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From "Amar Kamat (JIRA)" <j...@apache.org>
Subject [jira] Updated: (HADOOP-5746) Errors encountered in MROutputThread after the last map/reduce call can go undetected
Date Wed, 03 Jun 2009 06:18:07 GMT

     [ https://issues.apache.org/jira/browse/HADOOP-5746?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Amar Kamat updated HADOOP-5746:

    Attachment: 5746-testcase.patch

Attaching the patch [5746.6.patch]. It looks like its a very timing issue to reproduce/test
this bug. The problem occurs when the pipe process finishes off and then the output thread
cranks up with some exception (like fs errors). 
Attaching a framework change [5746-reproduce.1.patch] and a testcase [/5746-testcase.patch]
to verify the fix. The caller of {{PipeMapRed.waitOutputThreads()}} i.e {{PipeMapRed.mapRedFinished()}}
simply ignores IOException hence changed the exception to {{RuntimeException}}. I dont know
why PipeMapRed.mapRedFinished() ignores IOException. But for now I have kept it as it is.

> Errors encountered in MROutputThread after the last map/reduce call can go undetected
> -------------------------------------------------------------------------------------
>                 Key: HADOOP-5746
>                 URL: https://issues.apache.org/jira/browse/HADOOP-5746
>             Project: Hadoop Core
>          Issue Type: Bug
>          Components: contrib/streaming
>            Reporter: Devaraj Das
>             Fix For: 0.21.0
>         Attachments: 5746-reproduce.1.patch, 5746-testcase.patch, 5746.1.patch, 5746.6.patch
> The framework map/reduce bridge methods make a check at the beginning of the respective
methods whether _MROutputThread_ encountered an exception while writing keys/values that the
streaming process emitted. However, if the exception happens in _MROutputThread_ after the
last call to the map/reduce method, the exception goes undetected. An example of such an exception
is an exception from the _DFSClient_ that fails to write to a file on the HDFS.

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