[jira] [Updated] (HBASE-8539) Double(or tripple ...) ZooKeeper listeners of the same type when Master recovers from ZK SessionExpiredException

["Jeffrey Zhong (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HBASE-8539?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Jeffrey Zhong updated HBASE-8539:
---------------------------------

    Attachment: double-registered listeners.png
    
> Double(or tripple ...) ZooKeeper listeners of the same type when Master recovers from ZK SessionExpiredException
> ----------------------------------------------------------------------------------------------------------------
>
>                 Key: HBASE-8539
>                 URL: https://issues.apache.org/jira/browse/HBASE-8539
>             Project: HBase
>          Issue Type: Bug
>          Components: master
>    Affects Versions: 0.98.0, 0.94.7, 0.95.0
>            Reporter: Jeffrey Zhong
>            Assignee: Jeffrey Zhong
>         Attachments: double-registered listeners.png
>
>
> When Master tries to recover from zookeeper session expired exceptions, we don't clean old registered listener instances. Therefore, it may end up we have two(or more) listeners to double handling same events. Attached a screen shot from debugger to show the issue.
> I considered to limit one listener per class while I think that would limit the listener usage so I choose to clear exiting listeners during recovery for the fix.
> (This issue is unrelated to the issue HBASE-8365 because I verified there is no dup-listeners when HBASE-8365 happened)

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