.Request, ca
 	return nil
 }
 
-func CartIdHandler(fn func(w http.ResponseWriter, r *http.Request, cartId CartId) error) func(w http.ResponseWriter, r *http.Request) error {
+func CartIdHandler(fn func(cartId CartId, w http.ResponseWriter, r *http.Request) error) func(w http.ResponseWriter, r *http.Request) error {
 	return func(w http.ResponseWriter, r *http.Request) error {
-		cartId := ToCartId(r.PathValue("id"))
+		raw := r.PathValue("id")
+		// If no id supplied, generate a new one
+		if raw == "" {
+			id := MustNewCartId()
+			w.Header().Set("Set-Cart-Id", id.String())
+
+			return fn(id, w, r)
+		}
+		// Parse base62 cart id
+		id, ok := ParseCartId(raw)
+		if !ok {
+			return fmt.Errorf("invalid cart id format")
+		}
+
+		return fn(id, w, r)
+	}
+}
+
+func (s *PoolServer) ProxyHandler(fn func(w http.ResponseWriter, r *http.Request, cartId CartId) error) func(cartId CartId, w http.ResponseWriter, r *http.Request) error {
+	return func(cartId CartId, w http.ResponseWriter, r *http.Request) error {
+		if ownerHost, ok := s.pool.OwnerHost(cartId); ok {
+			handled, err := ownerHost.Proxy(cartId, w, r)
+			if err != nil {
+				log.Printf("proxy failed: %v, taking ownership", err)
+				s.pool.TakeOwnership(cartId)
+			} else if handled {
+				return nil
+			}
+		}
+		// Local ownership or no owner known, proceed with local handling
+
 		return fn(w, r, cartId)
+
 	}
 }
 
 func (s *PoolServer) Serve() *http.ServeMux {
+
 	mux := http.NewServeMux()
-	//mux.HandleFunc("/", s.RewritePath)
 	mux.HandleFunc("OPTIONS /", func(w http.ResponseWriter, r *http.Request) {
 		w.Header().Set("Access-Control-Allow-Origin", "*")
 		w.Header().Set("Access-Control-Allow-Methods", "GET, PUT, POST, DELETE")
@@ -321,29 +369,29 @@ func (s *PoolServer) Serve() *http.ServeMux {
 		w.WriteHeader(http.StatusOK)
 	})
 
-	mux.HandleFunc("GET /", ErrorHandler(CookieCartIdHandler(s.HandleGet)))
-	mux.HandleFunc("GET /add/{sku}", ErrorHandler(CookieCartIdHandler(s.HandleAddSku)))
-	mux.HandleFunc("POST /", ErrorHandler(CookieCartIdHandler(s.HandleAddRequest)))
-	mux.HandleFunc("POST /set", ErrorHandler(CookieCartIdHandler(s.HandleSetCartItems)))
-	mux.HandleFunc("DELETE /{itemId}", ErrorHandler(CookieCartIdHandler(s.HandleDeleteItem)))
-	mux.HandleFunc("PUT /", ErrorHandler(CookieCartIdHandler(s.HandleQuantityChange)))
-	mux.HandleFunc("DELETE /", ErrorHandler(CookieCartIdHandler(s.RemoveCartCookie)))
-	mux.HandleFunc("POST /delivery", ErrorHandler(CookieCartIdHandler(s.HandleSetDelivery)))
-	mux.HandleFunc("DELETE /delivery/{deliveryId}", ErrorHandler(CookieCartIdHandler(s.HandleRemoveDelivery)))
-	mux.HandleFunc("PUT /delivery/{deliveryId}/pickupPoint", ErrorHandler(CookieCartIdHandler(s.HandleSetPickupPoint)))
-	mux.HandleFunc("GET /checkout", ErrorHandler(CookieCartIdHandler(s.HandleCheckout)))
-	mux.HandleFunc("GET /confirmation/{orderId}", ErrorHandler(CookieCartIdHandler(s.HandleConfirmation)))
+	mux.HandleFunc("GET /", ErrorHandler(CookieCartIdHandler(s.ProxyHandler(s.HandleGet))))
+	mux.HandleFunc("GET /add/{sku}", ErrorHandler(CookieCartIdHandler(s.ProxyHandler(s.HandleAddSku))))
+	mux.HandleFunc("POST /", ErrorHandler(CookieCartIdHandler(s.ProxyHandler(s.HandleAddRequest))))
+	mux.HandleFunc("POST /set", ErrorHandler(CookieCartIdHandler(s.ProxyHandler(s.HandleSetCartItems))))
+	mux.HandleFunc("DELETE /{itemId}", ErrorHandler(CookieCartIdHandler(s.ProxyHandler(s.HandleDeleteItem))))
+	mux.HandleFunc("PUT /", ErrorHandler(CookieCartIdHandler(s.ProxyHandler(s.HandleQuantityChange))))
+	mux.HandleFunc("DELETE /", ErrorHandler(CookieCartIdHandler(s.ProxyHandler(s.RemoveCartCookie))))
+	mux.HandleFunc("POST /delivery", ErrorHandler(CookieCartIdHandler(s.ProxyHandler(s.HandleSetDelivery))))
+	mux.HandleFunc("DELETE /delivery/{deliveryId}", ErrorHandler(CookieCartIdHandler(s.ProxyHandler(s.HandleRemoveDelivery))))
+	mux.HandleFunc("PUT /delivery/{deliveryId}/pickupPoint", ErrorHandler(CookieCartIdHandler(s.ProxyHandler(s.HandleSetPickupPoint))))
+	mux.HandleFunc("GET /checkout", ErrorHandler(CookieCartIdHandler(s.ProxyHandler(s.HandleCheckout))))
+	mux.HandleFunc("GET /confirmation/{orderId}", ErrorHandler(CookieCartIdHandler(s.ProxyHandler(s.HandleConfirmation))))
 
-	mux.HandleFunc("GET /byid/{id}", ErrorHandler(CartIdHandler(s.HandleGet)))
-	mux.HandleFunc("GET /byid/{id}/add/{sku}", ErrorHandler(CartIdHandler(s.HandleAddSku)))
-	mux.HandleFunc("POST /byid/{id}", ErrorHandler(CartIdHandler(s.HandleAddRequest)))
-	mux.HandleFunc("DELETE /byid/{id}/{itemId}", ErrorHandler(CartIdHandler(s.HandleDeleteItem)))
-	mux.HandleFunc("PUT /byid/{id}", ErrorHandler(CartIdHandler(s.HandleQuantityChange)))
-	mux.HandleFunc("POST /byid/{id}/delivery", ErrorHandler(CartIdHandler(s.HandleSetDelivery)))
-	mux.HandleFunc("DELETE /byid/{id}/delivery/{deliveryId}", ErrorHandler(CartIdHandler(s.HandleRemoveDelivery)))
-	mux.HandleFunc("PUT /byid/{id}/delivery/{deliveryId}/pickupPoint", ErrorHandler(CartIdHandler(s.HandleSetPickupPoint)))
-	mux.HandleFunc("GET /byid/{id}/checkout", ErrorHandler(CartIdHandler(s.HandleCheckout)))
-	mux.HandleFunc("GET /byid/{id}/confirmation", ErrorHandler(CartIdHandler(s.HandleConfirmation)))
+	mux.HandleFunc("GET /byid/{id}", ErrorHandler(CartIdHandler(s.ProxyHandler(s.HandleGet))))
+	mux.HandleFunc("GET /byid/{id}/add/{sku}", ErrorHandler(CartIdHandler(s.ProxyHandler(s.HandleAddSku))))
+	mux.HandleFunc("POST /byid/{id}", ErrorHandler(CartIdHandler(s.ProxyHandler(s.HandleAddRequest))))
+	mux.HandleFunc("DELETE /byid/{id}/{itemId}", ErrorHandler(CartIdHandler(s.ProxyHandler(s.HandleDeleteItem))))
+	mux.HandleFunc("PUT /byid/{id}", ErrorHandler(CartIdHandler(s.ProxyHandler(s.HandleQuantityChange))))
+	mux.HandleFunc("POST /byid/{id}/delivery", ErrorHandler(CartIdHandler(s.ProxyHandler(s.HandleSetDelivery))))
+	mux.HandleFunc("DELETE /byid/{id}/delivery/{deliveryId}", ErrorHandler(CartIdHandler(s.ProxyHandler(s.HandleRemoveDelivery))))
+	mux.HandleFunc("PUT /byid/{id}/delivery/{deliveryId}/pickupPoint", ErrorHandler(CartIdHandler(s.ProxyHandler(s.HandleSetPickupPoint))))
+	mux.HandleFunc("GET /byid/{id}/checkout", ErrorHandler(CartIdHandler(s.ProxyHandler(s.HandleCheckout))))
+	mux.HandleFunc("GET /byid/{id}/confirmation", ErrorHandler(CartIdHandler(s.ProxyHandler(s.HandleConfirmation))))
 
