✨ feat(cache): Add Redis embedding cache support. Closes #5

- Add Redis-based caching layer to avoid redundant Gemini API calls.
- Improves performance and reduces API usage, especially useful during development.

Author: nmdra

cmd/main.go

@@ -23,7 +23,8 @@ type config struct {
 	port   int
 	apiKey string
 	db     struct {
-		dsn string
+		dsn   string
+		redis string
 	}
 }
 
@@ -32,10 +33,12 @@ func loadConfig() config {
 
 	defaultAPIKey := os.Getenv("GEMINI_API_KEY")
 	defaultDSN := os.Getenv("DATABASE_URL")
+	defaultRedisUrl := os.Getenv("REDIS_URL")
 
 	flag.IntVar(&cfg.port, "port", 8080, "API server port")
 	flag.StringVar(&cfg.apiKey, "apikey", defaultAPIKey, "Gemini API Key")
 	flag.StringVar(&cfg.db.dsn, "db-dsn", defaultDSN, "PostgreSQL DSN")
+	flag.StringVar(&cfg.db.redis, "redis", defaultRedisUrl, "Redis instance URL")
 	flag.Parse()
 
 	return cfg
@@ -64,13 +67,26 @@ func main() {
 	defer dbpool.Close()
 	logger.Info("Connected to PostgreSQL")
 
+	var embedder embed.Embedder
+
 	// Embedding client
-	embedder, err := embed.NewGeminiEmbedder(ctx, logger, cfg.apiKey)
+	baseEmbedder, err := embed.NewGeminiEmbedder(ctx, logger, cfg.apiKey)
 	if err != nil {
 		logger.Error("Failed to initialize embedder", "error", err)
 		os.Exit(1)
 	}
 
+	if cfg.db.redis != "" {
+		redisClient := db.NewRedisClient(cfg.db.redis, logger)
+		embedder = &embed.CachedEmbedder{
+			Base:   baseEmbedder,
+			Redis:  redisClient,
+			Logger: logger,
+		}
+	} else {
+		embedder = baseEmbedder
+	}
+
 	// Services and handlers
 	repo := repository.New(dbpool)
 	bookService := &service.BookService{
@@ -87,7 +103,7 @@ func main() {
 	e.Use(middleware.Logger())
 	e.Use(middleware.Recover())
 	e.Use(middleware.TimeoutWithConfig(middleware.TimeoutConfig{
-		Timeout: 5 * time.Second,
+		Timeout:      5 * time.Second,
 		ErrorMessage: "Request timed out.",
 		OnTimeoutRouteErrorHandler: func(err error, c echo.Context) {
 			logger.Warn("Timeout on route", "path", c.Path(), "error", err)

docker-compose.yml

@@ -11,5 +11,15 @@ services:
     volumes:
       - pgdata:/var/lib/postgresql/data
 
+  redis:
+    image: redis:alpine
+    container_name: redis-cache
+    ports:
+      - "6379:6379"
+    command: redis-server --save 20 1 --loglevel warning
+    volumes:
+      - redis_data:/data
+    
 volumes:
-  pgdata:
+  pgdata:
+  redis_data:

go.mod

@@ -3,11 +3,13 @@ module semantic-search
 go 1.24.5
 
 require (
+	github.com/cespare/xxhash/v2 v2.3.0
 	github.com/jackc/pgx/v5 v5.7.5
 	github.com/joho/godotenv v1.5.1
 	github.com/labstack/echo/v4 v4.13.4
 	github.com/lmittmann/tint v1.1.2
 	github.com/pgvector/pgvector-go v0.3.0
+	github.com/redis/go-redis/v9 v9.11.0
 	github.com/stretchr/testify v1.10.0
 	google.golang.org/genai v1.15.0
 )
@@ -17,6 +19,7 @@ require (
 	cloud.google.com/go/auth v0.9.3 // indirect
 	cloud.google.com/go/compute/metadata v0.5.0 // indirect
 	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/dgryski/go-rendezvous v0.0.0-20200823014737-9f7001d12a5f // indirect
 	github.com/golang/groupcache v0.0.0-20210331224755-41bb18bfe9da // indirect
 	github.com/google/go-cmp v0.7.0 // indirect
 	github.com/google/s2a-go v0.1.8 // indirect

