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From "Enis Soztutar (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-5849) On first cluster startup, RS aborts if root znode is not available
Date Mon, 23 Apr 2012 20:34:33 GMT

    [ https://issues.apache.org/jira/browse/HBASE-5849?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13259927#comment-13259927
] 

Enis Soztutar commented on HBASE-5849:
--------------------------------------

Upon inspecting further, it seems the patch for HBASE-4138 added the check for the base server
at region server start code. While it makes sense to check for znode.parent from the client
side, we should not do that for the regionserver. 
                
> 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
>
> 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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