 	return mux
 }

proto/cart_actor.pb.go

@@ -1,420 +0,0 @@
-// Code generated by protoc-gen-go. DO NOT EDIT.
-// versions:
-// 	protoc-gen-go v1.36.10
-// 	protoc        v3.21.12
-// source: cart_actor.proto
-
-package messages
-
-import (
-	protoreflect "google.golang.org/protobuf/reflect/protoreflect"
-	protoimpl "google.golang.org/protobuf/runtime/protoimpl"
-	reflect "reflect"
-	sync "sync"
-	unsafe "unsafe"
-)
-
-const (
-	// Verify that this generated code is sufficiently up-to-date.
-	_ = protoimpl.EnforceVersion(20 - protoimpl.MinVersion)
-	// Verify that runtime/protoimpl is sufficiently up-to-date.
-	_ = protoimpl.EnforceVersion(protoimpl.MaxVersion - 20)
-)
-
-// MutationType corresponds 1:1 with the legacy uint16 message type constants.
-type MutationType int32
-
-const (
-	MutationType_MUTATION_TYPE_UNSPECIFIED MutationType = 0
-	MutationType_MUTATION_ADD_REQUEST      MutationType = 1
-	MutationType_MUTATION_ADD_ITEM         MutationType = 2
-	// (3 was unused / reserved in legacy framing)
-	MutationType_MUTATION_REMOVE_ITEM           MutationType = 4
-	MutationType_MUTATION_REMOVE_DELIVERY       MutationType = 5
-	MutationType_MUTATION_CHANGE_QUANTITY       MutationType = 6
-	MutationType_MUTATION_SET_DELIVERY          MutationType = 7
-	MutationType_MUTATION_SET_PICKUP_POINT      MutationType = 8
-	MutationType_MUTATION_CREATE_CHECKOUT_ORDER MutationType = 9
-	MutationType_MUTATION_SET_CART_ITEMS        MutationType = 10
-	MutationType_MUTATION_ORDER_COMPLETED       MutationType = 11
-)
-
-// Enum value maps for MutationType.
-var (
-	MutationType_name = map[int32]string{
-		0:  "MUTATION_TYPE_UNSPECIFIED",
-		1:  "MUTATION_ADD_REQUEST",
-		2:  "MUTATION_ADD_ITEM",
-		4:  "MUTATION_REMOVE_ITEM",
-		5:  "MUTATION_REMOVE_DELIVERY",
-		6:  "MUTATION_CHANGE_QUANTITY",
-		7:  "MUTATION_SET_DELIVERY",
-		8:  "MUTATION_SET_PICKUP_POINT",
-		9:  "MUTATION_CREATE_CHECKOUT_ORDER",
-		10: "MUTATION_SET_CART_ITEMS",
-		11: "MUTATION_ORDER_COMPLETED",
-	}
-	MutationType_value = map[string]int32{
-		"MUTATION_TYPE_UNSPECIFIED":      0,
-		"MUTATION_ADD_REQUEST":           1,
-		"MUTATION_ADD_ITEM":              2,
-		"MUTATION_REMOVE_ITEM":           4,
-		"MUTATION_REMOVE_DELIVERY":       5,
-		"MUTATION_CHANGE_QUANTITY":       6,
-		"MUTATION_SET_DELIVERY":          7,
-		"MUTATION_SET_PICKUP_POINT":      8,
-		"MUTATION_CREATE_CHECKOUT_ORDER": 9,
-		"MUTATION_SET_CART_ITEMS":        10,
-		"MUTATION_ORDER_COMPLETED":       11,
-	}
-)
-
-func (x MutationType) Enum() *MutationType {
-	p := new(MutationType)
-	*p = x
-	return p
-}
-
-func (x MutationType) String() string {
-	return protoimpl.X.EnumStringOf(x.Descriptor(), protoreflect.EnumNumber(x))
-}
-
-func (MutationType) Descriptor() protoreflect.EnumDescriptor {
-	return file_cart_actor_proto_enumTypes[0].Descriptor()
-}
-
-func (MutationType) Type() protoreflect.EnumType {
-	return &file_cart_actor_proto_enumTypes[0]
-}
-
-func (x MutationType) Number() protoreflect.EnumNumber {
-	return protoreflect.EnumNumber(x)
-}
-
-// Deprecated: Use MutationType.Descriptor instead.
-func (MutationType) EnumDescriptor() ([]byte, []int) {
-	return file_cart_actor_proto_rawDescGZIP(), []int{0}
-}
-
-// MutationRequest is an envelope:
-// - cart_id: string form of CartId (legacy 16-byte array truncated/padded).
-// - type: mutation kind (see enum).
-// - payload: serialized underlying proto message (AddRequest, AddItem, etc.).
-// - client_timestamp: optional unix timestamp; server sets if zero.
-type MutationRequest struct {
-	state           protoimpl.MessageState `protogen:"open.v1"`
-	CartId          string                 `protobuf:"bytes,1,opt,name=cart_id,json=cartId,proto3" json:"cart_id,omitempty"`
-	Type            MutationType           `protobuf:"varint,2,opt,name=type,proto3,enum=messages.MutationType" json:"type,omitempty"`
-	Payload         []byte                 `protobuf:"bytes,3,opt,name=payload,proto3" json:"payload,omitempty"`
-	ClientTimestamp int64                  `protobuf:"varint,4,opt,name=client_timestamp,json=clientTimestamp,proto3" json:"client_timestamp,omitempty"`
-	unknownFields   protoimpl.UnknownFields
-	sizeCache       protoimpl.SizeCache
-}
-
-func (x *MutationRequest) Reset() {
-	*x = MutationRequest{}
-	mi := &file_cart_actor_proto_msgTypes[0]
-	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
-	ms.StoreMessageInfo(mi)
-}
-
-func (x *MutationRequest) String() string {
-	return protoimpl.X.MessageStringOf(x)
-}
-
-func (*MutationRequest) ProtoMessage() {}
-
-func (x *MutationRequest) ProtoReflect() protoreflect.Message {
-	mi := &file_cart_actor_proto_msgTypes[0]
-	if x != nil {
-		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
-		if ms.LoadMessageInfo() == nil {
-			ms.StoreMessageInfo(mi)
-		}
-		return ms
-	}
-	return mi.MessageOf(x)
-}
-
-// Deprecated: Use MutationRequest.ProtoReflect.Descriptor instead.
-func (*MutationRequest) Descriptor() ([]byte, []int) {
-	return file_cart_actor_proto_rawDescGZIP(), []int{0}
-}
-
-func (x *MutationRequest) GetCartId() string {
-	if x != nil {
-		return x.CartId
-	}
-	return ""
-}
-
-func (x *MutationRequest) GetType() MutationType {
-	if x != nil {
-		return x.Type
-	}
-	return MutationType_MUTATION_TYPE_UNSPECIFIED
-}
-
-func (x *MutationRequest) GetPayload() []byte {
-	if x != nil {
-		return x.Payload
-	}
-	return nil
-}
-
-func (x *MutationRequest) GetClientTimestamp() int64 {
-	if x != nil {
-		return x.ClientTimestamp
-	}
-	return 0
-}
-
-// MutationReply returns a status code (legacy semantics) plus a JSON payload
-// representing the full cart state (or an error message if non-200).
-type MutationReply struct {
-	state         protoimpl.MessageState `protogen:"open.v1"`
-	StatusCode    int32                  `protobuf:"varint,1,opt,name=status_code,json=statusCode,proto3" json:"status_code,omitempty"`
-	Payload       []byte                 `protobuf:"bytes,2,opt,name=payload,proto3" json:"payload,omitempty"` // JSON cart state or error string
-	unknownFields protoimpl.UnknownFields
-	sizeCache     protoimpl.SizeCache
-}
-
-func (x *MutationReply) Reset() {
-	*x = MutationReply{}
-	mi := &file_cart_actor_proto_msgTypes[1]
-	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
-	ms.StoreMessageInfo(mi)
-}
-
-func (x *MutationReply) String() string {
-	return protoimpl.X.MessageStringOf(x)
-}
-
-func (*MutationReply) ProtoMessage() {}
-
-func (x *MutationReply) ProtoReflect() protoreflect.Message {
-	mi := &file_cart_actor_proto_msgTypes[1]
-	if x != nil {
-		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
-		if ms.LoadMessageInfo() == nil {
-			ms.StoreMessageInfo(mi)
-		}
-		return ms
-	}
-	return mi.MessageOf(x)
-}
-
-// Deprecated: Use MutationReply.ProtoReflect.Descriptor instead.
-func (*MutationReply) Descriptor() ([]byte, []int) {
-	return file_cart_actor_proto_rawDescGZIP(), []int{1}
-}
-
-func (x *MutationReply) GetStatusCode() int32 {
-	if x != nil {
-		return x.StatusCode
-	}
-	return 0
-}
-
-func (x *MutationReply) GetPayload() []byte {
-	if x != nil {
-		return x.Payload
-	}
-	return nil
-}
-
-// StateRequest fetches current cart state without mutation.
-type StateRequest struct {
-	state         protoimpl.MessageState `protogen:"open.v1"`
-	CartId        string                 `protobuf:"bytes,1,opt,name=cart_id,json=cartId,proto3" json:"cart_id,omitempty"`
-	unknownFields protoimpl.UnknownFields
-	sizeCache     protoimpl.SizeCache
-}
-
-func (x *StateRequest) Reset() {
-	*x = StateRequest{}
-	mi := &file_cart_actor_proto_msgTypes[2]
-	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
-	ms.StoreMessageInfo(mi)
-}
-
-func (x *StateRequest) String() string {
-	return protoimpl.X.MessageStringOf(x)
-}
-
-func (*StateRequest) ProtoMessage() {}
-
-func (x *StateRequest) ProtoReflect() protoreflect.Message {
-	mi := &file_cart_actor_proto_msgTypes[2]
-	if x != nil {
-		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
-		if ms.LoadMessageInfo() == nil {
-			ms.StoreMessageInfo(mi)
-		}
-		return ms
-	}
-	return mi.MessageOf(x)
-}
-
-// Deprecated: Use StateRequest.ProtoReflect.Descriptor instead.
-func (*StateRequest) Descriptor() ([]byte, []int) {
-	return file_cart_actor_proto_rawDescGZIP(), []int{2}
-}
-
-func (x *StateRequest) GetCartId() string {
-	if x != nil {
-		return x.CartId
-	}
-	return ""
-}
-
-// StateReply mirrors MutationReply for consistency.
-type StateReply struct {
-	state         protoimpl.MessageState `protogen:"open.v1"`
-	StatusCode    int32                  `protobuf:"varint,1,opt,name=status_code,json=statusCode,proto3" json:"status_code,omitempty"`
-	Payload       []byte                 `protobuf:"bytes,2,opt,name=payload,proto3" json:"payload,omitempty"` // JSON cart state or error string
-	unknownFields protoimpl.UnknownFields
-	sizeCache     protoimpl.SizeCache
-}
-
-func (x *StateReply) Reset() {
-	*x = StateReply{}
-	mi := &file_cart_actor_proto_msgTypes[3]
-	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
-	ms.StoreMessageInfo(mi)
-}
-
-func (x *StateReply) String() string {
-	return protoimpl.X.MessageStringOf(x)
-}
-
-func (*StateReply) ProtoMessage() {}
-
-func (x *StateReply) ProtoReflect() protoreflect.Message {
-	mi := &file_cart_actor_proto_msgTypes[3]
-	if x != nil {
-		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
-		if ms.LoadMessageInfo() == nil {
-			ms.StoreMessageInfo(mi)
-		}
-		return ms
-	}
-	return mi.MessageOf(x)
-}
-
-// Deprecated: Use StateReply.ProtoReflect.Descriptor instead.
-func (*StateReply) Descriptor() ([]byte, []int) {
-	return file_cart_actor_proto_rawDescGZIP(), []int{3}
-}
-
-func (x *StateReply) GetStatusCode() int32 {
-	if x != nil {
-		return x.StatusCode
-	}
-	return 0
-}
-
-func (x *StateReply) GetPayload() []byte {
-	if x != nil {
-		return x.Payload
-	}
-	return nil
-}
-
-var File_cart_actor_proto protoreflect.FileDescriptor
-
-const file_cart_actor_proto_rawDesc = "" +
-	"\n" +
-	"\x10cart_actor.proto\x12\bmessages\"\x9b\x01\n" +
-	"\x0fMutationRequest\x12\x17\n" +
-	"\acart_id\x18\x01 \x01(\tR\x06cartId\x12*\n" +
-	"\x04type\x18\x02 \x01(\x0e2\x16.messages.MutationTypeR\x04type\x12\x18\n" +
-	"\apayload\x18\x03 \x01(\fR\apayload\x12)\n" +
-	"\x10client_timestamp\x18\x04 \x01(\x03R\x0fclientTimestamp\"J\n" +
-	"\rMutationReply\x12\x1f\n" +
-	"\vstatus_code\x18\x01 \x01(\x05R\n" +
-	"statusCode\x12\x18\n" +
-	"\apayload\x18\x02 \x01(\fR\apayload\"'\n" +
-	"\fStateRequest\x12\x17\n" +
-	"\acart_id\x18\x01 \x01(\tR\x06cartId\"G\n" +
-	"\n" +
-	"StateReply\x12\x1f\n" +
-	"\vstatus_code\x18\x01 \x01(\x05R\n" +
-	"statusCode\x12\x18\n" +
-	"\apayload\x18\x02 \x01(\fR\apayload*\xcd\x02\n" +
-	"\fMutationType\x12\x1d\n" +
-	"\x19MUTATION_TYPE_UNSPECIFIED\x10\x00\x12\x18\n" +
-	"\x14MUTATION_ADD_REQUEST\x10\x01\x12\x15\n" +
-	"\x11MUTATION_ADD_ITEM\x10\x02\x12\x18\n" +
-	"\x14MUTATION_REMOVE_ITEM\x10\x04\x12\x1c\n" +
-	"\x18MUTATION_REMOVE_DELIVERY\x10\x05\x12\x1c\n" +
-	"\x18MUTATION_CHANGE_QUANTITY\x10\x06\x12\x19\n" +
-	"\x15MUTATION_SET_DELIVERY\x10\a\x12\x1d\n" +
-	"\x19MUTATION_SET_PICKUP_POINT\x10\b\x12\"\n" +
-	"\x1eMUTATION_CREATE_CHECKOUT_ORDER\x10\t\x12\x1b\n" +
-	"\x17MUTATION_SET_CART_ITEMS\x10\n" +
-	"\x12\x1c\n" +
-	"\x18MUTATION_ORDER_COMPLETED\x10\v2\x83\x01\n" +
-	"\tCartActor\x12<\n" +
-	"\x06Mutate\x12\x19.messages.MutationRequest\x1a\x17.messages.MutationReply\x128\n" +
-	"\bGetState\x12\x16.messages.StateRequest\x1a\x14.messages.StateReplyB\fZ\n" +
-	".;messagesb\x06proto3"
-
-var (
-	file_cart_actor_proto_rawDescOnce sync.Once
-	file_cart_actor_proto_rawDescData []byte
-)
-
-func file_cart_actor_proto_rawDescGZIP() []byte {
-	file_cart_actor_proto_rawDescOnce.Do(func() {
-		file_cart_actor_proto_rawDescData = protoimpl.X.CompressGZIP(unsafe.Slice(unsafe.StringData(file_cart_actor_proto_rawDesc), len(file_cart_actor_proto_rawDesc)))
-	})
-	return file_cart_actor_proto_rawDescData
-}
-
-var file_cart_actor_proto_enumTypes = make([]protoimpl.EnumInfo, 1)
-var file_cart_actor_proto_msgTypes = make([]protoimpl.MessageInfo, 4)
-var file_cart_actor_proto_goTypes = []any{
-	(MutationType)(0),       // 0: messages.MutationType
-	(*MutationRequest)(nil), // 1: messages.MutationRequest
-	(*MutationReply)(nil),   // 2: messages.MutationReply
-	(*StateRequest)(nil),    // 3: messages.StateRequest
-	(*StateReply)(nil),      // 4: messages.StateReply
-}
-var file_cart_actor_proto_depIdxs = []int32{
-	0, // 0: messages.MutationRequest.type:type_name -> messages.MutationType
-	1, // 1: messages.CartActor.Mutate:input_type -> messages.MutationRequest
-	3, // 2: messages.CartActor.GetState:input_type -> messages.StateRequest
-	2, // 3: messages.CartActor.Mutate:output_type -> messages.MutationReply
-	4, // 4: messages.CartActor.GetState:output_type -> messages.StateReply
-	3, // [3:5] is the sub-list for method output_type
-	1, // [1:3] is the sub-list for method input_type
-	1, // [1:1] is the sub-list for extension type_name
-	1, // [1:1] is the sub-list for extension extendee
-	0, // [0:1] is the sub-list for field type_name
-}
-
-func init() { file_cart_actor_proto_init() }
-func file_cart_actor_proto_init() {
-	if File_cart_actor_proto != nil {
-		return
-	}
-	type x struct{}
-	out := protoimpl.TypeBuilder{
-		File: protoimpl.DescBuilder{
-			GoPackagePath: reflect.TypeOf(x{}).PkgPath(),
-			RawDescriptor: unsafe.Slice(unsafe.StringData(file_cart_actor_proto_rawDesc), len(file_cart_actor_proto_rawDesc)),
-			NumEnums:      1,
-			NumMessages:   4,
-			NumExtensions: 0,
-			NumServices:   1,
-		},
-		GoTypes:           file_cart_actor_proto_goTypes,
-		DependencyIndexes: file_cart_actor_proto_depIdxs,
-		EnumInfos:         file_cart_actor_proto_enumTypes,
-		MessageInfos:      file_cart_actor_proto_msgTypes,
-	}.Build()
-	File_cart_actor_proto = out.File
-	file_cart_actor_proto_goTypes = nil
-	file_cart_actor_proto_depIdxs = nil
-}

