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https://issues.apache.org/jira/browse/MAPREDUCE-5168?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13636105#comment-13636105
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Hadoop QA commented on MAPREDUCE-5168:
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{color:green}+1 overall{color}. Here are the results of testing the latest
attachment
http://issues.apache.org/jira/secure/attachment/12579479/MAPREDUCE-5168.patch
against trunk revision .
{color:green}+1 @author{color}. The patch does not contain any @author
tags.
{color:green}+1 tests included{color}. The patch appears to include 1 new
or modified test files.
{color:green}+1 javac{color}. The applied patch does not increase the
total number of javac compiler warnings.
{color:green}+1 javadoc{color}. The javadoc tool did not generate any
warning messages.
{color:green}+1 eclipse:eclipse{color}. The patch built with
eclipse:eclipse.
{color:green}+1 findbugs{color}. The patch does not introduce any new
Findbugs (version 1.3.9) warnings.
{color:green}+1 release audit{color}. The applied patch does not increase
the total number of release audit warnings.
{color:green}+1 core tests{color}. The patch passed unit tests in
hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core.
{color:green}+1 contrib tests{color}. The patch passed contrib unit tests.
Test results:
https://builds.apache.org/job/PreCommit-MAPREDUCE-Build/3537//testReport/
Console output:
https://builds.apache.org/job/PreCommit-MAPREDUCE-Build/3537//console
This message is automatically generated.
> Reducer can OOM during shuffle because on-disk output stream not released
> -------------------------------------------------------------------------
>
> Key: MAPREDUCE-5168
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-5168
> Project: Hadoop Map/Reduce
> Issue Type: Bug
> Components: mrv2
> Affects Versions: 0.23.7, 2.0.5-beta
> Reporter: Jason Lowe
> Assignee: Jason Lowe
> Priority: Critical
> Attachments: MAPREDUCE-5168.patch
>
>
> If a reducer needs to shuffle a map output to disk, it opens an output stream
> and writes the data to disk. However it does not release the reference to
> the output stream within the MapOutput, and the output stream can have a 128K
> buffer attached to it. If enough of these on-disk outputs are queued up
> waiting to be merged, it can cause the reducer to OOM during the shuffle
> phase. In one case I saw there were 1200 on-disk outputs queued up to be
> merged, leading to an extra 150MB of pressure on the heap due to the output
> stream buffers that were no longer necessary.
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