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From "Sandy Ryza (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (YARN-499) On container failure, include last n lines of logs in diagnostics
Date Wed, 27 Mar 2013 00:39:16 GMT

    [ https://issues.apache.org/jira/browse/YARN-499?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13614738#comment-13614738
] 

Sandy Ryza commented on YARN-499:
---------------------------------

Ravi,

The idea of putting the app master in a big try/catch seems good to me, but I was envisioning
this JIRA to encompass something more general that would handle non-AM container logs, containers
that OOM before getting into the main function, and containers that don't run java.  It's
true that the approach I outlined doesn't deterministically report exceptions, but it at least
gets us back to parity with MR1, and I believe that in most cases (and in all cases that I've
seen), the end of the log contains the helpful information.
                
> On container failure, include last n lines of logs in diagnostics
> -----------------------------------------------------------------
>
>                 Key: YARN-499
>                 URL: https://issues.apache.org/jira/browse/YARN-499
>             Project: Hadoop YARN
>          Issue Type: Improvement
>          Components: nodemanager
>    Affects Versions: 2.0.3-alpha
>            Reporter: Sandy Ryza
>            Assignee: Sandy Ryza
>
> When a container fails, the only way to diagnose it is to look at the logs.  ContainerStatuses
include a diagnostic string that is reported back to the resource manager by the node manager.
> Currently in MR2 I believe whatever is sent to the task's standard out is added to the
diagnostics string, but for MR standard out is redirected to a file called stdout.  In MR1,
this string was populated with the last few lines of the task's stdout file, and got printed
to the console, allowing for easy debugging.
> Handling this would help to soothe the infuriating problem of an AM dying for a mysterious
reason before setting a tracking URL (MAPREDUCE-3688).
> This could be done in one of two ways.
> * Use tee to send MR's standard out to both the stdout file and standard out.  This requires
modifying ShellCmdExecutor to roll what it reads in, as we wouldn't want to be storing the
entire task log in NM memory.
> * Read the task's log files.  This would require standardizing or making the container
log files configurable.  Right now the log files are determined in userland and all that is
YARN is aware of the log directory.
> Does this present any issues I'm not considering?  If so it this might only be needed
for AMs? 

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