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Posted to mapreduce-issues@hadoop.apache.org by "Jason Lowe (JIRA)" <ji...@apache.org> on 2013/02/25 21:50:12 UTC

[jira] [Commented] (MAPREDUCE-5027) Shuffle does not limit number of outstanding connections

    [ https://issues.apache.org/jira/browse/MAPREDUCE-5027?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13586267#comment-13586267 ] 

Jason Lowe commented on MAPREDUCE-5027:
---------------------------------------

AFAIK there is no built-in way to have Netty automatically limit the number of active client connections.  A quick search on the net indicates one way this is handled is to simply close the extra connections as soon as they are created once we get past a specified number of active connections.
                
> Shuffle does not limit number of outstanding connections
> --------------------------------------------------------
>
>                 Key: MAPREDUCE-5027
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-5027
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>    Affects Versions: 2.0.3-alpha, 0.23.5
>            Reporter: Jason Lowe
>
> The ShuffleHandler does not have any configurable limits to the number of outstanding connections allowed.  Therefore a node with many map outputs and many reducers in the cluster trying to fetch those outputs can exhaust a nodemanager out of file descriptors.

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