proto/cart_actor.proto

@@ -1,89 +0,0 @@
-syntax = "proto3";
-
-package messages;
-
-option go_package = ".;messages";
-
-// -----------------------------------------------------------------------------
-// Cart Actor gRPC API (Envelope Variant)
-// -----------------------------------------------------------------------------
-// This service replaces the legacy custom TCP frame protocol used on port 1337.
-// It keeps the existing per-mutation proto messages (defined in messages.proto)
-// serialized into an opaque `bytes payload` field for minimal refactor cost.
-// The numeric values in MutationType MUST match the legacy message type
-// constants (see message-types.go) so persisted event logs replay correctly.
-// -----------------------------------------------------------------------------
-
-// MutationType corresponds 1:1 with the legacy uint16 message type constants.
-enum MutationType {
-  MUTATION_TYPE_UNSPECIFIED        = 0;
-  MUTATION_ADD_REQUEST             = 1;
-  MUTATION_ADD_ITEM                = 2;
-  // (3 was unused / reserved in legacy framing)
-  MUTATION_REMOVE_ITEM             = 4;
-  MUTATION_REMOVE_DELIVERY         = 5;
-  MUTATION_CHANGE_QUANTITY         = 6;
-  MUTATION_SET_DELIVERY            = 7;
-  MUTATION_SET_PICKUP_POINT        = 8;
-  MUTATION_CREATE_CHECKOUT_ORDER   = 9;
-  MUTATION_SET_CART_ITEMS          = 10;
-  MUTATION_ORDER_COMPLETED         = 11;
-}
-
-// MutationRequest is an envelope:
-// - cart_id: string form of CartId (legacy 16-byte array truncated/padded).
-// - type: mutation kind (see enum).
-// - payload: serialized underlying proto message (AddRequest, AddItem, etc.).
-// - client_timestamp: optional unix timestamp; server sets if zero.
-message MutationRequest {
-  string cart_id        = 1;
-  MutationType type     = 2;
-  bytes payload         = 3;
-  int64 client_timestamp = 4;
-}
-
-// MutationReply returns a status code (legacy semantics) plus a JSON payload
-// representing the full cart state (or an error message if non-200).
-message MutationReply {
-  int32 status_code = 1;
-  bytes payload     = 2; // JSON cart state or error string
-}
-
-// StateRequest fetches current cart state without mutation.
-message StateRequest {
-  string cart_id = 1;
-}
-
-// StateReply mirrors MutationReply for consistency.
-message StateReply {
-  int32 status_code = 1;
-  bytes payload     = 2; // JSON cart state or error string
-}
-
-// CartActor exposes mutation and state retrieval for remote grains.
-service CartActor {
-  // Mutate applies a single mutation to a cart, creating the cart lazily if needed.
-  rpc Mutate(MutationRequest) returns (MutationReply);
-
-  // GetState retrieves the cart's current state (JSON).
-  rpc GetState(StateRequest) returns (StateReply);
-}
-
-// -----------------------------------------------------------------------------
-// Notes:
-//
-// 1. Generation:
-//    protoc --go_out=. --go_opt=paths=source_relative \
-//           --go-grpc_out=. --go-grpc_opt=paths=source_relative \
-//           cart_actor.proto
-//
-// 2. Underlying mutation payloads originate from messages.proto definitions.
-//    The server side will route based on MutationType and decode payload bytes
-//    using existing handler registry logic.
-//
-// 3. Future Enhancements:
-//    - Replace JSON state payload with a strongly typed CartState proto.
-//    - Add streaming RPC (e.g. WatchState) for live updates.
-//    - Migrate control plane (negotiate/ownership) into a separate proto
-//      (control_plane.proto) as per the migration plan.
-// -----------------------------------------------------------------------------

proto/cart_actor_grpc.pb.go

@@ -1,167 +0,0 @@
-// Code generated by protoc-gen-go-grpc. DO NOT EDIT.
-// versions:
-// - protoc-gen-go-grpc v1.5.1
-// - protoc             v3.21.12
-// source: cart_actor.proto
-
-package messages
-
-import (
-	context "context"
-	grpc "google.golang.org/grpc"
-	codes "google.golang.org/grpc/codes"
-	status "google.golang.org/grpc/status"
-)
-
-// This is a compile-time assertion to ensure that this generated file
-// is compatible with the grpc package it is being compiled against.
-// Requires gRPC-Go v1.64.0 or later.
-const _ = grpc.SupportPackageIsVersion9
-
-const (
-	CartActor_Mutate_FullMethodName   = "/messages.CartActor/Mutate"
-	CartActor_GetState_FullMethodName = "/messages.CartActor/GetState"
-)
-
-// CartActorClient is the client API for CartActor service.
-//
-// For semantics around ctx use and closing/ending streaming RPCs, please refer to https://pkg.go.dev/google.golang.org/grpc/?tab=doc#ClientConn.NewStream.
-//
-// CartActor exposes mutation and state retrieval for remote grains.
-type CartActorClient interface {
-	// Mutate applies a single mutation to a cart, creating the cart lazily if needed.
-	Mutate(ctx context.Context, in *MutationRequest, opts ...grpc.CallOption) (*MutationReply, error)
-	// GetState retrieves the cart's current state (JSON).
-	GetState(ctx context.Context, in *StateRequest, opts ...grpc.CallOption) (*StateReply, error)
-}
-
-type cartActorClient struct {
-	cc grpc.ClientConnInterface
-}
-
-func NewCartActorClient(cc grpc.ClientConnInterface) CartActorClient {
-	return &cartActorClient{cc}
-}
-
-func (c *cartActorClient) Mutate(ctx context.Context, in *MutationRequest, opts ...grpc.CallOption) (*MutationReply, error) {
-	cOpts := append([]grpc.CallOption{grpc.StaticMethod()}, opts...)
-	out := new(MutationReply)
-	err := c.cc.Invoke(ctx, CartActor_Mutate_FullMethodName, in, out, cOpts...)
-	if err != nil {
-		return nil, err
-	}
-	return out, nil
-}
-
-func (c *cartActorClient) GetState(ctx context.Context, in *StateRequest, opts ...grpc.CallOption) (*StateReply, error) {
-	cOpts := append([]grpc.CallOption{grpc.StaticMethod()}, opts...)
-	out := new(StateReply)
-	err := c.cc.Invoke(ctx, CartActor_GetState_FullMethodName, in, out, cOpts...)
-	if err != nil {
-		return nil, err
-	}
-	return out, nil
-}
-
-// CartActorServer is the server API for CartActor service.
-// All implementations must embed UnimplementedCartActorServer
-// for forward compatibility.
-//
-// CartActor exposes mutation and state retrieval for remote grains.
-type CartActorServer interface {
-	// Mutate applies a single mutation to a cart, creating the cart lazily if needed.
-	Mutate(context.Context, *MutationRequest) (*MutationReply, error)
-	// GetState retrieves the cart's current state (JSON).
-	GetState(context.Context, *StateRequest) (*StateReply, error)
-	mustEmbedUnimplementedCartActorServer()
-}
-
-// UnimplementedCartActorServer must be embedded to have
-// forward compatible implementations.
-//
-// NOTE: this should be embedded by value instead of pointer to avoid a nil
-// pointer dereference when methods are called.
-type UnimplementedCartActorServer struct{}
-
-func (UnimplementedCartActorServer) Mutate(context.Context, *MutationRequest) (*MutationReply, error) {
-	return nil, status.Errorf(codes.Unimplemented, "method Mutate not implemented")
-}
-func (UnimplementedCartActorServer) GetState(context.Context, *StateRequest) (*StateReply, error) {
-	return nil, status.Errorf(codes.Unimplemented, "method GetState not implemented")
-}
-func (UnimplementedCartActorServer) mustEmbedUnimplementedCartActorServer() {}
-func (UnimplementedCartActorServer) testEmbeddedByValue()                   {}
-
-// UnsafeCartActorServer may be embedded to opt out of forward compatibility for this service.
-// Use of this interface is not recommended, as added methods to CartActorServer will
-// result in compilation errors.
-type UnsafeCartActorServer interface {
-	mustEmbedUnimplementedCartActorServer()
-}
-
-func RegisterCartActorServer(s grpc.ServiceRegistrar, srv CartActorServer) {
-	// If the following call pancis, it indicates UnimplementedCartActorServer was
-	// embedded by pointer and is nil.  This will cause panics if an
-	// unimplemented method is ever invoked, so we test this at initialization
-	// time to prevent it from happening at runtime later due to I/O.
-	if t, ok := srv.(interface{ testEmbeddedByValue() }); ok {
-		t.testEmbeddedByValue()
-	}
-	s.RegisterService(&CartActor_ServiceDesc, srv)
-}
-
-func _CartActor_Mutate_Handler(srv interface{}, ctx context.Context, dec func(interface{}) error, interceptor grpc.UnaryServerInterceptor) (interface{}, error) {
-	in := new(MutationRequest)
-	if err := dec(in); err != nil {
-		return nil, err
-	}
-	if interceptor == nil {
-		return srv.(CartActorServer).Mutate(ctx, in)
-	}
-	info := &grpc.UnaryServerInfo{
-		Server:     srv,
-		FullMethod: CartActor_Mutate_FullMethodName,
-	}
-	handler := func(ctx context.Context, req interface{}) (interface{}, error) {
-		return srv.(CartActorServer).Mutate(ctx, req.(*MutationRequest))
-	}
-	return interceptor(ctx, in, info, handler)
-}
-
-func _CartActor_GetState_Handler(srv interface{}, ctx context.Context, dec func(interface{}) error, interceptor grpc.UnaryServerInterceptor) (interface{}, error) {
-	in := new(StateRequest)
-	if err := dec(in); err != nil {
-		return nil, err
-	}
-	if interceptor == nil {
-		return srv.(CartActorServer).GetState(ctx, in)
-	}
-	info := &grpc.UnaryServerInfo{
-		Server:     srv,
-		FullMethod: CartActor_GetState_FullMethodName,
-	}
-	handler := func(ctx context.Context, req interface{}) (interface{}, error) {
-		return srv.(CartActorServer).GetState(ctx, req.(*StateRequest))
-	}
-	return interceptor(ctx, in, info, handler)
-}
-
-// CartActor_ServiceDesc is the grpc.ServiceDesc for CartActor service.
-// It's only intended for direct use with grpc.RegisterService,
-// and not to be introspected or modified (even as a copy)
-var CartActor_ServiceDesc = grpc.ServiceDesc{
-	ServiceName: "messages.CartActor",
-	HandlerType: (*CartActorServer)(nil),
-	Methods: []grpc.MethodDesc{
-		{
-			MethodName: "Mutate",
-			Handler:    _CartActor_Mutate_Handler,
-		},
-		{
-			MethodName: "GetState",
-			Handler:    _CartActor_GetState_Handler,
-		},
-	},
-	Streams:  []grpc.StreamDesc{},
-	Metadata: "cart_actor.proto",
-}

proto/control_plane.pb.go

@@ -1,8 +1,8 @@
 // Code generated by protoc-gen-go. DO NOT EDIT.
 // versions:
-// 	protoc-gen-go v1.36.10
-// 	protoc        v3.21.12
-// source: control_plane.proto
+// 	protoc-gen-go v1.36.9
+// 	protoc        v6.32.1
+// source: proto/control_plane.proto
 
 package messages
 
@@ -30,7 +30,7 @@ type Empty struct {
 
 func (x *Empty) Reset() {
 	*x = Empty{}
-	mi := &file_control_plane_proto_msgTypes[0]
+	mi := &file_proto_control_plane_proto_msgTypes[0]
 	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 	ms.StoreMessageInfo(mi)
 }
@@ -42,7 +42,7 @@ func (x *Empty) String() string {
 func (*Empty) ProtoMessage() {}
 
 func (x *Empty) ProtoReflect() protoreflect.Message {
-	mi := &file_control_plane_proto_msgTypes[0]
+	mi := &file_proto_control_plane_proto_msgTypes[0]
 	if x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -55,7 +55,7 @@ func (x *Empty) ProtoReflect() protoreflect.Message {
 
 // Deprecated: Use Empty.ProtoReflect.Descriptor instead.
 func (*Empty) Descriptor() ([]byte, []int) {
-	return file_control_plane_proto_rawDescGZIP(), []int{0}
+	return file_proto_control_plane_proto_rawDescGZIP(), []int{0}
 }
 
 // Ping reply includes responding host and its current unix time (seconds).
@@ -69,7 +69,7 @@ type PingReply struct {
 
 func (x *PingReply) Reset() {
 	*x = PingReply{}
-	mi := &file_control_plane_proto_msgTypes[1]
+	mi := &file_proto_control_plane_proto_msgTypes[1]
 	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 	ms.StoreMessageInfo(mi)
 }
@@ -81,7 +81,7 @@ func (x *PingReply) String() string {
 func (*PingReply) ProtoMessage() {}
 
 func (x *PingReply) ProtoReflect() protoreflect.Message {
-	mi := &file_control_plane_proto_msgTypes[1]
+	mi := &file_proto_control_plane_proto_msgTypes[1]
 	if x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -94,7 +94,7 @@ func (x *PingReply) ProtoReflect() protoreflect.Message {
 
