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From "Ravi Gummadi (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-4620) Streaming mapper never completes if the mapper does not write to stdout
Date Wed, 03 Dec 2008 05:38:44 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-4620?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12652689#action_12652689

Ravi Gummadi commented on HADOOP-4620:

So there is no issue of tasks hanging forever(even if the size of the map output is 0 bytes).
I agree that the message "mapRedFinished" is displayed before output thread and error thread
have completed their work. Log messages will be changed to be displayed appopriately.

Otherwise, please provide a testcase that reproduces the problem of Map Task hanging. I am
not able to reproduce the problem of hanging map task.

> 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
> 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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