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https://issues.apache.org/jira/browse/MAPREDUCE-5028?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13587448#comment-13587448
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Chris Douglas commented on MAPREDUCE-5028:
------------------------------------------
bq. getLength() returns the size of the entire buffer, and not just the
remaining part of the buffer
Just to be clear, it's not the size of the backing array, but "the index one
greater than the last valid character in the input stream buffer."
(ByteArrayInputStream) The change to {{DataInputBuffer}} implies the former,
which is inaccurate.
The corrects several misuses of DataInputBuffer, which is great. There's
another misuse at {{ReduceContextImpl.ValueIterator::next}} that could be
included with these changes.
Most of this code doesn't check for overflow; it wasn't written for extremely
large buffers. Just glancing at related code, MapTask.InMemValBytes contains
code that could overflow and I'm sure there are others. Filed MAPREDUCE-5032.
> Maps fail when io.sort.mb is set to high value
> ----------------------------------------------
>
> Key: MAPREDUCE-5028
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-5028
> Project: Hadoop Map/Reduce
> Issue Type: Bug
> Affects Versions: 1.1.1
> Reporter: Karthik Kambatla
> Assignee: Karthik Kambatla
> Priority: Critical
> Attachments: mr-5028-branch1.patch
>
>
> Verified the problem exists on branch-1 with the following configuration:
> Pseudo-dist mode: 2 maps/ 1 reduce, mapred.child.java.opts=-Xmx2048m,
> io.sort.mb=1280, dfs.block.size=2147483648
> Run teragen to generate 4 GB data
> Maps fail when you run wordcount on this configuration with the following
> error:
> {noformat}
> java.io.IOException: Spill failed
> at
> org.apache.hadoop.mapred.MapTask$MapOutputBuffer.collect(MapTask.java:1031)
> at
> org.apache.hadoop.mapred.MapTask$NewOutputCollector.write(MapTask.java:692)
> at
> org.apache.hadoop.mapreduce.TaskInputOutputContext.write(TaskInputOutputContext.java:80)
> at
> org.apache.hadoop.examples.WordCount$TokenizerMapper.map(WordCount.java:45)
> at
> org.apache.hadoop.examples.WordCount$TokenizerMapper.map(WordCount.java:34)
> at org.apache.hadoop.mapreduce.Mapper.run(Mapper.java:144)
> at org.apache.hadoop.mapred.MapTask.runNewMapper(MapTask.java:766)
> at org.apache.hadoop.mapred.MapTask.run(MapTask.java:370)
> at org.apache.hadoop.mapred.Child$4.run(Child.java:255)
> at java.security.AccessController.doPrivileged(Native Method)
> at javax.security.auth.Subject.doAs(Subject.java:396)
> at
> org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1149)
> at org.apache.hadoop.mapred.Child.main(Child.java:249)
> Caused by: java.io.EOFException
> at java.io.DataInputStream.readInt(DataInputStream.java:375)
> at org.apache.hadoop.io.IntWritable.readFields(IntWritable.java:38)
> at
> org.apache.hadoop.io.serializer.WritableSerialization$WritableDeserializer.deserialize(WritableSerialization.java:67)
> at
> org.apache.hadoop.io.serializer.WritableSerialization$WritableDeserializer.deserialize(WritableSerialization.java:40)
> at
> org.apache.hadoop.mapreduce.ReduceContext.nextKeyValue(ReduceContext.java:116)
> at
> org.apache.hadoop.mapreduce.ReduceContext.nextKey(ReduceContext.java:92)
> at org.apache.hadoop.mapreduce.Reducer.run(Reducer.java:175)
> at
> org.apache.hadoop.mapred.Task$NewCombinerRunner.combine(Task.java:1505)
> at
> org.apache.hadoop.mapred.MapTask$MapOutputBuffer.sortAndSpill(MapTask.java:1438)
> at
> org.apache.hadoop.mapred.MapTask$MapOutputBuffer.access$1800(MapTask.java:855)
> at
> org.apache.hadoop.mapred.MapTask$MapOutputBuffer$SpillThread.run(MapTask.java:1346)
> {noformat}
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