 // Deprecated: Use PingReply.ProtoReflect.Descriptor instead.
 func (*PingReply) Descriptor() ([]byte, []int) {
-	return file_control_plane_proto_rawDescGZIP(), []int{1}
+	return file_proto_control_plane_proto_rawDescGZIP(), []int{1}
 }
 
 func (x *PingReply) GetHost() string {
@@ -121,7 +121,7 @@ type NegotiateRequest struct {
 
 func (x *NegotiateRequest) Reset() {
 	*x = NegotiateRequest{}
-	mi := &file_control_plane_proto_msgTypes[2]
+	mi := &file_proto_control_plane_proto_msgTypes[2]
 	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 	ms.StoreMessageInfo(mi)
 }
@@ -133,7 +133,7 @@ func (x *NegotiateRequest) String() string {
 func (*NegotiateRequest) ProtoMessage() {}
 
 func (x *NegotiateRequest) ProtoReflect() protoreflect.Message {
-	mi := &file_control_plane_proto_msgTypes[2]
+	mi := &file_proto_control_plane_proto_msgTypes[2]
 	if x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -146,7 +146,7 @@ func (x *NegotiateRequest) ProtoReflect() protoreflect.Message {
 
 // Deprecated: Use NegotiateRequest.ProtoReflect.Descriptor instead.
 func (*NegotiateRequest) Descriptor() ([]byte, []int) {
-	return file_control_plane_proto_rawDescGZIP(), []int{2}
+	return file_proto_control_plane_proto_rawDescGZIP(), []int{2}
 }
 
 func (x *NegotiateRequest) GetKnownHosts() []string {
@@ -166,7 +166,7 @@ type NegotiateReply struct {
 
 func (x *NegotiateReply) Reset() {
 	*x = NegotiateReply{}
-	mi := &file_control_plane_proto_msgTypes[3]
+	mi := &file_proto_control_plane_proto_msgTypes[3]
 	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 	ms.StoreMessageInfo(mi)
 }
@@ -178,7 +178,7 @@ func (x *NegotiateReply) String() string {
 func (*NegotiateReply) ProtoMessage() {}
 
 func (x *NegotiateReply) ProtoReflect() protoreflect.Message {
-	mi := &file_control_plane_proto_msgTypes[3]
+	mi := &file_proto_control_plane_proto_msgTypes[3]
 	if x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -191,7 +191,7 @@ func (x *NegotiateReply) ProtoReflect() protoreflect.Message {
 
 // Deprecated: Use NegotiateReply.ProtoReflect.Descriptor instead.
 func (*NegotiateReply) Descriptor() ([]byte, []int) {
-	return file_control_plane_proto_rawDescGZIP(), []int{3}
+	return file_proto_control_plane_proto_rawDescGZIP(), []int{3}
 }
 
 func (x *NegotiateReply) GetHosts() []string {
@@ -204,14 +204,14 @@ func (x *NegotiateReply) GetHosts() []string {
 // CartIdsReply returns the list of cart IDs (string form) currently owned locally.
 type CartIdsReply struct {
 	state         protoimpl.MessageState `protogen:"open.v1"`
-	CartIds       []string               `protobuf:"bytes,1,rep,name=cart_ids,json=cartIds,proto3" json:"cart_ids,omitempty"`
+	CartIds       []uint64               `protobuf:"varint,1,rep,packed,name=cart_ids,json=cartIds,proto3" json:"cart_ids,omitempty"`
 	unknownFields protoimpl.UnknownFields
 	sizeCache     protoimpl.SizeCache
 }
 
 func (x *CartIdsReply) Reset() {
 	*x = CartIdsReply{}
-	mi := &file_control_plane_proto_msgTypes[4]
+	mi := &file_proto_control_plane_proto_msgTypes[4]
 	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 	ms.StoreMessageInfo(mi)
 }
@@ -223,7 +223,7 @@ func (x *CartIdsReply) String() string {
 func (*CartIdsReply) ProtoMessage() {}
 
 func (x *CartIdsReply) ProtoReflect() protoreflect.Message {
-	mi := &file_control_plane_proto_msgTypes[4]
+	mi := &file_proto_control_plane_proto_msgTypes[4]
 	if x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -236,70 +236,17 @@ func (x *CartIdsReply) ProtoReflect() protoreflect.Message {
 
 // Deprecated: Use CartIdsReply.ProtoReflect.Descriptor instead.
 func (*CartIdsReply) Descriptor() ([]byte, []int) {
-	return file_control_plane_proto_rawDescGZIP(), []int{4}
+	return file_proto_control_plane_proto_rawDescGZIP(), []int{4}
 }
 
-func (x *CartIdsReply) GetCartIds() []string {
+func (x *CartIdsReply) GetCartIds() []uint64 {
 	if x != nil {
 		return x.CartIds
 	}
 	return nil
 }
 
-// OwnerChangeRequest notifies peers that ownership of a cart moved (or is moving) to new_host.
-type OwnerChangeRequest struct {
-	state         protoimpl.MessageState `protogen:"open.v1"`
-	CartId        string                 `protobuf:"bytes,1,opt,name=cart_id,json=cartId,proto3" json:"cart_id,omitempty"`
-	NewHost       string                 `protobuf:"bytes,2,opt,name=new_host,json=newHost,proto3" json:"new_host,omitempty"`
-	unknownFields protoimpl.UnknownFields
-	sizeCache     protoimpl.SizeCache
-}
-
-func (x *OwnerChangeRequest) Reset() {
-	*x = OwnerChangeRequest{}
-	mi := &file_control_plane_proto_msgTypes[5]
-	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
-	ms.StoreMessageInfo(mi)
-}
-
-func (x *OwnerChangeRequest) String() string {
-	return protoimpl.X.MessageStringOf(x)
-}
-
-func (*OwnerChangeRequest) ProtoMessage() {}
-
-func (x *OwnerChangeRequest) ProtoReflect() protoreflect.Message {
-	mi := &file_control_plane_proto_msgTypes[5]
-	if x != nil {
-		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
-		if ms.LoadMessageInfo() == nil {
-			ms.StoreMessageInfo(mi)
-		}
-		return ms
-	}
-	return mi.MessageOf(x)
-}
-
-// Deprecated: Use OwnerChangeRequest.ProtoReflect.Descriptor instead.
-func (*OwnerChangeRequest) Descriptor() ([]byte, []int) {
-	return file_control_plane_proto_rawDescGZIP(), []int{5}
-}
-
-func (x *OwnerChangeRequest) GetCartId() string {
-	if x != nil {
-		return x.CartId
-	}
-	return ""
-}
-
-func (x *OwnerChangeRequest) GetNewHost() string {
-	if x != nil {
-		return x.NewHost
-	}
-	return ""
-}
-
-// OwnerChangeAck indicates acceptance or rejection of an ownership change.
+// OwnerChangeAck retained as response type for Closing RPC (ConfirmOwner removed).
 type OwnerChangeAck struct {
 	state         protoimpl.MessageState `protogen:"open.v1"`
 	Accepted      bool                   `protobuf:"varint,1,opt,name=accepted,proto3" json:"accepted,omitempty"`
@@ -310,7 +257,7 @@ type OwnerChangeAck struct {
 
 func (x *OwnerChangeAck) Reset() {
 	*x = OwnerChangeAck{}
-	mi := &file_control_plane_proto_msgTypes[6]
+	mi := &file_proto_control_plane_proto_msgTypes[5]
 	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 	ms.StoreMessageInfo(mi)
 }
@@ -322,7 +269,7 @@ func (x *OwnerChangeAck) String() string {
 func (*OwnerChangeAck) ProtoMessage() {}
 
 func (x *OwnerChangeAck) ProtoReflect() protoreflect.Message {
-	mi := &file_control_plane_proto_msgTypes[6]
+	mi := &file_proto_control_plane_proto_msgTypes[5]
 	if x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -335,7 +282,7 @@ func (x *OwnerChangeAck) ProtoReflect() protoreflect.Message {
 
 // Deprecated: Use OwnerChangeAck.ProtoReflect.Descriptor instead.
 func (*OwnerChangeAck) Descriptor() ([]byte, []int) {
-	return file_control_plane_proto_rawDescGZIP(), []int{6}
+	return file_proto_control_plane_proto_rawDescGZIP(), []int{5}
 }
 
 func (x *OwnerChangeAck) GetAccepted() bool {
@@ -362,7 +309,7 @@ type ClosingNotice struct {
 
 func (x *ClosingNotice) Reset() {
 	*x = ClosingNotice{}
-	mi := &file_control_plane_proto_msgTypes[7]
+	mi := &file_proto_control_plane_proto_msgTypes[6]
 	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 	ms.StoreMessageInfo(mi)
 }
@@ -374,7 +321,7 @@ func (x *ClosingNotice) String() string {
 func (*ClosingNotice) ProtoMessage() {}
 
 func (x *ClosingNotice) ProtoReflect() protoreflect.Message {
-	mi := &file_control_plane_proto_msgTypes[7]
+	mi := &file_proto_control_plane_proto_msgTypes[6]
 	if x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -387,7 +334,7 @@ func (x *ClosingNotice) ProtoReflect() protoreflect.Message {
 
 // Deprecated: Use ClosingNotice.ProtoReflect.Descriptor instead.
 func (*ClosingNotice) Descriptor() ([]byte, []int) {
-	return file_control_plane_proto_rawDescGZIP(), []int{7}
+	return file_proto_control_plane_proto_rawDescGZIP(), []int{6}
 }
 
 func (x *ClosingNotice) GetHost() string {
@@ -397,11 +344,118 @@ func (x *ClosingNotice) GetHost() string {
 	return ""
 }
 
-var File_control_plane_proto protoreflect.FileDescriptor
+// OwnershipAnnounce broadcasts first-touch ownership claims for cart IDs.
+// First claim wins; receivers SHOULD NOT overwrite an existing different owner.
+type OwnershipAnnounce struct {
+	state         protoimpl.MessageState `protogen:"open.v1"`
+	Host          string                 `protobuf:"bytes,1,opt,name=host,proto3" json:"host,omitempty"`                              // announcing host
+	CartIds       []uint64               `protobuf:"varint,2,rep,packed,name=cart_ids,json=cartIds,proto3" json:"cart_ids,omitempty"` // newly claimed cart ids
+	unknownFields protoimpl.UnknownFields
+	sizeCache     protoimpl.SizeCache
+}
 
-const file_control_plane_proto_rawDesc = "" +
+func (x *OwnershipAnnounce) Reset() {
+	*x = OwnershipAnnounce{}
+	mi := &file_proto_control_plane_proto_msgTypes[7]
+	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+	ms.StoreMessageInfo(mi)
+}
+
+func (x *OwnershipAnnounce) String() string {
+	return protoimpl.X.MessageStringOf(x)
+}
+
+func (*OwnershipAnnounce) ProtoMessage() {}
+
+func (x *OwnershipAnnounce) ProtoReflect() protoreflect.Message {
+	mi := &file_proto_control_plane_proto_msgTypes[7]
+	if x != nil {
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		if ms.LoadMessageInfo() == nil {
+			ms.StoreMessageInfo(mi)
+		}
+		return ms
+	}
+	return mi.MessageOf(x)
+}
+
+// Deprecated: Use OwnershipAnnounce.ProtoReflect.Descriptor instead.
+func (*OwnershipAnnounce) Descriptor() ([]byte, []int) {
+	return file_proto_control_plane_proto_rawDescGZIP(), []int{7}
+}
+
+func (x *OwnershipAnnounce) GetHost() string {
+	if x != nil {
+		return x.Host
+	}
+	return ""
+}
+
+func (x *OwnershipAnnounce) GetCartIds() []uint64 {
+	if x != nil {
+		return x.CartIds
+	}
+	return nil
+}
+
+// ExpiryAnnounce broadcasts that a host evicted the provided cart IDs.
+type ExpiryAnnounce struct {
+	state         protoimpl.MessageState `protogen:"open.v1"`
+	Host          string                 `protobuf:"bytes,1,opt,name=host,proto3" json:"host,omitempty"`
+	CartIds       []uint64               `protobuf:"varint,2,rep,packed,name=cart_ids,json=cartIds,proto3" json:"cart_ids,omitempty"`
+	unknownFields protoimpl.UnknownFields
+	sizeCache     protoimpl.SizeCache
+}
+
+func (x *ExpiryAnnounce) Reset() {
+	*x = ExpiryAnnounce{}
+	mi := &file_proto_control_plane_proto_msgTypes[8]
+	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+	ms.StoreMessageInfo(mi)
+}
+
+func (x *ExpiryAnnounce) String() string {
+	return protoimpl.X.MessageStringOf(x)
+}
+
+func (*ExpiryAnnounce) ProtoMessage() {}
+
+func (x *ExpiryAnnounce) ProtoReflect() protoreflect.Message {
+	mi := &file_proto_control_plane_proto_msgTypes[8]
+	if x != nil {
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		if ms.LoadMessageInfo() == nil {
+			ms.StoreMessageInfo(mi)
+		}
+		return ms
+	}
+	return mi.MessageOf(x)
+}
+
+// Deprecated: Use ExpiryAnnounce.ProtoReflect.Descriptor instead.
+func (*ExpiryAnnounce) Descriptor() ([]byte, []int) {
+	return file_proto_control_plane_proto_rawDescGZIP(), []int{8}
+}
+
+func (x *ExpiryAnnounce) GetHost() string {
+	if x != nil {
+		return x.Host
+	}
+	return ""
+}
+
+func (x *ExpiryAnnounce) GetCartIds() []uint64 {
+	if x != nil {
+		return x.CartIds
+	}
+	return nil
+}
+
+var File_proto_control_plane_proto protoreflect.FileDescriptor
+
+const file_proto_control_plane_proto_rawDesc = "" +
 	"\n" +
-	"\x13control_plane.proto\x12\bmessages\"\a\n" +
+	"\x19proto/control_plane.proto\x12\bmessages\"\a\n" +
 	"\x05Empty\"<\n" +
 	"\tPingReply\x12\x12\n" +
 	"\x04host\x18\x01 \x01(\tR\x04host\x12\x1b\n" +
@@ -412,85 +466,91 @@ const file_control_plane_proto_rawDesc = "" +
 	"\x0eNegotiateReply\x12\x14\n" +
 	"\x05hosts\x18\x01 \x03(\tR\x05hosts\")\n" +
 	"\fCartIdsReply\x12\x19\n" +
-	"\bcart_ids\x18\x01 \x03(\tR\acartIds\"H\n" +
-	"\x12OwnerChangeRequest\x12\x17\n" +
-	"\acart_id\x18\x01 \x01(\tR\x06cartId\x12\x19\n" +
-	"\bnew_host\x18\x02 \x01(\tR\anewHost\"F\n" +
+	"\bcart_ids\x18\x01 \x03(\x04R\acartIds\"F\n" +
 	"\x0eOwnerChangeAck\x12\x1a\n" +
 	"\baccepted\x18\x01 \x01(\bR\baccepted\x12\x18\n" +
 	"\amessage\x18\x02 \x01(\tR\amessage\"#\n" +
 	"\rClosingNotice\x12\x12\n" +
-	"\x04host\x18\x01 \x01(\tR\x04host2\xbc\x02\n" +
+	"\x04host\x18\x01 \x01(\tR\x04host\"B\n" +
+	"\x11OwnershipAnnounce\x12\x12\n" +
+	"\x04host\x18\x01 \x01(\tR\x04host\x12\x19\n" +
+	"\bcart_ids\x18\x02 \x03(\x04R\acartIds\"?\n" +
+	"\x0eExpiryAnnounce\x12\x12\n" +
+	"\x04host\x18\x01 \x01(\tR\x04host\x12\x19\n" +
+	"\bcart_ids\x18\x02 \x03(\x04R\acartIds2\x86\x03\n" +
 	"\fControlPlane\x12,\n" +
 	"\x04Ping\x12\x0f.messages.Empty\x1a\x13.messages.PingReply\x12A\n" +
 	"\tNegotiate\x12\x1a.messages.NegotiateRequest\x1a\x18.messages.NegotiateReply\x125\n" +
 	"\n" +
-	"GetCartIds\x12\x0f.messages.Empty\x1a\x16.messages.CartIdsReply\x12F\n" +
-	"\fConfirmOwner\x12\x1c.messages.OwnerChangeRequest\x1a\x18.messages.OwnerChangeAck\x12<\n" +
-	"\aClosing\x12\x17.messages.ClosingNotice\x1a\x18.messages.OwnerChangeAckB\fZ\n" +
-	".;messagesb\x06proto3"
+	"GetCartIds\x12\x0f.messages.Empty\x1a\x16.messages.CartIdsReply\x12J\n" +
+	"\x11AnnounceOwnership\x12\x1b.messages.OwnershipAnnounce\x1a\x18.messages.OwnerChangeAck\x12D\n" +
+	"\x0eAnnounceExpiry\x12\x18.messages.ExpiryAnnounce\x1a\x18.messages.OwnerChangeAck\x12<\n" +
+	"\aClosing\x12\x17.messages.ClosingNotice\x1a\x18.messages.OwnerChangeAckB.Z,git.tornberg.me/go-cart-actor/proto;messagesb\x06proto3"
 
