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From "Chen He (JIRA)" <j...@apache.org>
Subject [jira] [Assigned] (YARN-2410) Nodemanager ShuffleHandler can easily exhaust file descriptors
Date Wed, 13 Aug 2014 15:22:11 GMT

     [ https://issues.apache.org/jira/browse/YARN-2410?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Chen He reassigned YARN-2410:
-----------------------------

    Assignee: Chen He

> Nodemanager ShuffleHandler can easily exhaust file descriptors
> --------------------------------------------------------------
>
>                 Key: YARN-2410
>                 URL: https://issues.apache.org/jira/browse/YARN-2410
>             Project: Hadoop YARN
>          Issue Type: Bug
>          Components: nodemanager
>    Affects Versions: 2.5.0
>            Reporter: Nathan Roberts
>            Assignee: Chen He
>            Priority: Critical
>
> The async nature of the shufflehandler can cause it to open a huge number of
> file descriptors, when it runs out it crashes.
> Scenario:
> Job with 6K reduces, slow start set to 0.95, about 40 map outputs per node.
> Let's say all 6K reduces hit a node at about same time asking for their
> outputs. Each reducer will ask for all 40 map outputs over a single socket in a
> single request (not necessarily all 40 at once, but with coalescing it is
> likely to be a large number).
> sendMapOutput() will open the file for random reading and then perform an async transfer
of the particular portion of this file(). This will theoretically
> happen 6000*40=240000 times which will run the NM out of file descriptors and cause it
to crash.
> The algorithm should be refactored a little to not open the fds until they're
> actually needed. 



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