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https://issues.apache.org/jira/browse/HADOOP-1152?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Devaraj Das updated HADOOP-1152:
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Attachment: 1152.workaround.patch
Actually the problem might not be in the rename. The NPE should not happen in
the first place.
Here is a patch that will kill the task if it ever encounters a NPE in the
affected part of the code. It will also log the state of the ramfs in terms of
the files it currently has and their lengths. It will also log a diagnostic
message which you would see in the web ui for the killed task. Please upload
those log messages whenever you see tasks failing with this exception.
> Reduce task hang failing in MapOutputCopier.copyOutput
> ------------------------------------------------------
>
> Key: HADOOP-1152
> URL: https://issues.apache.org/jira/browse/HADOOP-1152
> Project: Hadoop
> Issue Type: Bug
> Components: mapred
> Reporter: Koji Noguchi
> Assigned To: Tahir Hashmi
> Attachments: 1152.workaround.patch
>
>
> We had couple of reduce tasks hang repeating the output below.
> 2007-03-22 23:57:16,296 WARN org.apache.hadoop.mapred.TaskRunner:
> java.io.IOException: Path
> /hadoop/mapred/local/task_0026_r_000307_0/map_7854.out already exists
> at
> org.apache.hadoop.fs.InMemoryFileSystem$RawInMemoryFileSystem.rename(InMemoryFileSystem.java:246)
> at
> org.apache.hadoop.fs.ChecksumFileSystem.rename(ChecksumFileSystem.java:471)
> at
> org.apache.hadoop.mapred.ReduceTaskRunner$MapOutputCopier.copyOutput(ReduceTaskRunner.java:336)
> at
> org.apache.hadoop.mapred.ReduceTaskRunner$MapOutputCopier.run(ReduceTaskRunner.java:274)
> 2007-03-22 23:57:16,296 WARN org.apache.hadoop.mapred.TaskRunner:
> task_0026_r_000307_0 adding host ______ to penalty box, next contact in 192
> seconds
> ===============================
> Before the above output, there was
> 2007-03-22 18:15:24,274 ERROR org.apache.hadoop.mapred.TaskRunner: Map output
> copy failure: java.lang.NullPointerException
> at
> org.apache.hadoop.fs.InMemoryFileSystem$RawInMemoryFileSystem$FileAttributes.access$300(InMemoryFileSystem.java:416)
> at
> org.apache.hadoop.fs.InMemoryFileSystem$RawInMemoryFileSystem.getLength(InMemoryFileSystem.java:286)
> at
> org.apache.hadoop.fs.FilterFileSystem.getLength(FilterFileSystem.java:178)
> at
> org.apache.hadoop.mapred.ReduceTaskRunner$MapOutputCopier.copyOutput(ReduceTaskRunner.java:340)
> at
> org.apache.hadoop.mapred.ReduceTaskRunner$MapOutputCopier.run(ReduceTaskRunner.java:274)
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