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From "Ahmed Radwan (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (MAPREDUCE-3728) ShuffleHandler can't access results when configured in a secure mode
Date Wed, 29 Feb 2012 19:51:59 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-3728?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13219461#comment-13219461

Ahmed Radwan commented on MAPREDUCE-3728:

As I mentioned earlier, it seems that the problem is mainly on how the output directory is
created in ContainerLocalizer.java. The setgid is lost in the process. I have even tried to
set the permissions explicitly and setting setgid but also this doesn't seem to solve the

So I think the current patch, where the output directory creation is postponed is appropriate
as it is correctly created afterwards by FileSystem.create(). We may also need to investigate
more why mkdir in AbstractFileSystem in this case is causing the loss of setgid, and see if
this a bug or it is an intentional behavior.
> ShuffleHandler can't access results when configured in a secure mode
> --------------------------------------------------------------------
>                 Key: MAPREDUCE-3728
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-3728
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>          Components: mrv2, nodemanager
>    Affects Versions: 0.23.0
>            Reporter: Roman Shaposhnik
>            Assignee: Ahmed Radwan
>            Priority: Critical
>             Fix For: 0.23.1
>         Attachments: MAPREDUCE-3728.patch
> While running the simplest of jobs (Pi) on MR2 in a fully secure configuration I have
noticed that the job was failing on the reduce side with the following messages littering
the nodemanager logs:
> {noformat}
> 2012-01-19 08:35:32,544 ERROR org.apache.hadoop.mapred.ShuffleHandler: Shuffle error
> org.apache.hadoop.util.DiskChecker$DiskErrorException: Could not find usercache/rvs/appcache/application_1326928483038_0001/output/attempt_1326928483038_0001_m_000003_0/file.out.index
in any of the configured local directories
> {noformat}
> While digging further I found out that the permissions on the files/dirs were prohibiting
nodemanager (running under the user yarn) to access these files:
> {noformat}
> $ ls -l /data/3/yarn/usercache/testuser/appcache/application_1327102703969_0001/output/attempt_1327102703969_0001_m_000001_0
> -rw-r----- 1 testuser testuser 28 Jan 20 15:41 file.out
> -rw-r----- 1 testuser testuser 32 Jan 20 15:41 file.out.index
> {noformat}
> Digging even further revealed that the group-sticky bit that was faithfully put on all
the subdirectories between testuser and application_1327102703969_0001 was gone from output
and attempt_1327102703969_0001_m_000001_0. 
> Looking into how these subdirectories are created (org.apache.hadoop.yarn.server.nodemanager.containermanager.localizer.ContainerLocalizer.initDirs())
> {noformat}
>       // $x/usercache/$user/appcache/$appId/filecache
>       Path appFileCacheDir = new Path(appBase, FILECACHE);
>       appsFileCacheDirs[i] = appFileCacheDir.toString();
>       lfs.mkdir(appFileCacheDir, null, false);
>       // $x/usercache/$user/appcache/$appId/output
>       lfs.mkdir(new Path(appBase, OUTPUTDIR), null, false);
> {noformat}
> Reveals that lfs.mkdir ends up manipulating permissions and thus clears sticky bit from
output and filecache.
> At this point I'm at a loss about how this is supposed to work. My understanding was
> that the whole sequence of events here was predicated on a sticky bit set so
> that daemons running under the user yarn (default group yarn) can have access
> to the resulting files and subdirectories down at output and below. Please let
> me know if I'm missing something or whether this is just a bug that needs to be fixed.
> On a related note, when the shuffle side of the Pi job failed the job itself didn't.
> It went into the endless loop and only exited when it exhausted all the local storage
> for the log files (at which point the nodemanager died and thus the job ended). Perhaps
> this is even more serious side effect of this issue that needs to be investigated 
> separately.

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