Hello This is related to the Cache Management of HDFS As described in the documentation: https://hadoop.apache.org/docs/current/hadoop-project-dist/hadoop-hdfs/CentralizedCacheManagement.html In this architecture, the NameNode is responsible for coordinating all the DataNode off-heap caches in the cluster. The NameNode periodically receives a cache report from each DataNode which describes all the blocks cached on a given DN. The NameNode manages DataNode caches by piggybacking cache and uncache commands on the DataNode heartbeat. If the metric is going up, one possibility could be your namenode is too busy to handle the request
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