[jira] Commented: (MAPREDUCE-890) After HADOOP-4491, the user who started mapred system is not able to run job.

["Vinod K V (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/MAPREDUCE-890?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12745783#action_12745783 ] 

Vinod K V commented on MAPREDUCE-890:
-------------------------------------

As part of MAPREDUCE-842, job directories are set to have the following permissions:

||        permissions        ||        user ownership        ||        group ownership        ||        file/dir name        ||
|        dr-xrws---               |        $job-owner                |        $tt_group                      |job_200908190916_0002|

CASE I: the $job-owner is other than the $tt_user
$tt_user is part of $tt_group, and so can create attempt directories inside the job directory as part of the task-localization because job_directory is group writable.

CASE II: the $job-owner is same as the $tt_user
TT cannot create attempt directories inside the job directory!! Because Linux seems to check uid of the process with the fsuid of the directory and return error if the directory is not user writable!

CASE II is what is causing the current bug.

Alternative solutions at hand:
 - Leave the code as is, and live with the fact that user's cannot submit jobs as mapred user
 - Set drwxrws--- on $job-dir in all cases. This means user's tasks CAN potentially create unwarranted files/dirs in the $job_dir
 - Set drwxrws-- if the $job-owner is same as the $tt_user, set  dr-xrws--- otherwise. Handles both the cases, but complicates code very slightly.

Thoughts?

> After HADOOP-4491, the user who started mapred system is not able to run job.
> -----------------------------------------------------------------------------
>
>                 Key: MAPREDUCE-890
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-890
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>          Components: tasktracker
>            Reporter: Karam Singh
>
> Even setup and cleanup task of job fails due exception -: It fails to create job and related directories under mapred.local.dir/taskTracker/jobcache
> Directories are created as -:
> [dr-xrws--- mapred   hadoop  ]  job_200908190916_0002
> mapred is not wrtie under this. Even manually I failed to touch file.
> mapred is use of started mr cluster 

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