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Date: Sat, 26 May 2012 17:41:23 +0000 (UTC)
From: "ramkrishna.s.vasudevan (JIRA)" <jira@apache.org>
To: issues@hbase.apache.org
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Subject: [jira] [Commented] (HBASE-6046) Master retry on ZK session expiry
 causes inconsistent region assignments.
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    [ https://issues.apache.org/jira/browse/HBASE-6046?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13284026#comment-13284026 ] 

ramkrishna.s.vasudevan commented on HBASE-6046:
-----------------------------------------------

When the master is retrying to come up in 
{code}
private boolean tryRecoveringExpiredZKSession() throws InterruptedException,
      IOException, KeeperException, ExecutionException {
{code}
We tend to just initialize the zk trackers, assign root and meta and finally assign any regions in transition.
But in this time if an RS has gone down we totally miss those callback and the logs are never splitted.  Also as the AM is reinitialized we always treat as a clean cluster start.
                
> Master retry on ZK session expiry causes inconsistent region assignments.
> -------------------------------------------------------------------------
>
>                 Key: HBASE-6046
>                 URL: https://issues.apache.org/jira/browse/HBASE-6046
>             Project: HBase
>          Issue Type: Bug
>          Components: master
>    Affects Versions: 0.92.1, 0.94.0
>            Reporter: Gopinathan A
>            Assignee: ramkrishna.s.vasudevan
>             Fix For: 0.92.2, 0.94.1
>
>
> 1> ZK Session timeout in the hmaster leads to bulk assignment though all the RSs are online.
> 2> While doing bulk assignment, if the master again goes down & restart(or backup comes up) all the node created in the ZK will now be tried to reassign to the new RSs. This is leading to double assignment.
> we had 2800 regions, among this 1900 region got double assignment, taking the region count to 4700. 

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