feat: Allow cache reading from replicas

README.md

@@ -444,7 +444,11 @@ make run
 - RedisCacheHost
   - string
   - default: "redis:6379"
-  - hostname and port for the Redis service
+  - hostname and port for the Redis write host (primary)
+- RedisCacheReadHosts
+  - []string
+  - default: []
+  - List of Redis replica hostnames (host:port) to use for read operations. Reads are distributed round-robin across replicas. Falls back to RedisCacheHost when empty.
 - RedisCachePassword
   - string
   - default: ""
@@ -640,7 +644,10 @@ http:
           forwardedHeadersCustomName: X-Custom-Header
           remediationHeadersCustomName: cs-remediation
           redisCacheEnabled: false
-          redisCacheHost: "redis:6379"
+          redisCacheHost: "redis-primary:6379"
+          redisCacheReadHosts:
+            - "redis-replica-1:6379"
+            - "redis-replica-2:6379"
           redisCachePassword: password
           redisCacheDatabase: "5"
           redisCacheUnreachableBlock: true

bouncer.go

@@ -268,6 +268,7 @@ func New(_ context.Context, next http.Handler, config *configuration.Config, nam
 		log,
 		config.RedisCacheEnabled,
 		config.RedisCacheHost,
+		config.RedisCacheReadHosts,
 		config.RedisCachePassword,
 		config.RedisCacheDatabase,
 	)

pkg/cache/cache.go

@@ -6,6 +6,7 @@ import (
 	"errors"
 	"fmt"
 	"log/slog"
+	"sync/atomic"
 
 	ttl_map "github.com/leprosus/golang-ttl-map"
 	simpleredis "github.com/maxlerebourg/simpleredis"
@@ -27,10 +28,7 @@ const (
 )
 
 //nolint:gochecknoglobals
-var (
-	redis simpleredis.SimpleRedis
-	cache = ttl_map.New()
-)
+var cache = ttl_map.New()
 
 type localCache struct{}
 
@@ -52,33 +50,53 @@ func (localCache) delete(key string) {
 }
 
 type redisCache struct {
-	log *slog.Logger
+	log     *slog.Logger
+	writer  simpleredis.SimpleRedis
+	readers []simpleredis.SimpleRedis
+	counter atomic.Uint64
 }
 
-func (redisCache) get(key string) (string, error) {
-	value, err := redis.Get(key)
-	valueString := string(value)
-	if err == nil && len(valueString) > 0 {
-		return valueString, nil
+func (rc *redisCache) nextReader() *simpleredis.SimpleRedis {
+	n := len(rc.readers)
+	if n == 0 {
+		return &rc.writer
 	}
-	errRedisMessage := err.Error()
-	if errRedisMessage == simpleredis.RedisMiss {
-		return "", errors.New(CacheMiss)
-	}
-	if errRedisMessage == simpleredis.RedisUnreachable {
-		return "", errors.New(CacheUnreachable)
-	}
-	return "", err
+	idx := rc.counter.Add(1) % uint64(n)
+	return &rc.readers[idx]
 }
 
-func (rc redisCache) set(key, value string, duration int64) {
-	if err := redis.Set(key, []byte(value), duration); err != nil {
+func redisResultToString(value []byte, err error) (string, error) {
+	if err == nil {
+		valueString := string(value)
+		if len(valueString) > 0 {
+			return valueString, nil
+		}
+	}
+	if err != nil {
+		switch err.Error() {
+		case simpleredis.RedisMiss:
+			return "", errors.New(CacheMiss)
+		case simpleredis.RedisUnreachable:
+			return "", errors.New(CacheUnreachable)
+		}
+		return "", err
+	}
+	return "", errors.New(CacheMiss)
+}
+
+func (rc *redisCache) get(key string) (string, error) {
+	value, err := rc.nextReader().Get(key)
+	return redisResultToString(value, err)
+}
+
+func (rc *redisCache) set(key, value string, duration int64) {
+	if err := rc.writer.Set(key, []byte(value), duration); err != nil {
 		rc.log.Error("cache:setDecisionRedisCache" + err.Error())
 	}
 }
 
-func (rc redisCache) delete(key string) {
-	if err := redis.Del(key); err != nil {
+func (rc *redisCache) delete(key string) {
+	if err := rc.writer.Del(key); err != nil {
 		rc.log.Error("cache:deleteDecisionRedisCache " + err.Error())
 	}
 }
@@ -96,15 +114,21 @@ type Client struct {
 }
 
 // New Initialize cache client.
-func (c *Client) New(log *slog.Logger, isRedis bool, host, pass, database string) {
+func (c *Client) New(log *slog.Logger, isRedis bool, writeHost string, readHosts []string, pass, database string) {
 	c.log = log
 	if isRedis {
-		redis.Init(host, pass, database)
-		c.cache = &redisCache{log: log}
+		rc := &redisCache{log: log}
+		rc.writer.Init(writeHost, pass, database)
+		for _, h := range readHosts {
+			var r simpleredis.SimpleRedis
+			r.Init(h, pass, database)
+			rc.readers = append(rc.readers, r)
+		}
+		c.cache = rc
 	} else {
 		c.cache = &localCache{}
 	}
-	c.log.Debug(fmt.Sprintf("cache:New initialized isRedis:%v", isRedis))
+	c.log.Debug(fmt.Sprintf("cache:New initialized isRedis:%v writeHost:%v readHosts:%v", isRedis, writeHost, readHosts))
 }
 
 // Delete delete decision in cache.

pkg/configuration/configuration.go

@@ -96,6 +96,7 @@ type Config struct {
 	ClientTrustedIPs                           []string `json:"clientTrustedIps,omitempty"`
 	RedisCacheEnabled                          bool     `json:"redisCacheEnabled,omitempty"`
 	RedisCacheHost                             string   `json:"redisCacheHost,omitempty"`
+	RedisCacheReadHosts                        []string `json:"redisCacheReadHosts,omitempty"`
 	RedisCachePassword                         string   `json:"redisCachePassword,omitempty"`
 	RedisCachePasswordFile                     string   `json:"redisCachePasswordFile,omitempty"`
 	RedisCacheDatabase                         string   `json:"redisCacheDatabase,omitempty"`
@@ -172,6 +173,7 @@ func New() *Config {
 		ClientTrustedIPs:                  []string{},
 		RedisCacheEnabled:                 false,
 		RedisCacheHost:                    "redis:6379",
+		RedisCacheReadHosts:               []string{},
 		RedisCachePassword:                "",
 		RedisCacheDatabase:                "",
 		RedisCacheUnreachableBlock:        true,