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Date: Mon, 23 Apr 2012 20:48:35 +0000 (UTC)
From: "stack (JIRA)" <jira@apache.org>
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Subject: [jira] [Commented] (HBASE-5849) On first cluster startup, RS aborts
 if root znode is not available
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    [ https://issues.apache.org/jira/browse/HBASE-5849?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13259937#comment-13259937 ] 

stack commented on HBASE-5849:
------------------------------

Patch lgtm.
                
> On first cluster startup, RS aborts if root znode is not available
> ------------------------------------------------------------------
>
>                 Key: HBASE-5849
>                 URL: https://issues.apache.org/jira/browse/HBASE-5849
>             Project: HBase
>          Issue Type: Bug
>          Components: master, regionserver, zookeeper
>    Affects Versions: 0.92.2, 0.96.0, 0.94.1
>            Reporter: Enis Soztutar
>            Assignee: Enis Soztutar
>         Attachments: HBASE-5849_v1.patch
>
>
> When launching a fresh new cluster, the master has to be started first, which might create race conditions for starting master and rs at the same time. 
> Master startup code is smt like this: 
>  - establish zk connection
>  - create root znodes in zk (/hbase)
>  - create ephemeral node for master /hbase/master, 
>  Region server start up code is smt like this: 
>  - establish zk connection
>  - check whether the root znode (/hbase) is there. If not, shutdown. 
>  - wait for the master to create znodes /hbase/master
> So, the problem is on the very first launch of the cluster, RS aborts to start since /hbase znode might not have been created yet (only the master creates it if needed). Since /hbase/ is not deleted on cluster shutdown, on subsequent cluster starts, it does not matter which order the servers are started. So this affects only first launchs. 

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