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From "Thomas Graves (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (MAPREDUCE-4817) Hardcoded task ping timeout kills tasks localizing large amounts of data
Date Tue, 27 Nov 2012 17:19:58 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-4817?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13504777#comment-13504777

Thomas Graves commented on MAPREDUCE-4817:

When you say knock off the ping thread I assume you really mean just the ping timeout check
since the task progress happens in the same thread?

So the ping serves multiple purposes.  Currently it notifies the AM that the task has "pinged"
in and is still running.  This could be useful even with taskTimeout since the taskTimeout
could be turned off (set to 0) and we would never know if that task got hung.  Second, the
task uses it to check to see if the AM is still alive.  If it doesn't return true, the task
is supposed to exit.  1.X also had the ping check, but it went to the taskTracker and the
tasktracker validated that the parent Task of the ping checker thread was still there.

Now with 0.23 the nodemanager is watching the processes and talking back to the RM to let
it know that the AM died and if it died it kills the other tasks, but if the entire nodemanager
goes down then the task doesn't know the AM went away.  If the task isn't sending progress,
and the task timeout is set to 0, and this is the last AM retry it could hang around forever.

The odds of that seem pretty small and I guess if we aren't worried about the first happening,
the second probably isn't that interesting either. But we could also just remove the ping
timeout check in the TaskHeartBeatHandler.    What exactly are you proposing?
> Hardcoded task ping timeout kills tasks localizing large amounts of data
> ------------------------------------------------------------------------
>                 Key: MAPREDUCE-4817
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-4817
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>          Components: applicationmaster, mr-am
>    Affects Versions: 0.23.3, 2.0.3-alpha
>            Reporter: Jason Lowe
>            Assignee: Thomas Graves
>            Priority: Critical
> When a task is launched and spends more than 5 minutes localizing files, the AM will
kill the task due to ping timeout.  The AM's TaskHeartbeatHandler currently tracks tasks via
a progress timeout and a ping timeout.  The progress timeout can be controlled via mapreduce.task.timeout
and even disabled by setting the property to 0.  The ping timeout, however, is hardcoded to
5 minutes and cannot be configured.  Therefore if the task takes too long localizing, it never
gets running in order to ping back to the AM and the AM kills it due to ping timeout.

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