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Date: Sat, 7 Jul 2012 21:32:36 +0000 (UTC)
From: "Himanshu Vashishtha (JIRA)" <jira@apache.org>
To: issues@hbase.apache.org
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Subject: [jira] [Commented] (HBASE-5549) Master can fail if ZooKeeper
 session expires
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    [ https://issues.apache.org/jira/browse/HBASE-5549?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13408782#comment-13408782 ] 

Himanshu Vashishtha commented on HBASE-5549:
--------------------------------------------

Thanks for looking into this. 
Since the update is happening inside an inner class, it should be final (volatile is not possible). I will wait/notify on isClosed array object, and upload the patch in a new jira.
                
> Master can fail if ZooKeeper session expires
> --------------------------------------------
>
>                 Key: HBASE-5549
>                 URL: https://issues.apache.org/jira/browse/HBASE-5549
>             Project: HBase
>          Issue Type: Bug
>          Components: master, zookeeper
>    Affects Versions: 0.96.0
>         Environment: all
>            Reporter: nkeywal
>            Assignee: nkeywal
>            Priority: Minor
>             Fix For: 0.96.0
>
>         Attachments: 5549.v10.patch, 5549.v11.patch, 5549.v6.patch, 5549.v7.patch, 5549.v8.patch, 5549.v9.patch, nochange.patch
>
>
> There is a retry mechanism in RecoverableZooKeeper, but when the session expires, the whole ZooKeeperWatcher is recreated, hence the retry mechanism does not work in this case. This is why a sleep is needed in TestZooKeeper#testMasterSessionExpired: we need to wait for ZooKeeperWatcher to be recreated before using the connection.
> This can happen in real life, it can happen when:
> - master & zookeeper starts
> - zookeeper connection is cut
> - master enters the retry loop
> - in the meantime the session expires
> - the network comes back, the session is recreated
> - the retries continues, but on the wrong object, hence fails.

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