 var (
-	file_control_plane_proto_rawDescOnce sync.Once
-	file_control_plane_proto_rawDescData []byte
+	file_proto_control_plane_proto_rawDescOnce sync.Once
+	file_proto_control_plane_proto_rawDescData []byte
 )
 
-func file_control_plane_proto_rawDescGZIP() []byte {
-	file_control_plane_proto_rawDescOnce.Do(func() {
-		file_control_plane_proto_rawDescData = protoimpl.X.CompressGZIP(unsafe.Slice(unsafe.StringData(file_control_plane_proto_rawDesc), len(file_control_plane_proto_rawDesc)))
+func file_proto_control_plane_proto_rawDescGZIP() []byte {
+	file_proto_control_plane_proto_rawDescOnce.Do(func() {
+		file_proto_control_plane_proto_rawDescData = protoimpl.X.CompressGZIP(unsafe.Slice(unsafe.StringData(file_proto_control_plane_proto_rawDesc), len(file_proto_control_plane_proto_rawDesc)))
 	})
-	return file_control_plane_proto_rawDescData
+	return file_proto_control_plane_proto_rawDescData
 }
 
-var file_control_plane_proto_msgTypes = make([]protoimpl.MessageInfo, 8)
-var file_control_plane_proto_goTypes = []any{
-	(*Empty)(nil),              // 0: messages.Empty
-	(*PingReply)(nil),          // 1: messages.PingReply
-	(*NegotiateRequest)(nil),   // 2: messages.NegotiateRequest
-	(*NegotiateReply)(nil),     // 3: messages.NegotiateReply
-	(*CartIdsReply)(nil),       // 4: messages.CartIdsReply
-	(*OwnerChangeRequest)(nil), // 5: messages.OwnerChangeRequest
-	(*OwnerChangeAck)(nil),     // 6: messages.OwnerChangeAck
-	(*ClosingNotice)(nil),      // 7: messages.ClosingNotice
+var file_proto_control_plane_proto_msgTypes = make([]protoimpl.MessageInfo, 9)
+var file_proto_control_plane_proto_goTypes = []any{
+	(*Empty)(nil),             // 0: messages.Empty
+	(*PingReply)(nil),         // 1: messages.PingReply
+	(*NegotiateRequest)(nil),  // 2: messages.NegotiateRequest
+	(*NegotiateReply)(nil),    // 3: messages.NegotiateReply
+	(*CartIdsReply)(nil),      // 4: messages.CartIdsReply
+	(*OwnerChangeAck)(nil),    // 5: messages.OwnerChangeAck
+	(*ClosingNotice)(nil),     // 6: messages.ClosingNotice
+	(*OwnershipAnnounce)(nil), // 7: messages.OwnershipAnnounce
+	(*ExpiryAnnounce)(nil),    // 8: messages.ExpiryAnnounce
 }
-var file_control_plane_proto_depIdxs = []int32{
+var file_proto_control_plane_proto_depIdxs = []int32{
 	0, // 0: messages.ControlPlane.Ping:input_type -> messages.Empty
 	2, // 1: messages.ControlPlane.Negotiate:input_type -> messages.NegotiateRequest
 	0, // 2: messages.ControlPlane.GetCartIds:input_type -> messages.Empty
-	5, // 3: messages.ControlPlane.ConfirmOwner:input_type -> messages.OwnerChangeRequest
-	7, // 4: messages.ControlPlane.Closing:input_type -> messages.ClosingNotice
-	1, // 5: messages.ControlPlane.Ping:output_type -> messages.PingReply
-	3, // 6: messages.ControlPlane.Negotiate:output_type -> messages.NegotiateReply
-	4, // 7: messages.ControlPlane.GetCartIds:output_type -> messages.CartIdsReply
-	6, // 8: messages.ControlPlane.ConfirmOwner:output_type -> messages.OwnerChangeAck
-	6, // 9: messages.ControlPlane.Closing:output_type -> messages.OwnerChangeAck
-	5, // [5:10] is the sub-list for method output_type
-	0, // [0:5] is the sub-list for method input_type
+	7, // 3: messages.ControlPlane.AnnounceOwnership:input_type -> messages.OwnershipAnnounce
+	8, // 4: messages.ControlPlane.AnnounceExpiry:input_type -> messages.ExpiryAnnounce
+	6, // 5: messages.ControlPlane.Closing:input_type -> messages.ClosingNotice
+	1, // 6: messages.ControlPlane.Ping:output_type -> messages.PingReply
+	3, // 7: messages.ControlPlane.Negotiate:output_type -> messages.NegotiateReply
+	4, // 8: messages.ControlPlane.GetCartIds:output_type -> messages.CartIdsReply
+	5, // 9: messages.ControlPlane.AnnounceOwnership:output_type -> messages.OwnerChangeAck
+	5, // 10: messages.ControlPlane.AnnounceExpiry:output_type -> messages.OwnerChangeAck
+	5, // 11: messages.ControlPlane.Closing:output_type -> messages.OwnerChangeAck
+	6, // [6:12] is the sub-list for method output_type
+	0, // [0:6] is the sub-list for method input_type
 	0, // [0:0] is the sub-list for extension type_name
 	0, // [0:0] is the sub-list for extension extendee
 	0, // [0:0] is the sub-list for field type_name
 }
 
-func init() { file_control_plane_proto_init() }
-func file_control_plane_proto_init() {
-	if File_control_plane_proto != nil {
+func init() { file_proto_control_plane_proto_init() }
+func file_proto_control_plane_proto_init() {
+	if File_proto_control_plane_proto != nil {
 		return
 	}
 	type x struct{}
 	out := protoimpl.TypeBuilder{
 		File: protoimpl.DescBuilder{
 			GoPackagePath: reflect.TypeOf(x{}).PkgPath(),
-			RawDescriptor: unsafe.Slice(unsafe.StringData(file_control_plane_proto_rawDesc), len(file_control_plane_proto_rawDesc)),
+			RawDescriptor: unsafe.Slice(unsafe.StringData(file_proto_control_plane_proto_rawDesc), len(file_proto_control_plane_proto_rawDesc)),
 			NumEnums:      0,
-			NumMessages:   8,
+			NumMessages:   9,
 			NumExtensions: 0,
 			NumServices:   1,
 		},
-		GoTypes:           file_control_plane_proto_goTypes,
-		DependencyIndexes: file_control_plane_proto_depIdxs,
-		MessageInfos:      file_control_plane_proto_msgTypes,
+		GoTypes:           file_proto_control_plane_proto_goTypes,
+		DependencyIndexes: file_proto_control_plane_proto_depIdxs,
+		MessageInfos:      file_proto_control_plane_proto_msgTypes,
 	}.Build()
-	File_control_plane_proto = out.File
-	file_control_plane_proto_goTypes = nil
-	file_control_plane_proto_depIdxs = nil
+	File_proto_control_plane_proto = out.File
+	file_proto_control_plane_proto_goTypes = nil
+	file_proto_control_plane_proto_depIdxs = nil
 }

proto/control_plane.proto

@@ -2,7 +2,7 @@ syntax = "proto3";
 
 package messages;
 
-option go_package = ".;messages";
+option go_package = "git.tornberg.me/go-cart-actor/proto;messages";
 
 // -----------------------------------------------------------------------------
 // Control Plane gRPC API
@@ -11,7 +11,7 @@ option go_package = ".;messages";
 // Responsibilities:
 //   - Liveness (Ping)
 //   - Membership negotiation (Negotiate)
-//   - Cart ownership change propagation (ConfirmOwner)
+//   - Deterministic ring-based ownership (ConfirmOwner RPC removed)
 //   - Cart ID listing for remote grain spawning (GetCartIds)
 //   - Graceful shutdown notifications (Closing)
 // No authentication / TLS is defined initially (can be added later).
@@ -38,16 +38,10 @@ message NegotiateReply {
 
 // CartIdsReply returns the list of cart IDs (string form) currently owned locally.
 message CartIdsReply {
-  repeated string cart_ids = 1;
+  repeated uint64 cart_ids = 1;
 }
 
-// OwnerChangeRequest notifies peers that ownership of a cart moved (or is moving) to new_host.
-message OwnerChangeRequest {
-  string cart_id = 1;
-  string new_host = 2;
-}
-
-// OwnerChangeAck indicates acceptance or rejection of an ownership change.
+// OwnerChangeAck retained as response type for Closing RPC (ConfirmOwner removed).
 message OwnerChangeAck {
   bool accepted = 1;
   string message = 2;
@@ -58,6 +52,19 @@ message ClosingNotice {
   string host = 1;
 }
 
+// OwnershipAnnounce broadcasts first-touch ownership claims for cart IDs.
+// First claim wins; receivers SHOULD NOT overwrite an existing different owner.
+message OwnershipAnnounce {
+  string host = 1;               // announcing host
+  repeated uint64 cart_ids = 2;   // newly claimed cart ids
+}
+
+// ExpiryAnnounce broadcasts that a host evicted the provided cart IDs.
+message ExpiryAnnounce {
+  string host = 1;
+  repeated uint64 cart_ids = 2;
+}
+
 // ControlPlane defines cluster coordination and ownership operations.
 service ControlPlane {
   // Ping for liveness; lightweight health signal.
@@ -69,8 +76,13 @@ service ControlPlane {
   // GetCartIds lists currently owned cart IDs on this node.
   rpc GetCartIds(Empty) returns (CartIdsReply);
 
-  // ConfirmOwner announces/asks peers to acknowledge ownership transfer.
-  rpc ConfirmOwner(OwnerChangeRequest) returns (OwnerChangeAck);
+  // ConfirmOwner RPC removed (was legacy ownership acknowledgement; ring-based ownership now authoritative)
+
+  // Ownership announcement: first-touch claim broadcast (idempotent; best-effort).
+  rpc AnnounceOwnership(OwnershipAnnounce) returns (OwnerChangeAck);
+
+  // Expiry announcement: drop remote ownership hints when local TTL expires.
+  rpc AnnounceExpiry(ExpiryAnnounce) returns (OwnerChangeAck);
 
