implement redis inventory with threadsafe reservation

cmd/inventory/main.go

@@ -0,0 +1,54 @@
+package main
+
+import (
+	"context"
+	"log"
+
+	"git.tornberg.me/go-cart-actor/pkg/inventory"
+	"github.com/redis/go-redis/v9"
+	"github.com/redis/go-redis/v9/maintnotifications"
+)
+
+func main() {
+	var ctx = context.Background()
+	rdb := redis.NewClient(&redis.Options{
+		Addr:     "10.10.3.18:6379",
+		Password: "slaskredis", // no password set
+		DB:       0,            // use default DB
+		MaintNotificationsConfig: &maintnotifications.Config{
+			Mode: maintnotifications.ModeDisabled,
+		},
+	})
+	s, err := inventory.NewRedisInventoryService(rdb, ctx)
+	if err != nil {
+		log.Fatalf("Unable to connect to inventory redis", err)
+		return
+	}
+	rdb.Pipelined(ctx, func(p redis.Pipeliner) error {
+		s.UpdateInventory(p, "1", "1", 10)
+		s.UpdateInventory(p, "2", "2", 20)
+		s.UpdateInventory(p, "3", "3", 30)
+		s.UpdateInventory(p, "4", "4", 40)
+		return nil
+	})
+	err = s.ReserveInventory(inventory.ReserveRequest{
+		SKU:        "1",
+		LocationID: "1",
+		Quantity:   3,
+	}, inventory.ReserveRequest{
+		SKU:        "2",
+		LocationID: "2",
+		Quantity:   15,
+	})
+	if err != nil {
+		log.Printf("Unable to reserve inventory: %v", err)
+		return
+	}
+	v, err := s.GetInventory("1", "1")
+	if err != nil {
+		log.Printf("Unable to get inventory: %v", err)
+		return
+	}
+	log.Printf("Inventory after reservation: %v", v)
+
+}

go.mod

@@ -8,6 +8,7 @@ require (
 	github.com/matst80/slask-finder v0.0.0-20251023104024-f788e5a51d68
 	github.com/prometheus/client_golang v1.23.2
 	github.com/rabbitmq/amqp091-go v1.10.0
+	github.com/redis/go-redis/v9 v9.16.0
 	google.golang.org/grpc v1.76.0
 	google.golang.org/protobuf v1.36.10
 	k8s.io/api v0.34.1
@@ -21,6 +22,7 @@ require (
 	github.com/bits-and-blooms/bitset v1.24.1 // indirect
 	github.com/cespare/xxhash/v2 v2.3.0 // indirect
 	github.com/davecgh/go-spew v1.1.2-0.20180830191138-d8f796af33cc // indirect
+	github.com/dgryski/go-rendezvous v0.0.0-20200823014737-9f7001d12a5f // indirect
 	github.com/dprotaso/go-yit v0.0.0-20220510233725-9ba8df137936 // indirect
 	github.com/emicklei/go-restful/v3 v3.13.0 // indirect
 	github.com/fxamacker/cbor/v2 v2.9.0 // indirect

