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

["Peter Bacsko (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/MAPREDUCE-5124?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16236220#comment-16236220 ] 

Peter Bacsko commented on MAPREDUCE-5124:
-----------------------------------------

I've got some updates. I tried to use the deferred callback mechanism implemented in HADOOP-11552 and it doesn't work. It's because HADOOP-11552 solved the issue for {{ProtobufRpcEngine}} but MapRed status updates use {{WritableRpcEngine}}. So either we completely drop this approach or implement HADOOP-11552 for Writable RPC calls as well.

> 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: Peter Bacsko
>            Priority: Major
>         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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