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From "Karthik Kambatla (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (YARN-1574) When RM transit from Active to Standby, the same eventDispatcher should not be registered more than once
Date Thu, 09 Jan 2014 03:54:54 GMT

    [ https://issues.apache.org/jira/browse/YARN-1574?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13866282#comment-13866282

Karthik Kambatla commented on YARN-1574:

bq. I think that they are fine because all of them will be re-initiated with new rmContext.
Also, I am curious why this is necessary (make sure that callers are not caching the dispatcher)
since we register the same dispatcher.
That is true for the current approach of destroy-and-recreate that we use for RMActiveServices.
I was wondering about the behavior in the future when we actually support suspend-resume capability
to our services, but I guess then we won't be re-registering handlers either. So, yeah, I
think we are good there.

We should be careful and make sure all AlwaysOn services that register a handler should be
handled in setup dispatcher - may be add comments both at the site of calling setup dispatcher
and javadoc for setup-dispatcher.

Can we add a unit test as well? Add all handlers to the dispatcher and call transitions to
standby and active a couple of times and make sure the number of handlers is right, or something
along those lines?  

> When RM transit from Active to Standby, the same eventDispatcher should not be registered
more than once
> --------------------------------------------------------------------------------------------------------
>                 Key: YARN-1574
>                 URL: https://issues.apache.org/jira/browse/YARN-1574
>             Project: Hadoop YARN
>          Issue Type: Sub-task
>            Reporter: Xuan Gong
>            Assignee: Xuan Gong
>            Priority: Blocker
>         Attachments: YARN-1574.1.patch, YARN-1574.1.patch, YARN-1574.2.patch, YARN-1574.2.patch
> Currently, we move rmDispatcher out of ActiveService. But we still register the Event
dispatcher, such as schedulerDispatcher, RMAppEventDispatcher when we initiate the ActiveService.
> Almost every time when we transit RM from Active to Standby,  we need to initiate the
ActiveService. That means we will register the same event Dispatcher which will cause the
same event will be handled several times.

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