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Posted to mapreduce-issues@hadoop.apache.org by "Thomas Graves (JIRA)" <ji...@apache.org> on 2013/05/14 15:41:16 UTC

[jira] [Commented] (MAPREDUCE-5124) AM lacks flow control for task events

    [ https://issues.apache.org/jira/browse/MAPREDUCE-5124?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13657057#comment-13657057 ] 

Thomas Graves commented on MAPREDUCE-5124:
------------------------------------------

Can you please give more details.  When you say it should have the capacity for handling event per second what does that mean?  Is it telling the tasks to stop backoff?
                
> 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
>         Attachments: 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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