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Date: Tue, 14 Mar 2017 14:48:41 +0000 (UTC)
From: "Lars George (JIRA)" <jira@apache.org>
To: issues@hbase.apache.org
Message-ID: <JIRA.12938402.1455152922000.15287.1489502921629@Atlassian.JIRA>
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Subject: [jira] [Commented] (HBASE-15251) During a cluster restart, Hmaster
 thinks it is a failover by mistake
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archived-at: Tue, 14 Mar 2017 14:48:48 -0000


    [ https://issues.apache.org/jira/browse/HBASE-15251?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15924349#comment-15924349 ] 

Lars George commented on HBASE-15251:
-------------------------------------

I believe this is not enough, as a failed server should be handled better, no matter if it had regions or not. Also, this should be ported to all 1.x branches.

> 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: 2.0.0
>            Reporter: Clara Xiong
>            Assignee: Clara Xiong
>             Fix For: 2.0.0
>
>         Attachments: HBASE-15251-master.patch, HBASE-15251-master-v1.patch
>
>
> 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 99% to 5% since we didn't use a locality-aware 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 also treated as a failover. I added a check for that. Although this can be resolved by manual cleanup, it is still too tedious for restarting a large cluster.
> Patch will follow shortly. The fix is tested and used in production now.


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