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From "David Bowen (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-968) Reduce shuffle and merge should be done a child JVM
Date Tue, 17 Apr 2007 18:17:15 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-968?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12489490
] 

David Bowen commented on HADOOP-968:
------------------------------------


Devaraj, please can you clarify what you fixed with regard to the lack of calls to stopMonitoring?
 I think you're right that it is a problem, but I would expect the fix to be to change the
Timer constructor in o.a.h.metrics.spi.AbstractMetricsContext.  Instead of the zero-arg constructor
we should use the two arg constructor that takes a thread name and a boolean isDaemon.  I
didn't see this change in the patch.



> Reduce shuffle and merge should be done a child JVM
> ---------------------------------------------------
>
>                 Key: HADOOP-968
>                 URL: https://issues.apache.org/jira/browse/HADOOP-968
>             Project: Hadoop
>          Issue Type: Improvement
>          Components: mapred
>    Affects Versions: 0.10.1
>            Reporter: Owen O'Malley
>         Assigned To: Devaraj Das
>             Fix For: 0.13.0
>
>         Attachments: 968-reindent.patch, 968-with-metrics-fix.patch, 968.apr06.patch,
968.apr10.patch, 968.apr14.patch, 968.apr14.patch, 968.patch
>
>
> The Reduce's shuffle and initial merge is done in the TaskTracker's JVM. It would be
better to have it run in the Task's child JVM. The advantages are:
>   1. The class path and environment would be set up correctly.
>   2. User code doesn't need to be loaded into the TaskTracker.
>   3. Lower memory usage and contention in the TaskTracker.

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