go.sum

@@ -8,13 +8,21 @@ cloud.google.com/go/compute/metadata v0.5.0/go.mod h1:aHnloV2TPI38yx4s9+wAZhHykW
 entgo.io/ent v0.14.3 h1:wokAV/kIlH9TeklJWGGS7AYJdVckr0DloWjIcO9iIIQ=
 entgo.io/ent v0.14.3/go.mod h1:aDPE/OziPEu8+OWbzy4UlvWmD2/kbRuWfK2A40hcxJM=
 github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03qcyfWMU=
+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/census-instrumentation/opencensus-proto v0.2.1/go.mod h1:f6KPmirojxKA12rnyqOA5BBL4O983OfeGPqjHWSTneU=
+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/client9/misspell v0.3.4/go.mod h1:qj6jICC3Q7zFZvVWo7KLAzC3yx5G7kyvSDkc90ppPyw=
 github.com/cncf/udpa/go v0.0.0-20191209042840-269d4d468f6f/go.mod h1:M8M6+tZqaGXZJjfX53e64911xZQV5JYwmTeXPW+k8Sc=
 github.com/creack/pty v1.1.9/go.mod h1:oKZEueFk5CKHvIhNR5MUki03XCEU+Q6VDXinZuGJ33E=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/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/envoyproxy/go-control-plane v0.9.0/go.mod h1:YTl/9mNaCwkRvm6d1a2C3ymFceY/DCBVvsKhRF0iEA4=
 github.com/envoyproxy/go-control-plane v0.9.1-0.20191026205805-5f8ba28d4473/go.mod h1:YTl/9mNaCwkRvm6d1a2C3ymFceY/DCBVvsKhRF0iEA4=
 github.com/envoyproxy/go-control-plane v0.9.4/go.mod h1:6rpuAdCZL397s3pYoYcLgu1mIlRU8Am5FuJP05cCM98=
@@ -91,6 +99,8 @@ github.com/pgvector/pgvector-go v0.3.0/go.mod h1:duFy+PXWfW7QQd5ibqutBO4GxLsUZ9R
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/prometheus/client_model v0.0.0-20190812154241-14fe0d1b01d4/go.mod h1:xMI15A0UPsDsEKsMN9yxemIoYk6Tm2C1GtYGdfGttqA=
+github.com/redis/go-redis/v9 v9.11.0 h1:E3S08Gl/nJNn5vkxd2i78wZxWAPNZgUNTp8WIJUAiIs=
+github.com/redis/go-redis/v9 v9.11.0/go.mod h1:huWgSWd8mW6+m0VPhJjSSQ+d6Nh1VICQ6Q5lHuCH/Iw=
 github.com/rogpeppe/go-internal v1.9.0 h1:73kH8U+JUqXU8lRuOHeVHaa/SZPifC7BkcraZVejAe8=
 github.com/rogpeppe/go-internal v1.9.0/go.mod h1:WtVeX8xhTBvf0smdhujwtBcq4Qrzq/fJaraNFVN+nFs=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=

internal/db/db.go

@@ -18,21 +18,18 @@ func NewPool(ctx context.Context, dsn string, logger *slog.Logger) (*pgxpool.Poo
 	ctx, cancel := context.WithTimeout(ctx, 5*time.Second)
 	defer cancel()
 
-	logger.Info("Parsing database configuration")
 	config, err := pgxpool.ParseConfig(dsn)
 	if err != nil {
 		logger.Error("Failed to parse DSN", "error", err)
 		return nil, fmt.Errorf("failed to parse DSN: %w", err)
 	}
 
