Hello @SDL    This is an Old Thread & I assume your Team have moved on, yet wish to Update this Post for future references. It was observed that such Overnight Restart were resetting the default CleanUp (24 Hours) set via [1] in SolrConfig.XML of the respective Solr Collection (Sample from Ranger_Audits Collection). This caused the CleanUp to be postponed on a daily basis & causes Document PileUp beyond their Expiration. If Customer are restarting the Service nightly, It's advisable to set the CleanUp from 24 Hours to a Lower Value (Like, 20 or 22 Hours).    Regards, Smarak   [1]  <processor class="solr.processor.DocExpirationUpdateProcessorFactory"> <int name="autoDeletePeriodSeconds">86400</int> <str name="ttlFieldName">_ttl_</str> <str name="expirationFieldName">_expire_at_</str> </processor> ... View more

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       ... View more