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From "Devaraj Das (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-2095) Reducer failed due to Out ofMemory
Date Thu, 25 Oct 2007 05:42:50 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-2095?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12537499
] 

Devaraj Das commented on HADOOP-2095:
-------------------------------------

My hunch is this that we are ending up with too many files in the ramfs (the map outputs for
the failing reduce are small in size). So when merge is initiated on those files, we end up
creating too many codecs for decompressing the files, and since they are native, we encounter
OOM. So one way to validate this is to decrease the value of mapred.inmem.merge.threshold
(defaults to 1000) to something like 200 and then see whether the OOM goes away. The other
alternative is to increase the heap size per task.

> Reducer failed due to Out ofMemory
> ----------------------------------
>
>                 Key: HADOOP-2095
>                 URL: https://issues.apache.org/jira/browse/HADOOP-2095
>             Project: Hadoop
>          Issue Type: Bug
>          Components: mapred
>            Reporter: Runping Qi
>
> One of the reducers of my job failed with the following exceptions.
> The failure caused the whole job fail eventually.
> Java heapsize was 768MB and sort.io.mb was 140.
> 2007-10-23 19:24:06,100 WARN org.apache.hadoop.mapred.ReduceTask: task_200710231912_0001_r_000020_2
Intermediate Merge of the inmemory files threw an exception: java.lang.OutOfMemoryError: Java
heap space
> 	at org.apache.hadoop.io.compress.DecompressorStream.(DecompressorStream.java:43)
> 	at org.apache.hadoop.io.compress.DefaultCodec.createInputStream(DefaultCodec.java:71)
> 	at org.apache.hadoop.io.SequenceFile$Reader.init(SequenceFile.java:1345)
> 	at org.apache.hadoop.io.SequenceFile$Reader.(SequenceFile.java:1231)
> 	at org.apache.hadoop.io.SequenceFile$Reader.(SequenceFile.java:1154)
> 	at org.apache.hadoop.io.SequenceFile$Sorter$SegmentDescriptor.nextRawKey(SequenceFile.java:2726)
> 	at org.apache.hadoop.io.SequenceFile$Sorter$MergeQueue.merge(SequenceFile.java:2543)
> 	at org.apache.hadoop.io.SequenceFile$Sorter.merge(SequenceFile.java:2297)
> 	at org.apache.hadoop.mapred.ReduceTask$ReduceCopier$InMemFSMergeThread.run(ReduceTask.java:1311)
> 2007-10-23 19:24:06,102 INFO org.apache.hadoop.mapred.ReduceTask: task_200710231912_0001_r_000020_2
done copying task_200710231912_0001_m_001428_0 output .
> 2007-10-23 19:24:06,185 INFO org.apache.hadoop.fs.FileSystem: Initialized InMemoryFileSystem:
ramfs://mapoutput31952838/task_200710231912_0001_r_000020_2/map_1423.out-0 of size (in bytes):
209715200
> 2007-10-23 19:24:06,193 ERROR org.apache.hadoop.mapred.ReduceTask: Map output copy failure:
java.lang.NullPointerException
> 	at org.apache.hadoop.fs.InMemoryFileSystem$RawInMemoryFileSystem$FileAttributes.access$300(InMemoryFileSystem.java:366)
> 	at org.apache.hadoop.fs.InMemoryFileSystem$RawInMemoryFileSystem$InMemoryFileStatus.(InMemoryFileSystem.java:378)
> 	at org.apache.hadoop.fs.InMemoryFileSystem$RawInMemoryFileSystem.getFileStatus(InMemoryFileSystem.java:283)
> 	at org.apache.hadoop.fs.FilterFileSystem.getFileStatus(FilterFileSystem.java:251)
> 	at org.apache.hadoop.fs.FileSystem.getLength(FileSystem.java:449)
> 	at org.apache.hadoop.mapred.ReduceTask$ReduceCopier$MapOutputCopier.copyOutput(ReduceTask.java:738)
