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https://issues.apache.org/jira/browse/HADOOP-4620?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Ravi Gummadi updated HADOOP-4620:
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Attachment: HADOOP-4620.patch
Attached the patch HADOOP-4620.patch that
(1) solves the hanging problem on map side with empty input and nonempty output
--- generates output properly to intermediate files similar to other map tasks.
(2) solves the problem of hanging reducer with empty input to reduce task and
nonempty output --- doesn't generate output if input to reduce task is empty.
Please review the patch and provide your comments. Thanks.
> Streaming mapper never completes if the mapper does not write to stdout
> -----------------------------------------------------------------------
>
> Key: HADOOP-4620
> URL: https://issues.apache.org/jira/browse/HADOOP-4620
> Project: Hadoop Core
> Issue Type: Bug
> Components: mapred
> Affects Versions: 0.17.2
> Reporter: Runping Qi
> Assignee: Ravi Gummadi
> Attachments: HADOOP-4620.patch, solves_mapper_4620.patch
>
>
> A mapper of a streaming job has empty input data and thus it produces no
> output.
> The task never completes.
> The following are the last two lines from the task log:
> 2008-11-07 21:59:48,254 INFO org.apache.hadoop.streaming.PipeMapRed:
> PipeMapRed exec [/usr/bin/perl, xxx]
> 2008-11-07 21:59:48,330 INFO org.apache.hadoop.streaming.PipeMapRed:
> mapRedFinished
>
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