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https://issues.apache.org/jira/browse/HBASE-5099?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13176356#comment-13176356
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Jimmy Xiang commented on HBASE-5099:
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The timeout monitor thread in split log manager keeps logging this:
2011-12-27 00:00:06,759 DEBUG master.SplitLogManager
(SplitLogManager.java:chore(846)) - total tasks = 12 unassigned = 12
It shows no task assigned since no task znode was created yet.
Checked zookeeper, and the there was nothing under /hbase/splitlog
> 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
> Attachments: ZK-event-thread-waiting-for-root.png,
> distributed-log-splitting-hangs.png
>
>
> 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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