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From "Vinod Kumar Vavilapalli (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (YARN-1029) Allow embedding leader election into the RM
Date Tue, 17 Dec 2013 00:02:10 GMT

    [ https://issues.apache.org/jira/browse/YARN-1029?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13849898#comment-13849898
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Vinod Kumar Vavilapalli commented on YARN-1029:
-----------------------------------------------

bq. I'm also not sure why we want to preserve the "external ZKFC" option - per above it's
a more complicated deployment scenario and seems to offer little tangible benefit.
It was confusing to me when both this and YARN-1177 were filed. The ZKStateStore implementation
did implement a fence operation (YARN-1222) but it wasn't integrated with the leader election
(AFAIU) even in the current set of patches.

bq. This is true when using the ZKRMStateStore, but there are other stores, like the FileSystemRMStateStore
which don't introduce a ZK dependency.
We shipped FileSystemRMStateStore as just a backing store, there isn't a way to fence multiple
FS stores and so it cannot be used for fail-over.

Agree with the general suggestion - If we use the leader election by the ZK client itself,
then we don't need a separate ZKFC. So let's do that and close YARN-1177 as won't fix?

> Allow embedding leader election into the RM
> -------------------------------------------
>
>                 Key: YARN-1029
>                 URL: https://issues.apache.org/jira/browse/YARN-1029
>             Project: Hadoop YARN
>          Issue Type: Sub-task
>            Reporter: Bikas Saha
>            Assignee: Karthik Kambatla
>         Attachments: embedded-zkfc-approach.patch, yarn-1029-0.patch, yarn-1029-0.patch,
yarn-1029-approach.patch
>
>
> It should be possible to embed common ActiveStandyElector into the RM such that ZooKeeper
based leader election and notification is in-built. In conjunction with a ZK state store,
this configuration will be a simple deployment option.



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