docs: add changelog about redis cache

CHANGELOG.md

@@ -32,6 +32,7 @@ We use *breaking :warning:* to mark changes that are not backward compatible (re
 - [#4903](https://github.com/thanos-io/thanos/pull/4903) Compactor: Added tracing support for compaction.
 - [#4909](https://github.com/thanos-io/thanos/pull/4909) Compactor: Add flag --max-time / --min-time to filter blocks that are ready to be compacted.
 - [#4942](https://github.com/thanos-io/thanos/pull/4942) Tracing: add `traceid_128bit` support for jaeger.
+- [#4888](https://github.com/thanos-io/thanos/pull/4888) Cache: support redis cache backend.
 
 ### Fixed
 

pkg/cacheutil/redis_client.go

@@ -168,7 +168,7 @@ func NewRedisClientWithConfig(logger log.Logger, name string, config RedisClient
 	}
 	duration := promauto.With(reg).NewHistogramVec(prometheus.HistogramOpts{
 		Name:    "thanos_redis_operation_duration_seconds",
-		Help:    "Duration of operations against memcached.",
+		Help:    "Duration of operations against redis.",
 		Buckets: []float64{0.001, 0.005, 0.01, 0.025, 0.05, 0.1, 0.2, 0.5, 1, 3, 6, 10},
 	}, []string{"operation"})
 	c.durationSet = duration.WithLabelValues(opSet)

pkg/queryfrontend/cache.go

@@ -34,7 +34,6 @@ func (t thanosCacheKeyGenerator) GenerateCacheKey(userID string, r queryrange.Re
 		i := 0
 		for ; i < len(t.resolutions) && t.resolutions[i] > tr.MaxSourceResolution; i++ {
 		}
-		// Cache key should has a uniq prefix, We use `fe` represent frontend.
 		return fmt.Sprintf("fe:%s:%s:%d:%d:%d", userID, tr.Query, tr.Step, currentInterval, i)
 	case *ThanosLabelsRequest:
 		return fmt.Sprintf("fe:%s:%s:%s:%d", userID, tr.Label, tr.Matchers, currentInterval)

pkg/store/cache/caching_bucket_factory.go

@@ -101,7 +101,7 @@ func NewCachingBucketFromYaml(yamlContent []byte, bucket objstore.Bucket, logger
 	case string(RedisBucketCacheProvider):
 		redisCache, err := cacheutil.NewRedisClient(logger, "caching-bucket", backendConfig, reg)
 		if err != nil {
-			return nil, errors.Wrapf(err, "failed to create memcached client")
+			return nil, errors.Wrapf(err, "failed to create redis client")
 		}
 		c = cache.NewRedisCache("caching-bucket", logger, redisCache, reg)
 	default:

pkg/store/cache/memcached.go

@@ -53,7 +53,7 @@ func NewRemoteIndexCache(logger log.Logger, cacheClient cacheutil.RemoteCacheCli
 	c.hits.WithLabelValues(cacheTypePostings)
 	c.hits.WithLabelValues(cacheTypeSeries)
 
-	level.Info(logger).Log("msg", "created cacheClient index cache")
+	level.Info(logger).Log("msg", "created index cache")
 
 	return c, nil
 }