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Date: Fri, 30 Dec 2011 06:35:30 +0000 (UTC)
From: "Zhihong Yu (Updated) (JIRA)" <jira@apache.org>
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Subject: [jira] [Updated] (HBASE-5099) ZK event thread waiting for root
 region assignment may block server shutdown handler for the region sever
 the root region was on
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     [ https://issues.apache.org/jira/browse/HBASE-5099?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Zhihong Yu updated HBASE-5099:
------------------------------

    Summary: ZK event thread waiting for root region assignment may block server shutdown handler for the region sever the root region was on  (was: 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)
    
> ZK event thread waiting for root region assignment may block server shutdown handler for the region sever the root region was 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
>             Fix For: 0.92.0, 0.94.0
>
>         Attachments: 5099.92, 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-v5.patch, hbase-5099-v6.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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