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From "Clara Xiong (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HBASE-15251) During a cluster restart, Hmaster thinks it is a failover by mistake
Date Thu, 11 Feb 2016 01:09:18 GMT
Clara Xiong created HBASE-15251:

             Summary: During a cluster restart, Hmaster thinks it is a failover by mistake
                 Key: HBASE-15251
                 URL: https://issues.apache.org/jira/browse/HBASE-15251
             Project: HBase
          Issue Type: Bug
          Components: master
    Affects Versions: 0.98.15, 2.0.0
            Reporter: Clara Xiong
            Assignee: Clara Xiong

We often need to do cluster restart as part of release for a cluster of > 1000 nodes. We
have tried our best to get clean shutdown but 50% of the time, hmaster still thinks it is
a failover. This increases the restart time from 5 min to 30 min and decreases locality from
95% to 5% since we didn't use a balancer. We had a bug HBASE-14129 but the fix didn't work.

After adding more logging and inspecting the logs, we identified two things that trigger the
failover handling:
1.  When Hmaster.AssignmentManager detects any dead servers on service manager during joinCluster(),
it determines this is a failover without further check. I added a check whether there is even
any region assigned to these servers. During a clean restart, the regions are not even assigned.
2. When there are some leftover empty folders for log and split directories or empty wal files,
it is already treated as a failover. I added a check for that. Although this can be resolved
by manual clean up, it is still too tedious for restarting a large cluster.

Patch will follow shortly.

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