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From "stack (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-5926) Delete the master znode after a master crash
Date Thu, 17 May 2012 18:44:10 GMT

    [ https://issues.apache.org/jira/browse/HBASE-5926?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13278078#comment-13278078
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stack commented on HBASE-5926:
------------------------------

CleanZNode should be in the tool package or in zookeeper (probably the latter since thats
its dependencies)  ... hmmm.. but hangon, I see why you have it here... because its used by
master and regionserver packages.  Thats fine.  Its in the right place I'd say.

You should look at the javadoc that is created from your src.  Its going to be a jumble. 
Check it out.  You need a little bit of html in there at least for your list of strategy dependencies.

What is the filecontent?  We don't need any, right?  The name of the file is enough?

This should be boolean rather than int?  Or is it returned to shell?  If so, should say so
in the comment: "+   * @return if done returns 0 else -1."

Is CleanZNode a good name?  How about ZNodeCleaner or ZNodeClearer or CrashZNodeCleaner?

I think in HMasterCommandLine, should be start|stop|clear so it fits format of the other commands.

In MasterAddressTracker, can you get the znode sequence id and only delete if the sequence
id  matches?

                
> 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, 5926.v9.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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