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From "Bikas Saha (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (YARN-1307) Rethink znode structure for RM HA
Date Tue, 22 Oct 2013 16:40:42 GMT

    [ https://issues.apache.org/jira/browse/YARN-1307?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13801995#comment-13801995
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Bikas Saha commented on YARN-1307:
----------------------------------

To be clear, each app, app attempt, delegation token, secret key are stored separately in
their own znodes. We are not batching multiple of them in the same znode. Are you suggesting
that we batch them in a znode? e.g. all delegation tokens are stored in a single znode under
the delegation token root znode? For that we will have to take care that the size a data in
a single znode does not exceed ~500KB (ZK is supposed to support upto 1MB).

We already have serialization formats defined for the stuff we store today. So you can re-use
them. For ones that dont exist, I would suggest creating PB objects. eg. version info.

> 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
>         Attachments: YARN-1307.1.patch, YARN-1307.2.patch
>
>
> 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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