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From "nkeywal (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-5926) Delete the master znode after a master crash
Date Thu, 17 May 2012 17:24:11 GMT

    [ https://issues.apache.org/jira/browse/HBASE-5926?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13277996#comment-13277996
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nkeywal commented on HBASE-5926:
--------------------------------

bq. javadoc
done.

bq. readMyEphemeralNodeOnDisk() throws IOException but writeMyEphemeralNodeOnDisk() doesn't.
What was the reason ?
When we write we ignore the results (i.e. we don't stop the master or the region server if
we can't store the znode, we just continue). When we read, we're interested in the exception:
the pattern in HMasterCommandLine is to return -1 on error.

bq. Please add ' contents' at the end of the above.
ok.

bq. Should the setting be restored before exiting the above method ?
I now clone the conf.

                
> Delete the master znode after a master crash
> --------------------------------------------
>
>                 Key: HBASE-5926
>                 URL: https://issues.apache.org/jira/browse/HBASE-5926
>             Project: HBase
>          Issue Type: Improvement
>          Components: master, scripts
>    Affects Versions: 0.96.0
>            Reporter: nkeywal
>            Assignee: nkeywal
>            Priority: Minor
>             Fix For: 0.96.0
>
>         Attachments: 5926.v6.patch, 5926.v8.patch
>
>
> This is the continuation of the work done in HBASE-5844.
> But we can't apply exactly the same strategy: for the region server, there is a znode
per region server, while for the master & backup master there is a single znode for both.
> So if we apply the same strategy as for a regionserver, we may have this scenario:
> 1) Master starts
> 2) Backup master starts
> 3) Master dies
> 4) ZK detects it
> 5) Backup master receives the update from ZK
> 6) Backup master creates the new master node and become the main master
> 7) Previous master script continues
> 8) Previous master script deletes the master node in ZK
> 9) => issue: we deleted the node just created by the new master
> This should not happen often (usually the znode will be deleted soon enough), but it
can happen.

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