   // Closing announces graceful shutdown so peers can proactively adjust.
   rpc Closing(ClosingNotice) returns (OwnerChangeAck);

proto/control_plane_grpc.pb.go

@@ -1,8 +1,8 @@
 // Code generated by protoc-gen-go-grpc. DO NOT EDIT.
 // versions:
 // - protoc-gen-go-grpc v1.5.1
-// - protoc             v3.21.12
-// source: control_plane.proto
+// - protoc             v6.32.1
+// source: proto/control_plane.proto
 
 package messages
 
@@ -19,11 +19,12 @@ import (
 const _ = grpc.SupportPackageIsVersion9
 
 const (
-	ControlPlane_Ping_FullMethodName         = "/messages.ControlPlane/Ping"
-	ControlPlane_Negotiate_FullMethodName    = "/messages.ControlPlane/Negotiate"
-	ControlPlane_GetCartIds_FullMethodName   = "/messages.ControlPlane/GetCartIds"
-	ControlPlane_ConfirmOwner_FullMethodName = "/messages.ControlPlane/ConfirmOwner"
-	ControlPlane_Closing_FullMethodName      = "/messages.ControlPlane/Closing"
+	ControlPlane_Ping_FullMethodName              = "/messages.ControlPlane/Ping"
+	ControlPlane_Negotiate_FullMethodName         = "/messages.ControlPlane/Negotiate"
+	ControlPlane_GetCartIds_FullMethodName        = "/messages.ControlPlane/GetCartIds"
+	ControlPlane_AnnounceOwnership_FullMethodName = "/messages.ControlPlane/AnnounceOwnership"
+	ControlPlane_AnnounceExpiry_FullMethodName    = "/messages.ControlPlane/AnnounceExpiry"
+	ControlPlane_Closing_FullMethodName           = "/messages.ControlPlane/Closing"
 )
 
 // ControlPlaneClient is the client API for ControlPlane service.
@@ -38,8 +39,10 @@ type ControlPlaneClient interface {
 	Negotiate(ctx context.Context, in *NegotiateRequest, opts ...grpc.CallOption) (*NegotiateReply, error)
 	// GetCartIds lists currently owned cart IDs on this node.
 	GetCartIds(ctx context.Context, in *Empty, opts ...grpc.CallOption) (*CartIdsReply, error)
-	// ConfirmOwner announces/asks peers to acknowledge ownership transfer.
-	ConfirmOwner(ctx context.Context, in *OwnerChangeRequest, opts ...grpc.CallOption) (*OwnerChangeAck, error)
+	// Ownership announcement: first-touch claim broadcast (idempotent; best-effort).
+	AnnounceOwnership(ctx context.Context, in *OwnershipAnnounce, opts ...grpc.CallOption) (*OwnerChangeAck, error)
+	// Expiry announcement: drop remote ownership hints when local TTL expires.
+	AnnounceExpiry(ctx context.Context, in *ExpiryAnnounce, opts ...grpc.CallOption) (*OwnerChangeAck, error)
 	// Closing announces graceful shutdown so peers can proactively adjust.
 	Closing(ctx context.Context, in *ClosingNotice, opts ...grpc.CallOption) (*OwnerChangeAck, error)
 }
@@ -82,10 +85,20 @@ func (c *controlPlaneClient) GetCartIds(ctx context.Context, in *Empty, opts ...
 	return out, nil
 }
 
-func (c *controlPlaneClient) ConfirmOwner(ctx context.Context, in *OwnerChangeRequest, opts ...grpc.CallOption) (*OwnerChangeAck, error) {
+func (c *controlPlaneClient) AnnounceOwnership(ctx context.Context, in *OwnershipAnnounce, opts ...grpc.CallOption) (*OwnerChangeAck, error) {
 	cOpts := append([]grpc.CallOption{grpc.StaticMethod()}, opts...)
 	out := new(OwnerChangeAck)
-	err := c.cc.Invoke(ctx, ControlPlane_ConfirmOwner_FullMethodName, in, out, cOpts...)
+	err := c.cc.Invoke(ctx, ControlPlane_AnnounceOwnership_FullMethodName, in, out, cOpts...)
+	if err != nil {
+		return nil, err
+	}
+	return out, nil
+}
+
+func (c *controlPlaneClient) AnnounceExpiry(ctx context.Context, in *ExpiryAnnounce, opts ...grpc.CallOption) (*OwnerChangeAck, error) {
+	cOpts := append([]grpc.CallOption{grpc.StaticMethod()}, opts...)
+	out := new(OwnerChangeAck)
+	err := c.cc.Invoke(ctx, ControlPlane_AnnounceExpiry_FullMethodName, in, out, cOpts...)
 	if err != nil {
 		return nil, err
 	}
@@ -114,8 +127,10 @@ type ControlPlaneServer interface {
 	Negotiate(context.Context, *NegotiateRequest) (*NegotiateReply, error)
 	// GetCartIds lists currently owned cart IDs on this node.
 	GetCartIds(context.Context, *Empty) (*CartIdsReply, error)
-	// ConfirmOwner announces/asks peers to acknowledge ownership transfer.
-	ConfirmOwner(context.Context, *OwnerChangeRequest) (*OwnerChangeAck, error)
+	// Ownership announcement: first-touch claim broadcast (idempotent; best-effort).
+	AnnounceOwnership(context.Context, *OwnershipAnnounce) (*OwnerChangeAck, error)
+	// Expiry announcement: drop remote ownership hints when local TTL expires.
+	AnnounceExpiry(context.Context, *ExpiryAnnounce) (*OwnerChangeAck, error)
 	// Closing announces graceful shutdown so peers can proactively adjust.
 	Closing(context.Context, *ClosingNotice) (*OwnerChangeAck, error)
 	mustEmbedUnimplementedControlPlaneServer()
@@ -137,8 +152,11 @@ func (UnimplementedControlPlaneServer) Negotiate(context.Context, *NegotiateRequ
 func (UnimplementedControlPlaneServer) GetCartIds(context.Context, *Empty) (*CartIdsReply, error) {
 	return nil, status.Errorf(codes.Unimplemented, "method GetCartIds not implemented")
 }
-func (UnimplementedControlPlaneServer) ConfirmOwner(context.Context, *OwnerChangeRequest) (*OwnerChangeAck, error) {
-	return nil, status.Errorf(codes.Unimplemented, "method ConfirmOwner not implemented")
+func (UnimplementedControlPlaneServer) AnnounceOwnership(context.Context, *OwnershipAnnounce) (*OwnerChangeAck, error) {
+	return nil, status.Errorf(codes.Unimplemented, "method AnnounceOwnership not implemented")
+}
+func (UnimplementedControlPlaneServer) AnnounceExpiry(context.Context, *ExpiryAnnounce) (*OwnerChangeAck, error) {
+	return nil, status.Errorf(codes.Unimplemented, "method AnnounceExpiry not implemented")
 }
 func (UnimplementedControlPlaneServer) Closing(context.Context, *ClosingNotice) (*OwnerChangeAck, error) {
 	return nil, status.Errorf(codes.Unimplemented, "method Closing not implemented")
@@ -218,20 +236,38 @@ func _ControlPlane_GetCartIds_Handler(srv interface{}, ctx context.Context, dec
 	return interceptor(ctx, in, info, handler)
 }
 
-func _ControlPlane_ConfirmOwner_Handler(srv interface{}, ctx context.Context, dec func(interface{}) error, interceptor grpc.UnaryServerInterceptor) (interface{}, error) {
-	in := new(OwnerChangeRequest)
+func _ControlPlane_AnnounceOwnership_Handler(srv interface{}, ctx context.Context, dec func(interface{}) error, interceptor grpc.UnaryServerInterceptor) (interface{}, error) {
+	in := new(OwnershipAnnounce)
 	if err := dec(in); err != nil {
 		return nil, err
 	}
 	if interceptor == nil {
-		return srv.(ControlPlaneServer).ConfirmOwner(ctx, in)
+		return srv.(ControlPlaneServer).AnnounceOwnership(ctx, in)
 	}
 	info := &grpc.UnaryServerInfo{
 		Server:     srv,
-		FullMethod: ControlPlane_ConfirmOwner_FullMethodName,
+		FullMethod: ControlPlane_AnnounceOwnership_FullMethodName,
 	}
 	handler := func(ctx context.Context, req interface{}) (interface{}, error) {
-		return srv.(ControlPlaneServer).ConfirmOwner(ctx, req.(*OwnerChangeRequest))
+		return srv.(ControlPlaneServer).AnnounceOwnership(ctx, req.(*OwnershipAnnounce))
+	}
+	return interceptor(ctx, in, info, handler)
+}
+
+func _ControlPlane_AnnounceExpiry_Handler(srv interface{}, ctx context.Context, dec func(interface{}) error, interceptor grpc.UnaryServerInterceptor) (interface{}, error) {
+	in := new(ExpiryAnnounce)
+	if err := dec(in); err != nil {
+		return nil, err
+	}
+	if interceptor == nil {
+		return srv.(ControlPlaneServer).AnnounceExpiry(ctx, in)
+	}
+	info := &grpc.UnaryServerInfo{
+		Server:     srv,
+		FullMethod: ControlPlane_AnnounceExpiry_FullMethodName,
+	}
+	handler := func(ctx context.Context, req interface{}) (interface{}, error) {
+		return srv.(ControlPlaneServer).AnnounceExpiry(ctx, req.(*ExpiryAnnounce))
 	}
 	return interceptor(ctx, in, info, handler)
 }
@@ -274,8 +310,12 @@ var ControlPlane_ServiceDesc = grpc.ServiceDesc{
 			Handler:    _ControlPlane_GetCartIds_Handler,
 		},
 		{
-			MethodName: "ConfirmOwner",
-			Handler:    _ControlPlane_ConfirmOwner_Handler,
+			MethodName: "AnnounceOwnership",
+			Handler:    _ControlPlane_AnnounceOwnership_Handler,
+		},
+		{
+			MethodName: "AnnounceExpiry",
+			Handler:    _ControlPlane_AnnounceExpiry_Handler,
 		},
 		{
 			MethodName: "Closing",
@@ -283,5 +323,5 @@ var ControlPlane_ServiceDesc = grpc.ServiceDesc{
 		},
 	},
 	Streams:  []grpc.StreamDesc{},
-	Metadata: "control_plane.proto",
+	Metadata: "proto/control_plane.proto",
 }

proto/messages.pb.go

@@ -889,6 +889,102 @@ func (x *OrderCreated) GetStatus() string {
 	return ""
 }
 
+type Noop struct {
+	state         protoimpl.MessageState `protogen:"open.v1"`
+	unknownFields protoimpl.UnknownFields
+	sizeCache     protoimpl.SizeCache
+}
+
+func (x *Noop) Reset() {
+	*x = Noop{}
+	mi := &file_messages_proto_msgTypes[11]
+	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+	ms.StoreMessageInfo(mi)
+}
+
+func (x *Noop) String() string {
+	return protoimpl.X.MessageStringOf(x)
+}
+
+func (*Noop) ProtoMessage() {}
+
+func (x *Noop) ProtoReflect() protoreflect.Message {
+	mi := &file_messages_proto_msgTypes[11]
+	if x != nil {
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		if ms.LoadMessageInfo() == nil {
+			ms.StoreMessageInfo(mi)
+		}
+		return ms
+	}
+	return mi.MessageOf(x)
+}
+
+// Deprecated: Use Noop.ProtoReflect.Descriptor instead.
+func (*Noop) Descriptor() ([]byte, []int) {
+	return file_messages_proto_rawDescGZIP(), []int{11}
+}
+
+type InitializeCheckout struct {
+	state             protoimpl.MessageState `protogen:"open.v1"`
+	OrderId           string                 `protobuf:"bytes,1,opt,name=orderId,proto3" json:"orderId,omitempty"`
+	Status            string                 `protobuf:"bytes,2,opt,name=status,proto3" json:"status,omitempty"`
+	PaymentInProgress bool                   `protobuf:"varint,3,opt,name=paymentInProgress,proto3" json:"paymentInProgress,omitempty"`
+	unknownFields     protoimpl.UnknownFields
+	sizeCache         protoimpl.SizeCache
+}
+
+func (x *InitializeCheckout) Reset() {
+	*x = InitializeCheckout{}
+	mi := &file_messages_proto_msgTypes[12]
+	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+	ms.StoreMessageInfo(mi)
+}
+
+func (x *InitializeCheckout) String() string {
+	return protoimpl.X.MessageStringOf(x)
+}
+
+func (*InitializeCheckout) ProtoMessage() {}
+
+func (x *InitializeCheckout) ProtoReflect() protoreflect.Message {
+	mi := &file_messages_proto_msgTypes[12]
+	if x != nil {
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		if ms.LoadMessageInfo() == nil {
+			ms.StoreMessageInfo(mi)
+		}
+		return ms
+	}
+	return mi.MessageOf(x)
+}
+
+// Deprecated: Use InitializeCheckout.ProtoReflect.Descriptor instead.
+func (*InitializeCheckout) Descriptor() ([]byte, []int) {
+	return file_messages_proto_rawDescGZIP(), []int{12}
+}
+
+func (x *InitializeCheckout) GetOrderId() string {
+	if x != nil {
+		return x.OrderId
+	}
+	return ""
+}
+
+func (x *InitializeCheckout) GetStatus() string {
+	if x != nil {
+		return x.Status
+	}
+	return ""
+}
+
+func (x *InitializeCheckout) GetPaymentInProgress() bool {
+	if x != nil {
+		return x.PaymentInProgress
+	}
+	return false
+}
+
 var File_messages_proto protoreflect.FileDescriptor
 
 const file_messages_proto_rawDesc = "" +
@@ -997,8 +1093,12 @@ const file_messages_proto_rawDesc = "" +
 	"\acountry\x18\x06 \x01(\tR\acountry\"@\n" +
 	"\fOrderCreated\x12\x18\n" +
 	"\aorderId\x18\x01 \x01(\tR\aorderId\x12\x16\n" +
-	"\x06status\x18\x02 \x01(\tR\x06statusB\fZ\n" +
-	".;messagesb\x06proto3"
+	"\x06status\x18\x02 \x01(\tR\x06status\"\x06\n" +
+	"\x04Noop\"t\n" +
+	"\x12InitializeCheckout\x12\x18\n" +
+	"\aorderId\x18\x01 \x01(\tR\aorderId\x12\x16\n" +
+	"\x06status\x18\x02 \x01(\tR\x06status\x12,\n" +
+	"\x11paymentInProgress\x18\x03 \x01(\bR\x11paymentInProgressB.Z,git.tornberg.me/go-cart-actor/proto;messagesb\x06proto3"
 
 var (
 	file_messages_proto_rawDescOnce sync.Once
@@ -1012,7 +1112,7 @@ func file_messages_proto_rawDescGZIP() []byte {
 	return file_messages_proto_rawDescData
 }
 
