DOCS-13389 feature flag to turn on/off catalog cache refresh for a targeted shard

Author: kanchana-mongodb

source/reference/parameters.txt

@@ -2534,6 +2534,36 @@ Sharding Parameters
       - :serverstatus:`shardedIndexConsistency` metrics returned by the
         :dbcommand:`serverStatus` commandq
 
+.. parameter:: enableFinerGrainedCatalogCacheRefresh
+
+   .. versionadded:: 4.4
+
+   *Type*: boolean
+
+   *Default*: true
+
+   |both|
+
+   This parameter allows the catalog cache to be refreshed only if the 
+   shard needs to be refreshed. If disabled, any stale chunk will cause 
+   the entire chunk distribution for a collection to be considered stale 
+   and force all :ref:`routers <sharded-cluster-query-routing>` who 
+   contact the shard to refresh their shard catalog cache.
+
+   You can only set this parameter during start-up and cannot change
+   this setting using the :dbcommand:`setParameter` database command.
+
+   .. code-block:: sh
+
+      mongod --setParameter enableFinerGrainedCatalogCacheRefresh=true
+      mongos --setParameter enableFinerGrainedCatalogCacheRefresh=true
+      
+   .. seealso:: 
+
+      - :ref:`sharding-background`
+
+      - :serverstatus:`shardingStatistics.catalogCache`
+
 .. parameter:: maxTimeMSForHedgedReads
 
    .. versionadded:: 4.4

source/release-notes/4.4.txt

@@ -739,6 +739,23 @@ Jumbo Chunk Migration
 
    .. include:: /includes/extracts/4.4-changes-migrate-jumbo-chunks.rst
 
+Improved Catalog Cache Refresh 
+``````````````````````````````
+
+Starting in 4.4, if there is a stale chunk, the catalog cache is only 
+refreshed when :ref:`routers <sharded-cluster-query-routing>` access 
+a shard that previously had or currently has that chunk. 
+
+Prior to MongoDB 4.4, any stale chunk caused the entire chunk distribution 
+for a collection to be marked as stale and forced all 
+:ref:`routers <sharded-cluster-query-routing>` who contact the shard 
+to refresh their shard catalog cache. MongoDB 4.4 adds the 
+:parameter:`enableFinerGrainedCatalogCacheRefresh` startup parameter 
+for disabling catalog cache refresh for only a targeted shard and using 
+the older catalog cache refresh behavior. The 
+:parameter:`enableFinerGrainedCatalogCacheRefresh` parameter defaults to 
+``true``.
+
 Automatically Split ``system.sessions`` Collection
 ``````````````````````````````````````````````````