-	logger.Info("Creating database connection pool")
 	pool, err := pgxpool.NewWithConfig(ctx, config)
 	if err != nil {
 		logger.Error("Failed to create DB pool", "error", err)
 		return nil, fmt.Errorf("failed to create pool: %w", err)
 	}
 
-	logger.Info("Pinging database to verify connection")
 	if err := pool.Ping(ctx); err != nil {
 		pool.Close()
 		return nil, fmt.Errorf("failed to ping database: %w", err)

internal/db/redis.go

@@ -0,0 +1,30 @@
+package db
+
+import (
+	"context"
+	"log/slog"
+	"time"
+
+	"github.com/redis/go-redis/v9"
+)
+
+// NewRedisClient creates a Redis client and logs the connection status.
+func NewRedisClient(addr string, logger *slog.Logger) *redis.Client {
+	client := redis.NewClient(&redis.Options{
+		Addr:         addr,
+		ReadTimeout:  1 * time.Second,
+		WriteTimeout: 1 * time.Second,
+		PoolSize:     10,
+	})
+
+	ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
+	defer cancel()
+
+	if err := client.Ping(ctx).Err(); err != nil {
+		logger.Error("Failed to connect to Redis", "addr", addr, "error", err)
+		panic("Failed to connect to Redis: " + err.Error())
+	}
+
+	logger.Info("Connected to Redis", "addr", addr)
+	return client
+}

internal/embed/cached_embedder.go

@@ -0,0 +1,58 @@
+package embed
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"log/slog"
+	"strings"
+	"time"
+
+	"github.com/cespare/xxhash/v2"
+	"github.com/redis/go-redis/v9"
+)
+
+type CachedEmbedder struct {
+	Base   Embedder
+	Redis  *redis.Client
+	Logger *slog.Logger
+}
+
+func (c *CachedEmbedder) Embed(ctx context.Context, input string) ([]float32, error) {
+	normalized := strings.TrimSpace(strings.ToLower(input))
+	hash := xxhash.Sum64String(normalized)
+	cacheKey := fmt.Sprintf("embed:%x", hash)
+
+	cached, err := c.Redis.Get(ctx, cacheKey).Bytes()
+	if err == nil {
+		var vec []float32
+		if err := json.Unmarshal(cached, &vec); err == nil {
+			c.Logger.Info("Embedding cache hit", "query", input)
+			return vec, nil
+		}
+		c.Logger.Warn("Failed to unmarshal cached embedding", "error", err)
+	} else if err != redis.Nil {
+		// Only log real Redis errors (not cache misses)
+		c.Logger.Warn("Redis GET failed", "key", cacheKey, "error", err)
+	}
+
+	// Cache Miss
+	vec, err := c.Base.Embed(ctx, input)
+	if err != nil {
+		return nil, fmt.Errorf("embedding failed: %w", err)
+	}
+
+	data, err := json.Marshal(vec)
+	if err != nil {
+		c.Logger.Warn("Failed to marshal embedding for cache", "error", err)
+	} else {
+		err := c.Redis.Set(ctx, cacheKey, data, 24*time.Hour).Err()
+		if err != nil {
+			c.Logger.Warn("Failed to store embedding in Redis", "key", cacheKey, "error", err)
+		} else {
+			c.Logger.Debug("Cached embedding", "query", input)
+		}
+	}
+
+	return vec, nil
+}

internal/embed/embed.go

@@ -19,9 +19,8 @@ type GeminiEmbedder struct {
 	logger *slog.Logger
 }
 
-func NewGeminiEmbedder(ctx context.Context, logger *slog.Logger, apikey string) (*GeminiEmbedder, error) {
+func NewGeminiEmbedder(ctx context.Context, logger *slog.Logger, apiKey string) (*GeminiEmbedder, error) {
 
-	apiKey := apikey
 	if apiKey == "" {
 		return nil, errors.New("GEMINI_API_KEY is not set")
 	}