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From "Amareshwari Sriramadasu (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-6357) Reducers fail with OutOfMemoryError while copying Map outputs
Date Tue, 03 Nov 2009 10:24:01 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-6357?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12773004#action_12773004

Amareshwari Sriramadasu commented on HADOOP-6357:

Can you give more details like the values for configuration parameters such as mapred.job.shuffle.input.buffer.percent
and mapred.inmem.merge.threshold, if you are not using default values? 

> Reducers fail with OutOfMemoryError while copying Map outputs
> -------------------------------------------------------------
>                 Key: HADOOP-6357
>                 URL: https://issues.apache.org/jira/browse/HADOOP-6357
>             Project: Hadoop Common
>          Issue Type: Bug
>    Affects Versions: 0.20.0
>            Reporter: Chandra Prakash Bhagtani
>             Fix For: 0.20.0
> 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)
> 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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