go.sum

@@ -4,6 +4,10 @@ github.com/beorn7/perks v1.0.1 h1:VlbKKnNfV8bJzeqoa4cOKqO6bYr3WgKZxO8Z16+hsOM=
 github.com/beorn7/perks v1.0.1/go.mod h1:G2ZrVWU2WbWT9wwq4/hrbKbnv/1ERSJQ0ibhJ6rlkpw=
 github.com/bits-and-blooms/bitset v1.24.1 h1:hqnfFbjjk3pxGa5E9Ho3hjoU7odtUuNmJ9Ao+Bo8s1c=
 github.com/bits-and-blooms/bitset v1.24.1/go.mod h1:7hO7Gc7Pp1vODcmWvKMRA9BNmbv6a/7QIWpPxHddWR8=
+github.com/bsm/ginkgo/v2 v2.12.0 h1:Ny8MWAHyOepLGlLKYmXG4IEkioBysk6GpaRTLC8zwWs=
+github.com/bsm/ginkgo/v2 v2.12.0/go.mod h1:SwYbGRRDovPVboqFv0tPTcG1sN61LM1Z4ARdbAV9g4c=
+github.com/bsm/gomega v1.27.10 h1:yeMWxP2pV2fG3FgAODIY8EiRE3dy0aeFYt4l7wh6yKA=
+github.com/bsm/gomega v1.27.10/go.mod h1:JyEr/xRbxbtgWNi8tIEVPUYZ5Dzef52k01W3YH0H+O0=
 github.com/cespare/xxhash/v2 v2.3.0 h1:UL815xU9SqsFlibzuggzjXhog7bL6oX9BbNZnL2UFvs=
 github.com/cespare/xxhash/v2 v2.3.0/go.mod h1:VGX0DQ3Q6kWi7AoAeZDth3/j3BFtOZR5XLFGgcrjCOs=
 github.com/chzyer/logex v1.1.10/go.mod h1:+Ywpsq7O8HXn0nuIou7OrIPyXbp3wmkHB+jjWRnGsAI=
@@ -13,6 +17,8 @@ github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSs
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.2-0.20180830191138-d8f796af33cc h1:U9qPSI2PIWSS1VwoXQT9A3Wy9MM3WgvqSxFWenqJduM=
 github.com/davecgh/go-spew v1.1.2-0.20180830191138-d8f796af33cc/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/dgryski/go-rendezvous v0.0.0-20200823014737-9f7001d12a5f h1:lO4WD4F/rVNCu3HqELle0jiPLLBs70cWOduZpkS1E78=
+github.com/dgryski/go-rendezvous v0.0.0-20200823014737-9f7001d12a5f/go.mod h1:cuUVRXasLTGF7a8hSLbxyZXjz+1KgoB3wDUb6vlszIc=
 github.com/dprotaso/go-yit v0.0.0-20191028211022-135eb7262960/go.mod h1:9HQzr9D/0PGwMEbC3d5AB7oi67+h4TsQqItC1GVYG58=
 github.com/dprotaso/go-yit v0.0.0-20220510233725-9ba8df137936 h1:PRxIJD8XjimM5aTknUK9w6DHLDox2r2M3DI4i2pnd3w=
 github.com/dprotaso/go-yit v0.0.0-20220510233725-9ba8df137936/go.mod h1:ttYvX5qlB+mlV1okblJqcSMtR4c52UKxDiX9GRBS8+Q=
@@ -168,6 +174,8 @@ github.com/prometheus/procfs v0.18.0 h1:2QTA9cKdznfYJz7EDaa7IiJobHuV7E1WzeBwcrhk
 github.com/prometheus/procfs v0.18.0/go.mod h1:M0aotyiemPhBCM0z5w87kL22CxfcH05ZpYlu+b4J7mw=
 github.com/rabbitmq/amqp091-go v1.10.0 h1:STpn5XsHlHGcecLmMFCtg7mqq0RnD+zFr4uzukfVhBw=
 github.com/rabbitmq/amqp091-go v1.10.0/go.mod h1:Hy4jKW5kQART1u+JkDTF9YYOQUHXqMuhrgxOEeS7G4o=
+github.com/redis/go-redis/v9 v9.16.0 h1:OotgqgLSRCmzfqChbQyG1PHC3tLNR89DG4jdOERSEP4=
+github.com/redis/go-redis/v9 v9.16.0/go.mod h1:u410H11HMLoB+TP67dz8rL9s6QW2j76l0//kSOd3370=
 github.com/rogpeppe/go-internal v1.13.1 h1:KvO1DLK/DRN07sQ1LQKScxyZJuNnedQ5/wKSR38lUII=
 github.com/rogpeppe/go-internal v1.13.1/go.mod h1:uMEvuHeurkdAXX61udpOXGD/AzZDWNMNyH2VO9fmH0o=
 github.com/sergi/go-diff v1.1.0 h1:we8PVUC3FE2uYfodKH/nBHMSetSfHDR6scGdBi+erh0=

