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From "Owen O'Malley (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-2095) Reducer failed due to Out ofMemory
Date Mon, 28 Apr 2008 23:13:56 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-2095?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12592925#action_12592925
] 

Owen O'Malley commented on HADOOP-2095:
---------------------------------------

It is worth noting that we'd need to reserve mapred.reduce.parallel.copies (default 5, but
20 on yahoo's clusters) extra codecs for decompressing on the fly. It isn't clear to me that
it would be a win having the codec owned by the copier thread rather than the merger. 

You would also need to add a header that gives the uncompressed size of the map outputs, so
that the reducer knows how big the uncompressed file is.

Of course getting rid of the 4 compression codecs using something like HADOOP-3315, would
help a *lot*.

> Reducer failed due to Out ofMemory
> ----------------------------------
>
>                 Key: HADOOP-2095
>                 URL: https://issues.apache.org/jira/browse/HADOOP-2095
>             Project: Hadoop Core
>          Issue Type: Bug
>          Components: mapred
>    Affects Versions: 0.15.0
>            Reporter: Runping Qi
>            Assignee: Arun C Murthy
>         Attachments: HADOOP-2095_CompressedBytesWithCodecPool.patch, HADOOP-2095_debug.patch
>
>
> 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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