Add index cache max async concurrency (#6265)

Author: SungJin1212

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ## master / unreleased
 
+* [CHANGE] Change default value of `-blocks-storage.bucket-store.index-cache.memcached.max-async-concurrency` from `50` to `3` #6265
 * [CHANGE] Enable Compactor and Alertmanager in target all. #6204
 * [FEATURE] Query Frontend/Querier: Add protobuf codec `-api.querier-default-codec` and the option to choose response compression type `-querier.response-compression`. #5527
 * [FEATURE] Ruler: Experimental: Add `ruler.frontend-address` to allow query to query frontends instead of ingesters. #6151

docs/blocks-storage/querier.md

@@ -794,7 +794,7 @@ blocks_storage:
         # The maximum number of concurrent asynchronous operations can occur
         # when backfilling cache items.
         # CLI flag: -blocks-storage.bucket-store.index-cache.multilevel.max-async-concurrency
-        [max_async_concurrency: <int> | default = 50]
+        [max_async_concurrency: <int> | default = 3]
 
         # The maximum number of enqueued asynchronous operations allowed when
         # backfilling cache items.

docs/blocks-storage/store-gateway.md

@@ -891,7 +891,7 @@ blocks_storage:
         # The maximum number of concurrent asynchronous operations can occur
         # when backfilling cache items.
         # CLI flag: -blocks-storage.bucket-store.index-cache.multilevel.max-async-concurrency
-        [max_async_concurrency: <int> | default = 50]
+        [max_async_concurrency: <int> | default = 3]
 
         # The maximum number of enqueued asynchronous operations allowed when
         # backfilling cache items.

docs/configuration/config-file-reference.md

@@ -1327,7 +1327,7 @@ bucket_store:
       # The maximum number of concurrent asynchronous operations can occur when
       # backfilling cache items.
       # CLI flag: -blocks-storage.bucket-store.index-cache.multilevel.max-async-concurrency
-      [max_async_concurrency: <int> | default = 50]
+      [max_async_concurrency: <int> | default = 3]
 
       # The maximum number of enqueued asynchronous operations allowed when
       # backfilling cache items.

pkg/storage/tsdb/index_cache.go

@@ -132,7 +132,7 @@ func (cfg *MultiLevelIndexCacheConfig) Validate() error {
 }
 
 func (cfg *MultiLevelIndexCacheConfig) RegisterFlagsWithPrefix(f *flag.FlagSet, prefix string) {
-	f.IntVar(&cfg.MaxAsyncConcurrency, prefix+"max-async-concurrency", 50, "The maximum number of concurrent asynchronous operations can occur when backfilling cache items.")
+	f.IntVar(&cfg.MaxAsyncConcurrency, prefix+"max-async-concurrency", 3, "The maximum number of concurrent asynchronous operations can occur when backfilling cache items.")
 	f.IntVar(&cfg.MaxAsyncBufferSize, prefix+"max-async-buffer-size", 10000, "The maximum number of enqueued asynchronous operations allowed when backfilling cache items.")
 	f.IntVar(&cfg.MaxBackfillItems, prefix+"max-backfill-items", 10000, "The maximum number of items to backfill per asynchronous operation.")
 }