pkg/actor/mutation_registry_test.go

@@ -21,8 +21,8 @@ func TestRegisteredMutationBasics(t *testing.T) {
 		func(state *cartState, msg *messages.AddItem) error {
 			state.calls++
 			// copy to avoid external mutation side-effects (not strictly necessary for the test)
-			cp := *msg
-			state.lastAdded = &cp
+			cp := msg
+			state.lastAdded = cp
 			return nil
 		},
 		func() *messages.AddItem { return &messages.AddItem{} },

pkg/inventory/memory_service.go

@@ -0,0 +1,47 @@
+package inventory
+
+import (
+	"errors"
+	"sync"
+)
+
+type MemoryInventoryService struct {
+	warehouses map[LocationID]*Warehouse
+	mu         sync.RWMutex
+}
+
+func NewMemoryInventoryService() *MemoryInventoryService {
+	return &MemoryInventoryService{
+		warehouses: make(map[LocationID]*Warehouse),
+	}
+}
+
+func (s *MemoryInventoryService) AddWarehouse(warehouse *Warehouse) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	s.warehouses[warehouse.ID] = warehouse
+}
+
+func (s *MemoryInventoryService) GetInventory(sku SKU, locationID LocationID) (*InventoryItem, error) {
+	s.mu.RLock()
+	defer s.mu.RUnlock()
+
+	warehouse, ok := s.warehouses[locationID]
+	if !ok {
+		return nil, errors.New("warehouse not found")
+	}
+
+	for _, item := range warehouse.Inventory {
+		if item.SKU == sku {
+			return &item, nil
+		}
+	}
+	return nil, errors.New("sku not found in warehouse")
+}
+
+func (s *MemoryInventoryService) ReserveInventory(req ...ReserveRequest) error {
+	// We'll implement the reservation logic using Lua script execution here
+
+	// For now, let's just return an error indicating it's not implemented
+	return errors.New("reservation not implemented yet")
+}

