[jira] Updated: (HADOOP-5746) Errors encountered in MROutputThread after the last map/reduce call can go undetected

["Amar Kamat (JIRA)" <ji...@apache.org>]

     [ 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
                5746-reproduce.1.patch
                5746.6.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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