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https://issues.apache.org/jira/browse/HBASE-5099?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Jimmy Xiang updated HBASE-5099:
-------------------------------

    Attachment: hbase-5099-v4.patch
    
> ZK event thread waiting for root region while server shutdown handler waiting 
> for event thread to finish distributed log splitting to recover the region 
> sever the root region is on
> ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: HBASE-5099
>                 URL: https://issues.apache.org/jira/browse/HBASE-5099
>             Project: HBase
>          Issue Type: Bug
>    Affects Versions: 0.92.0, 0.94.0
>            Reporter: Jimmy Xiang
>            Assignee: Jimmy Xiang
>         Attachments: ZK-event-thread-waiting-for-root.png, 
> distributed-log-splitting-hangs.png, hbase-5099-v2.patch, 
> hbase-5099-v3.patch, hbase-5099-v4.patch, hbase-5099.patch
>
>
> A RS died.  The ServerShutdownHandler kicked in and started the logspliting.  
> SpliLogManager
> installed the tasks asynchronously, then started to wait for them to complete.
> The task znodes were not created actually.  The requests were just queued.
> At this time, the zookeeper connection expired.  HMaster tried to recover the 
> expired ZK session.
> During the recovery, a new zookeeper connection was created.  However, this 
> master became the
> new master again.  It tried to assign root and meta.
> Because the dead RS got the old root region, the master needs to wait for the 
> log splitting to complete.
> This waiting holds the zookeeper event thread.  So the async create split 
> task is never retried since
> there is only one event thread, which is waiting for the root region assigned.

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