-var file_messages_proto_msgTypes = make([]protoimpl.MessageInfo, 11)
+var file_messages_proto_msgTypes = make([]protoimpl.MessageInfo, 13)
 var file_messages_proto_goTypes = []any{
 	(*AddRequest)(nil),          // 0: messages.AddRequest
 	(*SetCartRequest)(nil),      // 1: messages.SetCartRequest
@@ -1025,6 +1125,8 @@ var file_messages_proto_goTypes = []any{
 	(*RemoveDelivery)(nil),      // 8: messages.RemoveDelivery
 	(*CreateCheckoutOrder)(nil), // 9: messages.CreateCheckoutOrder
 	(*OrderCreated)(nil),        // 10: messages.OrderCreated
+	(*Noop)(nil),                // 11: messages.Noop
+	(*InitializeCheckout)(nil),  // 12: messages.InitializeCheckout
 }
 var file_messages_proto_depIdxs = []int32{
 	0, // 0: messages.SetCartRequest.items:type_name -> messages.AddRequest
@@ -1052,7 +1154,7 @@ func file_messages_proto_init() {
 			GoPackagePath: reflect.TypeOf(x{}).PkgPath(),
 			RawDescriptor: unsafe.Slice(unsafe.StringData(file_messages_proto_rawDesc), len(file_messages_proto_rawDesc)),
 			NumEnums:      0,
-			NumMessages:   11,
+			NumMessages:   13,
 			NumExtensions: 0,
 			NumServices:   0,
 		},

proto/messages.proto

@@ -1,6 +1,6 @@
 syntax = "proto3";
 package messages;
-option go_package = ".;messages";
+option go_package = "git.tornberg.me/go-cart-actor/proto;messages";
 
 message AddRequest {
 		int32 quantity = 1;
@@ -93,3 +93,13 @@ message OrderCreated {
 		string orderId = 1;
 		string status = 2;
 }
+
+message Noop {
+		// Intentionally empty - used for ownership acquisition or health pings
+}
+
+message InitializeCheckout {
+        string orderId = 1;
+        string status = 2;
+        bool paymentInProgress = 3;
+}

remote-grain-pool._go

@@ -1,67 +0,0 @@
-// package main
-
-// import "sync"
-
-// type RemoteGrainPool struct {
-// 	mu     sync.RWMutex
-// 	Host   string
-// 	grains map[CartId]*RemoteGrain
-// }
-
-// func NewRemoteGrainPool(addr string) *RemoteGrainPool {
-// 	return &RemoteGrainPool{
-// 		Host:   addr,
-// 		grains: make(map[CartId]*RemoteGrain),
-// 	}
-// }
-
-// func (p *RemoteGrainPool) findRemoteGrain(id CartId) *RemoteGrain {
-// 	p.mu.RLock()
-// 	grain, ok := p.grains[id]
-// 	p.mu.RUnlock()
-// 	if !ok {
-// 		return nil
-// 	}
-// 	return grain
-// }
-
-// func (p *RemoteGrainPool) findOrCreateGrain(id CartId) (*RemoteGrain, error) {
-// 	grain := p.findRemoteGrain(id)
-
-// 	if grain == nil {
-// 		grain, err := NewRemoteGrain(id, p.Host)
-// 		if err != nil {
-// 			return nil, err
-// 		}
-// 		p.mu.Lock()
-// 		p.grains[id] = grain
-// 		p.mu.Unlock()
-// 	}
-// 	return grain, nil
-// }
-
-// func (p *RemoteGrainPool) Delete(id CartId) {
-// 	p.mu.Lock()
-// 	delete(p.grains, id)
-// 	p.mu.Unlock()
-// }
-
-// func (p *RemoteGrainPool) Process(id CartId, messages ...Message) (*FrameWithPayload, error) {
-// 	var result *FrameWithPayload
-// 	grain, err := p.findOrCreateGrain(id)
-// 	if err != nil {
-// 		return nil, err
-// 	}
-// 	for _, message := range messages {
-// 		result, err = grain.HandleMessage(&message, false)
-// 	}
-// 	return result, err
-// }
-
-// func (p *RemoteGrainPool) Get(id CartId) (*FrameWithPayload, error) {
-// 	grain, err := p.findOrCreateGrain(id)
-// 	if err != nil {
-// 		return nil, err
-// 	}
-// 	return grain.GetCurrentState()
-// }

remote_grain_grpc.go

@@ -1,147 +0,0 @@
-package main
-
-import (
-	"bytes"
-	"context"
-	"fmt"
-	"log"
-	"time"
-
-	proto "git.tornberg.me/go-cart-actor/proto" // generated package name is 'messages'; aliased as proto for consistency
-	"google.golang.org/grpc"
-)
-
-// RemoteGrainGRPC is the gRPC-backed implementation of a remote grain.
-// It mirrors the previous RemoteGrain (TCP/frame based) while using the
-// new CartActor gRPC service. It implements the Grain interface so that
-// SyncedPool can remain largely unchanged when swapping transport layers.
-type RemoteGrainGRPC struct {
-	Id     CartId
-	Host   string
-	client proto.CartActorClient
-	// Optional: keep the underlying conn so higher-level code can close if needed
-	conn *grpc.ClientConn
-
-	// Per-call timeout settings (tunable)
-	mutateTimeout time.Duration
-	stateTimeout  time.Duration
-}
-
-// NewRemoteGrainGRPC constructs a remote grain adapter from an existing gRPC client.
-func NewRemoteGrainGRPC(id CartId, host string, client proto.CartActorClient) *RemoteGrainGRPC {
-	return &RemoteGrainGRPC{
-		Id:            id,
-		Host:          host,
-		client:        client,
-		mutateTimeout: 800 * time.Millisecond,
-		stateTimeout:  400 * time.Millisecond,
-	}
-}
-
-// NewRemoteGrainGRPCWithConn dials the target and creates the gRPC client.
-// target should be host:port (where the CartActor service is exposed).
-func NewRemoteGrainGRPCWithConn(id CartId, host string, target string, dialOpts ...grpc.DialOption) (*RemoteGrainGRPC, error) {
-	// NOTE: insecure for initial migration; should be replaced with TLS later.
-	baseOpts := []grpc.DialOption{grpc.WithInsecure(), grpc.WithBlock()}
-	baseOpts = append(baseOpts, dialOpts...)
-
-	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
-	defer cancel()
-
-	conn, err := grpc.DialContext(ctx, target, baseOpts...)
-	if err != nil {
-		return nil, err
-	}
-
-	client := proto.NewCartActorClient(conn)
-	return &RemoteGrainGRPC{
-		Id:            id,
-		Host:          host,
-		client:        client,
-		conn:          conn,
-		mutateTimeout: 800 * time.Millisecond,
-		stateTimeout:  400 * time.Millisecond,
-	}, nil
-}
-
-func (g *RemoteGrainGRPC) GetId() CartId {
-	return g.Id
-}
-
-// HandleMessage serializes the underlying mutation proto (without legacy message header)
-// and invokes the CartActor.Mutate RPC. It wraps the reply into a FrameWithPayload
-// for compatibility with existing higher-level code paths.
-func (g *RemoteGrainGRPC) HandleMessage(message *Message, isReplay bool) (*FrameWithPayload, error) {
-	if message == nil {
-		return nil, fmt.Errorf("nil message")
-	}
-	if isReplay {
-		// Remote replay not expected; ignore to keep parity with old implementation.
-		return nil, fmt.Errorf("replay not supported for remote grains")
-	}
-
-	handler, err := GetMessageHandler(message.Type)
-	if err != nil {
-		return nil, err
-	}
-
-	// Ensure timestamp set (legacy behavior)
-	if message.TimeStamp == nil {
-		ts := time.Now().Unix()
-		message.TimeStamp = &ts
-	}
-
-	// Marshal underlying proto payload only (no StorableMessageHeader)
-	var buf bytes.Buffer
-	err = handler.Write(message, &buf)
-	if err != nil {
-		return nil, fmt.Errorf("encode mutation payload: %w", err)
-	}
-
-	req := &proto.MutationRequest{
-		CartId:          g.Id.String(),
-		Type:            proto.MutationType(message.Type), // numeric mapping preserved
-		Payload:         buf.Bytes(),
-		ClientTimestamp: *message.TimeStamp,
-	}
-
-	ctx, cancel := context.WithTimeout(context.Background(), g.mutateTimeout)
-	defer cancel()
-
-	resp, err := g.client.Mutate(ctx, req)
-	if err != nil {
-		return nil, err
-	}
-
-	frame := MakeFrameWithPayload(RemoteHandleMutationReply, StatusCode(resp.StatusCode), resp.Payload)
-	return &frame, nil
-}
-
-// GetCurrentState calls CartActor.GetState and returns a FrameWithPayload
-// shaped like the legacy RemoteGetStateReply.
-func (g *RemoteGrainGRPC) GetCurrentState() (*FrameWithPayload, error) {
-	ctx, cancel := context.WithTimeout(context.Background(), g.stateTimeout)
-	defer cancel()
-
-	resp, err := g.client.GetState(ctx, &proto.StateRequest{
-		CartId: g.Id.String(),
-	})
-	if err != nil {
-		return nil, err
-	}
-	frame := MakeFrameWithPayload(RemoteGetStateReply, StatusCode(resp.StatusCode), resp.Payload)
-	return &frame, nil
-}
-
-// Close closes the underlying gRPC connection if this adapter created it.
-func (g *RemoteGrainGRPC) Close() error {
-	if g.conn != nil {
-		return g.conn.Close()
-	}
-	return nil
-}
-
-// Debug helper to log operations (optional).
-func (g *RemoteGrainGRPC) logf(format string, args ...interface{}) {
-	log.Printf("[remote-grain-grpc host=%s id=%s] %s", g.Host, g.Id.String(), fmt.Sprintf(format, args...))
-}

