[jira] [Commented] (MAPREDUCE-4374) Fix child task environment variable config and add support for Windows

["Bikas Saha (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/MAPREDUCE-4374?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13427851#comment-13427851 ] 

Bikas Saha commented on MAPREDUCE-4374:
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bq.Notice this is tmp directory. On Linux /tmp exists by default which is not the case on Windows.
I think this is not limited to /tmp. It could be any directory set in the config.
btw, in the if condition is tmpDir exists then the check for it being a dir is skipped I think.

bq. Let’s not push this to Shell as I think the code is simply enough to be understood and we can work towards a better abstraction for this (handling ‘set’ vs ‘export’) in the future.
I see what the issue is. At the same time, this code is duplicated in 4 different places. So IMO, it makes sense to put these in a helper method call. When we make a better abstraction, we will know the single place to look for the old code instead of multiple places. Thoughts?
                
> Fix child task environment variable config and add support for Windows
> ----------------------------------------------------------------------
>
>                 Key: MAPREDUCE-4374
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-4374
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>    Affects Versions: 1-win
>            Reporter: Chuan Liu
>            Assignee: Chuan Liu
>            Priority: Minor
>         Attachments: MAPREDUCE-4374-branch-1-win-2.patch, MAPREDUCE-4374-branch-1-win.patch
>
>
> In HADOOP-2838, a new feature was introduced to set environment variables via the Hadoop config 'mapred.child.env' for child tasks. There are some further fixes and improvements around this feature, e.g. HADOOP-5981 were a bug fix; MAPREDUCE-478 broke the config into 'mapred.map.child.env' and 'mapred.reduce.child.env'.  However the current implementation is still not complete. It does not match its documentation or original intend as I believe. Also, by using ‘:’ (colon) and ‘;’ (semicolon) in the configuration syntax, we will have problems using them on Windows because ‘:’ appears very often in Windows path as in “C:\”, and environment variables are used very often to hold path names. The Jira is created to fix the problem and provide support on Windows.

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