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Date: Wed, 25 Nov 2009 21:58:39 +0000 (UTC)
From: "Chris Douglas (JIRA)" <jira@apache.org>
To: mapreduce-issues@hadoop.apache.org
Subject: [jira] Commented: (MAPREDUCE-1182) Reducers fail with
 OutOfMemoryError while copying Map outputs
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    [ https://issues.apache.org/jira/browse/MAPREDUCE-1182?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12782643#action_12782643 ] 

Chris Douglas commented on MAPREDUCE-1182:
------------------------------------------

Thanks to Amareshwari for testing this at scale

> Reducers fail with OutOfMemoryError while copying Map outputs
> -------------------------------------------------------------
>
>                 Key: MAPREDUCE-1182
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-1182
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>            Reporter: Chandra Prakash Bhagtani
>            Assignee: Chandra Prakash Bhagtani
>            Priority: Blocker
>             Fix For: 0.20.2
>
>         Attachments: HADOOP-6357.patch, M1182-0.patch, M1182-0v20.patch, M1182-1.patch, M1182-1v20.patch
>
>
> Reducers fail while copying Map outputs with following exception
> java.lang.OutOfMemoryError: Java heap space at org.apache.hadoop.mapred.ReduceTask$ReduceCopier$MapOutputCopier.shuffleInMemory(ReduceTask.java:1539) at org.apache.hadoop.mapred.ReduceTask$ReduceCopier$MapOutputCopier.getMapOutput(ReduceTask.java:1432) at org.apache.hadoop.mapred.ReduceTask$ReduceCopier$MapOutputCopier.copyOutput(ReduceTask.java:1285) at org.apache.hadoop.mapred.ReduceTask$ReduceCopier$MapOutputCopier.run(ReduceTask.java:1216) ,Error:
> Reducer's memory usage keeps on increasing and ultimately exceeds -Xmx value  
> I even tried with -Xmx6.5g to each reducer but it's still failing 
> While looking into the reducer logs, I found that reducers were doing shuffleInMemory every time, rather than doing shuffleOnDisk

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