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From "Bikas Saha (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (YARN-1307) Rethink znode structure for RM HA
Date Thu, 17 Oct 2013 17:21:43 GMT

    [ https://issues.apache.org/jira/browse/YARN-1307?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13798120#comment-13798120

Bikas Saha commented on YARN-1307:

I dont see much value in creating extra hierarchy for attempt Id's. We need a version info
field at the top for upgrades. We should avoid encoding sequence numbers in the znode names
since listing of paths is less protected in znode and the info may be visible to those who
dont have other access. Name encoding was used for HDFS since over-write operation is expensive.
In ZK, over-write is easy and so the data can be stored in the znode instead of its name wherever

 |     |----- (#ApplicationId1)
 |     |                 |----- (#ApplicationAttemptIds)
 |     |                 
 |     |----- (#ApplicationId2)
 |                      |----- (#ApplicationAttemptIds)
 |      ,,,,
       |----- RMDTSequenceNumber
       |----- RMDelegationToken

> Rethink znode structure for RM HA
> ---------------------------------
>                 Key: YARN-1307
>                 URL: https://issues.apache.org/jira/browse/YARN-1307
>             Project: Hadoop YARN
>          Issue Type: Sub-task
>          Components: resourcemanager
>            Reporter: Tsuyoshi OZAWA
>            Assignee: Tsuyoshi OZAWA
> Rethink for znode structure for RM HA is proposed in some JIRAs(YARN-659, YARN-1222).
The motivation of this JIRA is quoted from Bikas' comment in YARN-1222:
> {quote}
> We should move to creating a node hierarchy for apps such that all znodes for an app
are stored under an app znode instead of the app root znode. This will help in removeApplication
and also in scaling better on ZK. The earlier code was written this way to ensure create/delete
happens under a root znode for fencing. But given that we have moved to multi-operations globally,
this isnt required anymore.
> {quote}

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