[jira] [Created] (SOLR-15106) Thread in OverseerTaskProcessor should not "return"

["Mathieu Marie (Jira)" <ji...@apache.org>]

Mathieu Marie created SOLR-15106:
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             Summary: Thread in OverseerTaskProcessor should not "return"
                 Key: SOLR-15106
                 URL: https://issues.apache.org/jira/browse/SOLR-15106
             Project: Solr
          Issue Type: Bug
      Security Level: Public (Default Security Level. Issues are Public)
          Components: SolrCloud
    Affects Versions: 8.6, master (9.0)
            Reporter: Mathieu Marie


I have encountered a scenario were ZK was not accessible for a long time (due to _jute.maxbuffer_ issue, but not related to the rest of this issue).
During that time, the ClusterStateUpdater and OC queues from the Overseer got filled with 1200+ messages.

Once we restored ZK availability, the ClusterStateUpdater queue got emptied, but not the OC one.

The Overseer stopped to dequeue from the OC queue.

After some digging in the code it seems that a *return* from the overseer thread starting the runners could be the issue.

Code in OverseerTaskProcessor.java (https://github.com/apache/lucene-solr/blob/master/solr/core/src/java/org/apache/solr/cloud/OverseerTaskProcessor.java#L357)
The lines of codes that immediately follow should also be reviewed carefully as they also return or interrupt the thread that is responsible to execute the runners.

Anyhow, if anybody hit that same issue, the quick workaround is to bump the overseer instance to elect a new overseer on another node.







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