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From "Chandra Prakash Bhagtani (JIRA)" <j...@apache.org>
Subject [jira] Created: (HADOOP-6357) Reducers fail with OutOfMemoryError while copying Map outputs
Date Tue, 03 Nov 2009 10:07:59 GMT
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

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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