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From "Jason Lowe (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (MAPREDUCE-5124) AM lacks flow control for task events
Date Tue, 05 Sep 2017 19:50:00 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-5124?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16154189#comment-16154189
] 

Jason Lowe commented on MAPREDUCE-5124:
---------------------------------------

Ah, sorry, I thought we were still worrying about how to keep the AM from exploding.  Sure,
I could see a dynamic heartbeat still being useful once the flow control problem is addressed.
 Even with the current async processing without flow control we could feedback to the task
information on how long to wait until the next heartbeat (e.g.: leverage the current AsyncDispatcher
event queue size to scale the next task heartbeat interval accordingly) which could help avoid
continued heartbeat pileups for large jobs.

> AM lacks flow control for task events
> -------------------------------------
>
>                 Key: MAPREDUCE-5124
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-5124
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>          Components: mr-am
>    Affects Versions: 2.0.3-alpha, 0.23.5
>            Reporter: Jason Lowe
>            Assignee: Haibo Chen
>         Attachments: MAPREDUCE-5124-proto.2.txt, MAPREDUCE-5124-prototype.txt
>
>
> The AM does not have any flow control to limit the incoming rate of events from tasks.
 If the AM is unable to keep pace with the rate of incoming events for a sufficient period
of time then it will eventually exhaust the heap and crash.  MAPREDUCE-5043 addressed a major
bottleneck for event processing, but the AM could still get behind if it's starved for CPU
and/or handling a very large job with tens of thousands of active tasks.



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