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Date: Mon, 23 Apr 2012 20:42:33 +0000 (UTC)
From: "Enis Soztutar (JIRA)" <jira@apache.org>
To: issues@hbase.apache.org
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Subject: [jira] [Updated] (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:all-tabpanel ]

Enis Soztutar updated HBASE-5849:
---------------------------------

    Attachment: HBASE-5849_v1.patch

Attaching a simple patch. Applies to trunk, 0.92 and 0.94 branches. 

Tested this with pseudo-distributed setup on my laptop, by first launching regionserver, and observing that it does actually wait for the master to boot up, instead of aborting. I'll try to come up with a boot order unit test shortly.
                
> 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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