> 	at org.apache.hadoop.mapred.ReduceTask$ReduceCopier$MapOutputCopier.run(ReduceTask.java:665)
> 2007-10-23 19:24:06,193 INFO org.apache.hadoop.mapred.ReduceTask: task_200710231912_0001_r_000020_2
Copying task_200710231912_0001_m_001215_0 output from xxx
> 2007-10-23 19:24:06,188 INFO org.apache.hadoop.mapred.ReduceTask: task_200710231912_0001_r_000020_2
Copying task_200710231912_0001_m_001211_0 output from xxx
> 2007-10-23 19:24:06,185 ERROR org.apache.hadoop.mapred.ReduceTask: Map output copy failure:
java.lang.NullPointerException
> 	at org.apache.hadoop.fs.InMemoryFileSystem$RawInMemoryFileSystem$InMemoryOutputStream.close(InMemoryFileSystem.java:161)
> 	at org.apache.hadoop.fs.FSDataOutputStream$PositionCache.close(FSDataOutputStream.java:49)
> 	at org.apache.hadoop.fs.FSDataOutputStream.close(FSDataOutputStream.java:64)
> 	at org.apache.hadoop.fs.ChecksumFileSystem$ChecksumFSOutputSummer.close(ChecksumFileSystem.java:312)
> 	at org.apache.hadoop.fs.FSDataOutputStream$PositionCache.close(FSDataOutputStream.java:49)
> 	at org.apache.hadoop.fs.FSDataOutputStream.close(FSDataOutputStream.java:64)
> 	at org.apache.hadoop.mapred.MapOutputLocation.getFile(MapOutputLocation.java:253)
> 	at org.apache.hadoop.mapred.ReduceTask$ReduceCopier$MapOutputCopier.copyOutput(ReduceTask.java:713)
> 	at org.apache.hadoop.mapred.ReduceTask$ReduceCopier$MapOutputCopier.run(ReduceTask.java:665)
> 2007-10-23 19:24:06,199 INFO org.apache.hadoop.mapred.ReduceTask: task_200710231912_0001_r_000020_2
Copying task_200710231912_0001_m_001247_0 output from .
> 2007-10-23 19:24:06,200 ERROR org.apache.hadoop.mapred.ReduceTask: Map output copy failure:
java.lang.NullPointerException
> 	at org.apache.hadoop.fs.InMemoryFileSystem$RawInMemoryFileSystem$FileAttributes.access$300(InMemoryFileSystem.java:366)
> 	at org.apache.hadoop.fs.InMemoryFileSystem$RawInMemoryFileSystem$InMemoryFileStatus.(InMemoryFileSystem.java:378)
> 	at org.apache.hadoop.fs.InMemoryFileSystem$RawInMemoryFileSystem.getFileStatus(InMemoryFileSystem.java:283)
> 	at org.apache.hadoop.fs.FilterFileSystem.getFileStatus(FilterFileSystem.java:251)
> 	at org.apache.hadoop.fs.FileSystem.getLength(FileSystem.java:449)
> 	at org.apache.hadoop.mapred.ReduceTask$ReduceCopier$MapOutputCopier.copyOutput(ReduceTask.java:738)
> 	at org.apache.hadoop.mapred.ReduceTask$ReduceCopier$MapOutputCopier.run(ReduceTask.java:665)
> 2007-10-23 19:24:06,204 INFO org.apache.hadoop.mapred.ReduceTask: task_200710231912_0001_r_000020_2
Copying task_200710231912_0001_m_001422_0 output from .
> 2007-10-23 19:24:06,207 ERROR org.apache.hadoop.mapred.ReduceTask: Map output copy failure:
java.lang.NullPointerException
> 	at org.apache.hadoop.fs.InMemoryFileSystem$RawInMemoryFileSystem$FileAttributes.access$300(InMemoryFileSystem.java:366)
> 	at org.apache.hadoop.fs.InMemoryFileSystem$RawInMemoryFileSystem$InMemoryFileStatus.(InMemoryFileSystem.java:378)
> 	at org.apache.hadoop.fs.InMemoryFileSystem$RawInMemoryFileSystem.getFileStatus(InMemoryFileSystem.java:283)
> 	at org.apache.hadoop.fs.FilterFileSystem.getFileStatus(FilterFileSystem.java:251)
> 	at org.apache.hadoop.fs.FileSystem.getLength(FileSystem.java:449)
> 	at org.apache.hadoop.mapred.ReduceTask$ReduceCopier$MapOutputCopier.copyOutput(ReduceTask.java:738)
> 	at org.apache.hadoop.mapred.ReduceTask$ReduceCopier$MapOutputCopier.run(ReduceTask.java:665)
> 2007-10-23 19:24:06,209 INFO org.apache.hadoop.mapred.ReduceTask: task_200710231912_0001_r_000020_2
Copying task_200710231912_0001_m_001278_0 output from .
