Complete refactor to new grpc control plane and only http proxy for carts (#4)

Co-authored-by: matst80 <mats.tornberg@gmail.com>
Reviewed-on: https://git.tornberg.me/mats/go-cart-actor/pulls/4
Co-authored-by: Mats Törnberg <mats@tornberg.me>
Co-committed-by: Mats Törnberg <mats@tornberg.me>

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 ./cmd/cart
+
+############################
+# 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"]