pkg/inventory/redis_service.go

@@ -0,0 +1,180 @@
+package inventory
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"strconv"
+
+	"github.com/redis/go-redis/v9"
+)
+
+type RedisInventoryService struct {
+	client     *redis.Client
+	ctx        context.Context
+	luaScripts map[string]*redis.Script
+}
+
+func NewRedisInventoryService(client *redis.Client, ctx context.Context) (*RedisInventoryService, error) {
+	rdb := client
+
+	// Ping Redis to check connection
+	_, err := rdb.Ping(ctx).Result()
+	if err != nil {
+		return nil, err
+	}
+
+	return &RedisInventoryService{
+		client:     rdb,
+		ctx:        ctx,
+		luaScripts: make(map[string]*redis.Script),
+	}, nil
+}
+
+func (s *RedisInventoryService) LoadLuaScript(key string) error {
+	// Get the script from Redis
+	script, err := s.client.Get(s.ctx, key).Result()
+	if err != nil {
+		return err
+	}
+
+	// Load the script into the luaScripts cache
+	s.luaScripts[key] = redis.NewScript(script)
+	return nil
+}
+
+func (s *RedisInventoryService) AddWarehouse(warehouse *Warehouse) error {
+	// Convert warehouse to Redis-friendly format
+	data := map[string]interface{}{
+		"id":        string(warehouse.ID),
+		"name":      warehouse.Name,
+		"inventory": warehouse.Inventory,
+	}
+
+	// Store in Redis with a key pattern like "warehouse:<ID>"
+	key := "warehouse:" + string(warehouse.ID)
+	_, err := s.client.HMSet(s.ctx, key, data).Result()
+	return err
+}
+
+func (s *RedisInventoryService) GetInventory(sku SKU, locationID LocationID) (int64, error) {
+
+	cmd := s.client.Get(s.ctx, getInventoryKey(sku, locationID))
+	if err := cmd.Err(); err != nil {
+		return 0, err
+	}
+
+	i, err := cmd.Int64()
+	if err != nil {
+		return 0, err
+	}
+
+	return i, nil
+}
+
+func getInventoryKey(sku SKU, locationID LocationID) string {
+	return fmt.Sprintf("inventory:%s:%s", sku, locationID)
+}
+
+func (s *RedisInventoryService) UpdateInventory(rdb redis.Pipeliner, sku SKU, locationID LocationID, quantity int64) error {
+	key := getInventoryKey(sku, locationID)
+	cmd := rdb.Set(s.ctx, key, quantity, 0)
+	return cmd.Err()
+}
+
+var (
+	ErrInsufficientInventory = errors.New("insufficient inventory")
+	ErrInvalidQuantity       = errors.New("invalid quantity")
+	ErrMissingReservation    = errors.New("missing reservation")
+)
+
+func (s *RedisInventoryService) ReserveInventory(req ...ReserveRequest) error {
+	if len(req) == 0 {
+		return ErrMissingReservation
+	}
+
+	keys := make([]string, len(req))
+	args := make([]string, len(req))
+	for i, r := range req {
+		if r.Quantity <= 0 {
+			return ErrInvalidQuantity
+		}
+		keys[i] = getInventoryKey(r.SKU, r.LocationID)
+		args[i] = strconv.Itoa(int(r.Quantity))
+	}
+	cmd := reserveScript.Run(s.ctx, s.client, keys, args)
+	if err := cmd.Err(); err != nil {
+		return err
+	}
+	if val, err := cmd.Int(); err != nil {
+		return err
+	} else if val != 1 {
+		return ErrInsufficientInventory
+	}
+	return nil
+}
+
+var reserveScript = redis.NewScript(`
+-- Get the number of keys passed
+local num_keys = #KEYS
+
+-- Ensure the number of keys matches the number of quantities
+if num_keys ~= #ARGV then
+  return {err = "Script requires the same number of keys and quantities."}
+end
+
+local new_values = {}
+local payload = {}
+
+-- ---
+-- 1. CHECK PHASE
+-- ---
+-- Loop through all keys to check their values first
+for i = 1, num_keys do
+  local key = KEYS[i]
+  local quantity_to_check = tonumber(ARGV[i])
+
+  -- Fail if the quantity is not a valid number
+  if not quantity_to_check then
+    return {err = "Invalid quantity provided for key: " .. key}
+  end
+
+  -- Get the current value stored at the key
+  local current_val = tonumber(redis.call('GET', key))
+
+  -- Check the condition
+  -- Fail if:
+  -- 1. The key doesn't exist (current_val is nil)
+  -- 2. The value is not > the required quantity
+  if not current_val or current_val <= quantity_to_check then
+    -- Return 0 to indicate the operation failed and no changes were made
+    return 0
+  end
+
+  -- If the check passes, store the new value
+  local new_val = current_val - quantity_to_check
+  table.insert(new_values, new_val)
+
+  -- Add this key and its *new* value to our payload map
+  payload[key] = new_val
+end
+
+-- ---
+-- 2. UPDATE PHASE
+-- ---
+-- If the script reaches this point, all checks passed.
+-- Now, loop again and apply all the updates.
+for i = 1, num_keys do
+  local key = KEYS[i]
+  local new_val = new_values[i]
+
+  -- Set the key to its new calculated value
+  redis.call('SET', key, new_val)
+end
+local message_payload = cjson.encode(payload)
+
+-- Publish the JSON-encoded message to the specified channel
+redis.call('PUBLISH', "inventory_changed", message_payload)
+-- Return 1 to indicate the operation was successful
+return 1
+`)

pkg/inventory/types.go

@@ -0,0 +1,30 @@
+package inventory
+
+import "time"
+
+type SKU string
+
+type LocationID string
+
+type InventoryItem struct {
+	SKU        SKU
+	Quantity   int
+	LastUpdate time.Time
+}
+
+type Warehouse struct {
+	ID        LocationID
+	Name      string
+	Inventory []InventoryItem
+}
+
+type InventoryService interface {
+	GetInventory(sku SKU, locationID LocationID) (int64, error)
+	ReserveInventory(req ...ReserveRequest) error
+}
+
+type ReserveRequest struct {
+	SKU        SKU
+	LocationID LocationID
+	Quantity   uint32
+}