thanos-io/thanos · error

failed to create inmemory cache

Error message

failed to create inmemory cache

What it means

When the cache type is IN-MEMORY, the factory builds an in-process cache via cache.NewInMemoryCache; any construction error is wrapped as 'failed to create inmemory cache'. The in-memory cache constructor validates its own config (max sizes, item limits).

Solutions

1. Check that max_size and max_size_items are non-negative and correctly formatted (e.g. 536870912 or 512MB)
2. Remove backend-specific keys that do not belong to the IN-MEMORY provider
3. Read the wrapped inner error for the exact invalid field
4. Validate config against the docs at Thanos caching_bucket.md for your version
5. Default the values (omit them) to let the library apply defaults

Example fix

// before
config:
  caches:
    chunks:
      max_size: -1
// after
config:
  caches:
    chunks:
      max_size: 512MB
      max_size_items: 0

if maxSize < 0 || maxSizeItems < 0 { return errors.New("in-memory cache sizes must be non-negative") }

cb, err := storecache.NewCachingBucketFromYaml(yamlContent, logger, reg, bucket, router)
if err != nil {
    if strings.Contains(err.Error(), "failed to create inmemory cache") {
        return fmt.Errorf("in-memory cache config invalid (check max_size/max_size_items): %w", err)
    }
    return err
}

When it happens

Trigger: CachingWithBackendConfig.Type == IN-MEMORY and NewInMemoryCache returns an error, typically due to invalid InMemoryCacheConfig values such as negative max_size or max_size_items, or an unmarshal failure of the backendConfig into the in-memory config.

Common situations: Setting max_size to a negative or unparseable size in the caching YAML, putting memcached-specific keys under an IN-MEMORY cache entry, or running a Thanos version where in-memory cache config options changed.

Understand the failure class

Background: "Invalid value" and "allowed values are" config errors: what your library rejected and how to fix it — this error's family across 41 libraries.

Related errors

• failed to parse template
• failed to execute template
• error while parsing config for request logging
• getting http client config
• parsing http config YAML

AI-assisted analysis of thanos-io/thanos@35b8b99117 (2026-09-07). Data as JSON: /api/errors/bbb218645cd49d32. Report an issue: GitHub.

Appendix: source

Thrown at pkg/store/cache/caching_bucket_factory.go:121

	cfg.CacheGetRange("chunks", nil, isTSDBChunkFile, config.ChunkSubrangeSize, config.ChunkObjectAttrsTTL, config.ChunkSubrangeTTL, config.MaxChunksGetRangeRequests)
	cfg.CacheExists("meta.jsons", nil, isMetaFile, config.MetafileExistsTTL, config.MetafileDoesntExistTTL)
	cfg.CacheGet("meta.jsons", nil, isMetaFile, int(config.MetafileMaxSize), config.MetafileContentTTL, config.MetafileExistsTTL, config.MetafileDoesntExistTTL)

	// Cache Iter requests for root.
	cfg.CacheIter("blocks-iter", nil, isBlocksRootDir, config.BlocksIterTTL, JSONIterCodec{}, cfgHash)

	switch strings.ToUpper(string(config.Type)) {
	case string(MemcachedBucketCacheProvider):
		var memcached cacheutil.RemoteCacheClient
		memcached, err := cacheutil.NewMemcachedClient(logger, "caching-bucket", backendConfig, reg)
		if err != nil {
			return nil, errors.Wrapf(err, "failed to create memcached client")
		}
		c = cache.NewMemcachedCache("caching-bucket", logger, memcached, reg)
	case string(InMemoryBucketCacheProvider):
		c, err = cache.NewInMemoryCache("caching-bucket", logger, reg, backendConfig)
		if err != nil {
			return nil, errors.Wrapf(err, "failed to create inmemory cache")
		}
	case string(GroupcacheBucketCacheProvider):
		const basePath = "/_galaxycache/"

		c, err = cache.NewGroupcache(logger, reg, backendConfig, basePath, r, bucket, cfg)
		if err != nil {
			return nil, errors.Wrap(err, "failed to create groupcache")
		}

	case string(RedisBucketCacheProvider):
		redisCache, err := cacheutil.NewRedisClient(logger, "caching-bucket", backendConfig, reg)
		if err != nil {
			return nil, errors.Wrapf(err, "failed to create redis client")
		}
		c = cache.NewRedisCache("caching-bucket", logger, redisCache, reg)
	default:
		return nil, errors.Errorf("unsupported cache type: %s", config.Type)
	}

View on GitHub (pinned to 35b8b99117)