> 2007-10-23 19:24:06,198 WARN org.apache.hadoop.mapred.TaskTracker: Error running child
> java.io.IOException: task_200710231912_0001_r_000020_2The reduce copier failed
> 	at org.apache.hadoop.mapred.ReduceTask.run(ReduceTask.java:253)
> 	at org.apache.hadoop.mapred.TaskTracker$Child.main(TaskTracker.java:1760)
> 2007-10-23 19:24:06,198 ERROR org.apache.hadoop.mapred.ReduceTask: Map output copy failure:
java.lang.NullPointerException
> 	at org.apache.hadoop.fs.InMemoryFileSystem$RawInMemoryFileSystem$FileAttributes.access$300(InMemoryFileSystem.java:366)
> 	at org.apache.hadoop.fs.InMemoryFileSystem$RawInMemoryFileSystem$InMemoryFileStatus.(InMemoryFileSystem.java:378)
> 	at org.apache.hadoop.fs.InMemoryFileSystem$RawInMemoryFileSystem.getFileStatus(InMemoryFileSystem.java:283)
> 	at org.apache.hadoop.fs.FilterFileSystem.getFileStatus(FilterFileSystem.java:251)
> 	at org.apache.hadoop.fs.FileSystem.getLength(FileSystem.java:449)
> 	at org.apache.hadoop.mapred.ReduceTask$ReduceCopier$MapOutputCopier.copyOutput(ReduceTask.java:738)
> 	at org.apache.hadoop.mapred.ReduceTask$ReduceCopier$MapOutputCopier.run(ReduceTask.java:665)
> 2007-10-23 19:24:06,231 INFO org.apache.hadoop.mapred.ReduceTask: task_200710231912_0001_r_000020_2
Copying task_200710231912_0001_m_001531_0 output from .
> 2007-10-23 19:24:06,197 ERROR org.apache.hadoop.mapred.ReduceTask: Map output copy failure:
java.lang.NullPointerException
> 	at org.apache.hadoop.fs.InMemoryFileSystem$RawInMemoryFileSystem$FileAttributes.access$300(InMemoryFileSystem.java:366)
> 	at org.apache.hadoop.fs.InMemoryFileSystem$RawInMemoryFileSystem$InMemoryFileStatus.(InMemoryFileSystem.java:378)
> 	at org.apache.hadoop.fs.InMemoryFileSystem$RawInMemoryFileSystem.getFileStatus(InMemoryFileSystem.java:283)
> 	at org.apache.hadoop.fs.FilterFileSystem.getFileStatus(FilterFileSystem.java:251)
> 	at org.apache.hadoop.fs.FileSystem.getLength(FileSystem.java:449)
> 	at org.apache.hadoop.mapred.ReduceTask$ReduceCopier$MapOutputCopier.copyOutput(ReduceTask.java:738)
> 	at org.apache.hadoop.mapred.ReduceTask$ReduceCopier$MapOutputCopier.run(ReduceTask.java:665)
> 2007-10-23 19:24:06,237 INFO org.apache.hadoop.mapred.ReduceTask: task_200710231912_0001_r_000020_2
Copying task_200710231912_0001_m_001227_0 output from .
> 2007-10-23 19:24:06,196 ERROR org.apache.hadoop.mapred.ReduceTask: Map output copy failure:
java.lang.NullPointerException
> 	at org.apache.hadoop.fs.InMemoryFileSystem$RawInMemoryFileSystem$FileAttributes.access$300(InMemoryFileSystem.java:366)
> 	at org.apache.hadoop.fs.InMemoryFileSystem$RawInMemoryFileSystem$InMemoryFileStatus.(InMemoryFileSystem.java:378)
> 	at org.apache.hadoop.fs.InMemoryFileSystem$RawInMemoryFileSystem.getFileStatus(InMemoryFileSystem.java:283)
> 	at org.apache.hadoop.fs.FilterFileSystem.getFileStatus(FilterFileSystem.java:251)
> 	at org.apache.hadoop.fs.FileSystem.getLength(FileSystem.java:449)
> 	at org.apache.hadoop.mapred.ReduceTask$ReduceCopier$MapOutputCopier.copyOutput(ReduceTask.java:738)
> 	at org.apache.hadoop.mapred.ReduceTask$ReduceCopier$MapOutputCopier.run(ReduceTask.java:665)

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