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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 00:34:51 GMT

    [ https://issues.apache.org/jira/browse/YARN-1574?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13866111#comment-13866111
] 

Karthik Kambatla commented on YARN-1574:
----------------------------------------

Approach looks reasonable. Comments:
# It is probably better to cast to Service instead of AbstractService.
{code}
+    rmDispatcher = setupDispatcher();
+    rmContext.setDispatcher(rmDispatcher);
+    ((AbstractService)rmDispatcher).init(this.conf);
+    ((AbstractService)rmDispatcher).start();
{code}
# In the above snippet, I would update rmDispatcher and rmContext.setDispatcher() after the
init and start are called. That way there won't be a window where the dispatcher is not started
and hence can't handle events. 
# Can we also make sure that callers of rmContext.getDispatcher() are not caching the dispatcher?
Even though, most callers are currently in RMActiveServices and not Always-On, we should make
sure they don't cache. We should probably update rmContext.getDispatcher() documentation also
to reflect that? 

> 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
>
>
> 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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