synced-pool.go

@@ -1,473 +0,0 @@
-package main
-
-import (
-	"context"
-	"fmt"
-	"log"
-	"sync"
-	"time"
-
-	proto "git.tornberg.me/go-cart-actor/proto"
-	"github.com/prometheus/client_golang/prometheus"
-	"github.com/prometheus/client_golang/prometheus/promauto"
-	"google.golang.org/grpc"
-	"k8s.io/apimachinery/pkg/watch"
-)
-
-// SyncedPool coordinates cart grain ownership across nodes using gRPC control plane
-// and cart actor services. Legacy frame / TCP code has been removed.
-//
-// Responsibilities:
-//   - Local grain access (delegates to GrainLocalPool)
-//   - Remote grain proxy management (RemoteGrainGRPC)
-//   - Cluster membership (AddRemote via discovery + negotiation)
-//   - Ownership acquisition (quorum via ConfirmOwner RPC)
-//   - Health/ping monitoring & remote removal
-//
-// Thread-safety: public methods that mutate internal maps lock p.mu (RWMutex).
-type SyncedPool struct {
-	Hostname string
-	local    *GrainLocalPool
-
-	mu sync.RWMutex
-
-	// Remote host state (gRPC only)
-	remoteHosts map[string]*RemoteHostGRPC // host -> remote host
-
-	// Remote grain proxies (by cart id)
-	remoteIndex map[CartId]Grain
-
-	// Discovery handler for re-adding hosts after failures
-	discardedHostHandler *DiscardedHostHandler
-
-	// Metrics / instrumentation dependencies already declared globally
-}
-
-// RemoteHostGRPC tracks a remote host's clients & health.
-type RemoteHostGRPC struct {
-	Host          string
-	Conn          *grpc.ClientConn
-	CartClient    proto.CartActorClient
-	ControlClient proto.ControlPlaneClient
-	MissedPings   int
-}
-
-func (r *RemoteHostGRPC) IsHealthy() bool {
-	return r.MissedPings < 3
-}
-
-var (
-	negotiationCount = promauto.NewCounter(prometheus.CounterOpts{
-		Name: "cart_remote_negotiation_total",
-		Help: "The total number of remote negotiations",
-	})
-	grainSyncCount = promauto.NewCounter(prometheus.CounterOpts{
-		Name: "cart_grain_sync_total",
-		Help: "The total number of grain owner changes",
-	})
-	connectedRemotes = promauto.NewGauge(prometheus.GaugeOpts{
-		Name: "cart_connected_remotes",
-		Help: "The number of connected remotes",
-	})
-	remoteLookupCount = promauto.NewCounter(prometheus.CounterOpts{
-		Name: "cart_remote_lookup_total",
-		Help: "The total number of remote lookups",
-	})
-)
-
-func NewSyncedPool(local *GrainLocalPool, hostname string, discovery Discovery) (*SyncedPool, error) {
-	p := &SyncedPool{
-		Hostname:             hostname,
-		local:                local,
-		remoteHosts:          make(map[string]*RemoteHostGRPC),
-		remoteIndex:          make(map[CartId]Grain),
-		discardedHostHandler: NewDiscardedHostHandler(1338),
-	}
-	p.discardedHostHandler.SetReconnectHandler(p.AddRemote)
-
-	if discovery != nil {
-		go func() {
-			time.Sleep(3 * time.Second) // allow gRPC server startup
-			log.Printf("Starting discovery watcher")
-			ch, err := discovery.Watch()
-			if err != nil {
-				log.Printf("Discovery error: %v", err)
-				return
-			}
-			for evt := range ch {
-				if evt.Host == "" {
-					continue
-				}
-				switch evt.Type {
-				case watch.Deleted:
-					if p.IsKnown(evt.Host) {
-						p.RemoveHost(evt.Host)
-					}
-				default:
-					if !p.IsKnown(evt.Host) {
-						log.Printf("Discovered host %s", evt.Host)
-						p.AddRemote(evt.Host)
-					}
-				}
-			}
-		}()
-	} else {
-		log.Printf("No discovery configured; expecting manual AddRemote or static host injection")
-	}
-
-	return p, nil
-}
-
-// ------------------------- Remote Host Management -----------------------------
-
-// AddRemote dials a remote host and initializes grain proxies.
-func (p *SyncedPool) AddRemote(host string) {
-	if host == "" || host == p.Hostname {
-		return
-	}
-
-	p.mu.Lock()
-	if _, exists := p.remoteHosts[host]; exists {
-		p.mu.Unlock()
-		return
-	}
-	p.mu.Unlock()
-
-	target := fmt.Sprintf("%s:1337", host)
-	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
-	defer cancel()
-	conn, err := grpc.DialContext(ctx, target, grpc.WithInsecure(), grpc.WithBlock())
-	if err != nil {
-		log.Printf("AddRemote: dial %s failed: %v", target, err)
-		return
-	}
-
-	cartClient := proto.NewCartActorClient(conn)
-	controlClient := proto.NewControlPlaneClient(conn)
-
-	// Health check (Ping) with limited retries
-	pings := 3
-	for pings > 0 {
-		ctxPing, cancelPing := context.WithTimeout(context.Background(), 1*time.Second)
-		_, pingErr := controlClient.Ping(ctxPing, &proto.Empty{})
-		cancelPing()
-		if pingErr == nil {
-			break
-		}
-		pings--
-		time.Sleep(200 * time.Millisecond)
-		if pings == 0 {
-			log.Printf("AddRemote: ping %s failed after retries: %v", host, pingErr)
-			conn.Close()
-			return
-		}
-	}
-
-	remote := &RemoteHostGRPC{
-		Host:          host,
-		Conn:          conn,
-		CartClient:    cartClient,
-		ControlClient: controlClient,
-		MissedPings:   0,
-	}
-
-	p.mu.Lock()
-	p.remoteHosts[host] = remote
-	p.mu.Unlock()
-	connectedRemotes.Set(float64(p.RemoteCount()))
-
-	log.Printf("Connected to remote host %s", host)
-
-	go p.pingLoop(remote)
-	go p.initializeRemote(remote)
-	go p.Negotiate()
-}
-
-// initializeRemote fetches remote cart ids and sets up remote grain proxies.
-func (p *SyncedPool) initializeRemote(remote *RemoteHostGRPC) {
-	ctx, cancel := context.WithTimeout(context.Background(), 3*time.Second)
-	defer cancel()
-	reply, err := remote.ControlClient.GetCartIds(ctx, &proto.Empty{})
-	if err != nil {
-		log.Printf("Init remote %s: GetCartIds error: %v", remote.Host, err)
-		return
-	}
-	count := 0
-	for _, idStr := range reply.CartIds {
-		if idStr == "" {
-			continue
-		}
-		p.SpawnRemoteGrain(ToCartId(idStr), remote.Host)
-		count++
-	}
-	log.Printf("Remote %s reported %d grains", remote.Host, count)
-}
-
-// RemoveHost removes remote host and its grains.
-func (p *SyncedPool) RemoveHost(host string) {
-	p.mu.Lock()
-	remote, exists := p.remoteHosts[host]
-	if exists {
-		delete(p.remoteHosts, host)
-	}
-	// remove grains pointing to host
-	for id, g := range p.remoteIndex {
-		if rg, ok := g.(*RemoteGrainGRPC); ok && rg.Host == host {
-			delete(p.remoteIndex, id)
-		}
-	}
-	p.mu.Unlock()
-
-	if exists {
-		remote.Conn.Close()
-	}
-	connectedRemotes.Set(float64(p.RemoteCount()))
-}
-
-// RemoteCount returns number of tracked remote hosts.
-func (p *SyncedPool) RemoteCount() int {
-	p.mu.RLock()
-	defer p.mu.RUnlock()
-	return len(p.remoteHosts)
-}
-
-func (p *SyncedPool) IsKnown(host string) bool {
-	if host == p.Hostname {
-		return true
-	}
-	p.mu.RLock()
-	defer p.mu.RUnlock()
-	_, ok := p.remoteHosts[host]
-	return ok
-}
-
-func (p *SyncedPool) ExcludeKnown(hosts []string) []string {
-	ret := make([]string, 0, len(hosts))
-	for _, h := range hosts {
-		if !p.IsKnown(h) {
-			ret = append(ret, h)
-		}
-	}
-	return ret
-}
-
-// ------------------------- Health / Ping -------------------------------------
-
-func (p *SyncedPool) pingLoop(remote *RemoteHostGRPC) {
-	ticker := time.NewTicker(3 * time.Second)
-	defer ticker.Stop()
-	for range ticker.C {
-		ctx, cancel := context.WithTimeout(context.Background(), 1*time.Second)
-		_, err := remote.ControlClient.Ping(ctx, &proto.Empty{})
-		cancel()
-		if err != nil {
-			remote.MissedPings++
-			log.Printf("Ping %s failed (%d)", remote.Host, remote.MissedPings)
-			if !remote.IsHealthy() {
-				log.Printf("Remote %s unhealthy, removing", remote.Host)
-				p.RemoveHost(remote.Host)
-				return
-			}
-			continue
-		}
-		remote.MissedPings = 0
-	}
-}
-
-func (p *SyncedPool) IsHealthy() bool {
-	p.mu.RLock()
-	defer p.mu.RUnlock()
-	for _, r := range p.remoteHosts {
-		if !r.IsHealthy() {
-			return false
-		}
-	}
-	return true
-}
-
-// ------------------------- Negotiation ---------------------------------------
-
-func (p *SyncedPool) Negotiate() {
-	negotiationCount.Inc()
-
-	p.mu.RLock()
-	hosts := make([]string, 0, len(p.remoteHosts)+1)
-	hosts = append(hosts, p.Hostname)
-	for h := range p.remoteHosts {
-		hosts = append(hosts, h)
-	}
-	remotes := make([]*RemoteHostGRPC, 0, len(p.remoteHosts))
-	for _, r := range p.remoteHosts {
-		remotes = append(remotes, r)
-	}
-	p.mu.RUnlock()
-
-	for _, r := range remotes {
-		ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
-		reply, err := r.ControlClient.Negotiate(ctx, &proto.NegotiateRequest{KnownHosts: hosts})
-		cancel()
-		if err != nil {
-			log.Printf("Negotiate with %s failed: %v", r.Host, err)
-			continue
-		}
-		for _, h := range reply.Hosts {
-			if !p.IsKnown(h) {
-				p.AddRemote(h)
-			}
-		}
-	}
-}
-
-// ------------------------- Grain Management ----------------------------------
-
-// RemoveRemoteGrain removes a remote grain mapping.
-func (p *SyncedPool) RemoveRemoteGrain(id CartId) {
-	p.mu.Lock()
-	delete(p.remoteIndex, id)
-	p.mu.Unlock()
-}
-
-// SpawnRemoteGrain creates/updates a remote grain proxy for a given host.
-func (p *SyncedPool) SpawnRemoteGrain(id CartId, host string) {
-	if id.String() == "" {
-		return
-	}
-	p.mu.Lock()
-	// If local grain exists, remove it (ownership changed)
-	if g, ok := p.local.grains[id]; ok && g != nil {
-		delete(p.local.grains, id)
-	}
-	remoteHost, ok := p.remoteHosts[host]
-	if !ok {
-		p.mu.Unlock()
-		log.Printf("SpawnRemoteGrain: host %s unknown (id=%s), attempting AddRemote", host, id)
-		go p.AddRemote(host)
-		return
-	}
-	rg := NewRemoteGrainGRPC(id, host, remoteHost.CartClient)
-	p.remoteIndex[id] = rg
-	p.mu.Unlock()
-}
-
-// GetHealthyRemotes returns a copy slice of healthy remote hosts.
-func (p *SyncedPool) GetHealthyRemotes() []*RemoteHostGRPC {
-	p.mu.RLock()
-	defer p.mu.RUnlock()
-	ret := make([]*RemoteHostGRPC, 0, len(p.remoteHosts))
-	for _, r := range p.remoteHosts {
-		if r.IsHealthy() {
-			ret = append(ret, r)
-		}
-	}
-	return ret
-}
-
-// RequestOwnership attempts to become owner of a cart, requiring quorum.
-// On success local grain is (or will be) created; peers spawn remote proxies.
-func (p *SyncedPool) RequestOwnership(id CartId) error {
-	ok := 0
-	all := 0
-	remotes := p.GetHealthyRemotes()
-	for _, r := range remotes {
-		ctx, cancel := context.WithTimeout(context.Background(), 800*time.Millisecond)
-		reply, err := r.ControlClient.ConfirmOwner(ctx, &proto.OwnerChangeRequest{
-			CartId:  id.String(),
-			NewHost: p.Hostname,
-		})
-		cancel()
-		all++
-		if err != nil || reply == nil || !reply.Accepted {
-			log.Printf("ConfirmOwner failure from %s for %s: %v (reply=%v)", r.Host, id, err, reply)
-			continue
-		}
-		ok++
-	}
-
-	// Quorum rule mirrors legacy:
-	//  - If fewer than 3 total, require all.
-	//  - Else require majority (ok >= all/2).
-	if (all < 3 && ok < all) || ok < (all/2) {
-		p.removeLocalGrain(id)
-		return fmt.Errorf("quorum not reached (ok=%d all=%d)", ok, all)
-	}
-	grainSyncCount.Inc()
-	return nil
-}
-
-func (p *SyncedPool) removeLocalGrain(id CartId) {
-	p.mu.Lock()
-	delete(p.local.grains, id)
-	p.mu.Unlock()
-}
-
-// getGrain returns a local or remote grain; if absent, attempts ownership.
-func (p *SyncedPool) getGrain(id CartId) (Grain, error) {
-	p.mu.RLock()
-	localGrain, isLocal := p.local.grains[id]
-	remoteGrain, isRemote := p.remoteIndex[id]
-	p.mu.RUnlock()
-
-	if isLocal && localGrain != nil {
-		return localGrain, nil
-	}
-	if isRemote {
-		remoteLookupCount.Inc()
-		return remoteGrain, nil
-	}
-
-	// Attempt to claim ownership (async semantics preserved)
-	go p.RequestOwnership(id)
-
-	// Create local grain (lazy spawn) - may be rolled back by quorum failure
-	grain, err := p.local.GetGrain(id)
-	if err != nil {
-		return nil, err
-	}
-	return grain, nil
-}
-
-// Process applies mutation(s) to a grain (local or remote).
-func (p *SyncedPool) Process(id CartId, messages ...Message) (*FrameWithPayload, error) {
-	grain, err := p.getGrain(id)
-	if err != nil {
-		return nil, err
-	}
-	var res *FrameWithPayload
-	for _, m := range messages {
-		res, err = grain.HandleMessage(&m, false)
-		if err != nil {
-			return nil, err
-		}
-	}
-	return res, nil
-}
-
-// Get returns current state of a grain (local or remote).
-func (p *SyncedPool) Get(id CartId) (*FrameWithPayload, error) {
-	grain, err := p.getGrain(id)
-	if err != nil {
-		return nil, err
-	}
-	return grain.GetCurrentState()
-}
-
-// Close notifies remotes this host is terminating.
-func (p *SyncedPool) Close() {
-	p.mu.RLock()
-	remotes := make([]*RemoteHostGRPC, 0, len(p.remoteHosts))
-	for _, r := range p.remoteHosts {
-		remotes = append(remotes, r)
-	}
-	p.mu.RUnlock()
-
-	for _, r := range remotes {
-		go func(rh *RemoteHostGRPC) {
-			ctx, cancel := context.WithTimeout(context.Background(), 1*time.Second)
-			_, err := rh.ControlClient.Closing(ctx, &proto.ClosingNotice{Host: p.Hostname})
-			cancel()
-			if err != nil {
-				log.Printf("Close notify to %s failed: %v", rh.Host, err)
-			}
-		}(r)
-	}
-}

tcp-connection_test.go

@@ -1,8 +0,0 @@
-/*
-Legacy TCP networking (GenericListener / Frame protocol) has been removed
-as part of the gRPC migration. This file intentionally contains no tests.
-
-Keeping an empty Go file (with a package declaration) ensures the old
-tcp-connection test target no longer runs without causing build issues.
-*/
-package main