[jira] Resolved: (HADOOP-960) Incorrect number of map tasks when there are multiple input files

["Owen O'Malley (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HADOOP-960?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Owen O'Malley resolved HADOOP-960.
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    Resolution: Won't Fix

This may not be documented well enough, but it is not a bug. The rules for picking input split sizes are complicated, but usually a split is 1 dfs block. The number of maps requested is a hint to the InputFormat, nothing else. To get the behavior that you want, you can set mapred.min.split.size to a large value. It will force the splits to contain the entire contents of a single file.

> Incorrect number of map tasks when there are multiple input files
> -----------------------------------------------------------------
>
>                 Key: HADOOP-960
>                 URL: https://issues.apache.org/jira/browse/HADOOP-960
>             Project: Hadoop
>          Issue Type: Bug
>    Affects Versions: 0.10.1
>            Reporter: Andrew McNabb
>
> This problem happens with hadoop-streaming and possibly elsewhere.  If there are 5 input files, it will create 130 map tasks, even if mapred.map.tasks=128.  The number of map tasks is incorrectly set to a multiple of the number of files.  (I wrote a much more complete bug report, but Jira lost it when it had an error, so I'm not in the mood to write it all again)

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