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From "Chris Riccomini (JIRA)" <j...@apache.org>
Subject [jira] [Created] (YARN-611) Add an AM retry count reset window to YARN RM
Date Thu, 25 Apr 2013 18:28:18 GMT
Chris Riccomini created YARN-611:
------------------------------------

             Summary: Add an AM retry count reset window to YARN RM
                 Key: YARN-611
                 URL: https://issues.apache.org/jira/browse/YARN-611
             Project: Hadoop YARN
          Issue Type: Bug
          Components: resourcemanager
    Affects Versions: 2.0.3-alpha
            Reporter: Chris Riccomini


YARN currently has the following config:

yarn.resourcemanager.am.max-retries

This config defaults to 2, and defines how many times to retry a "failed" AM before failing
the whole YARN job. YARN counts an AM as failed if the node that it was running on dies (the
NM will timeout, which counts as a failure for the AM), or if the AM dies.

This configuration is insufficient for long running (or infinitely running) YARN jobs, since
the machine (or NM) that the AM is running on will eventually need to be restarted (or the
machine/NM will fail). In such an event, the AM has not done anything wrong, but this is counted
as a "failure" by the RM. Since the retry count for the AM is never reset, eventually, at
some point, the number of machine/NM failures will result in the AM failure count going above
the configured value for yarn.resourcemanager.am.max-retries. Once this happens, the RM will
mark the job as failed, and shut it down. This behavior is not ideal.

I propose that we add a second configuration:

yarn.resourcemanager.am.retry-count-window-ms

This configuration would define a window of time that would define when an AM is "well behaved",
and it's safe to reset its failure count back to zero. Every time an AM fails the RmAppImpl
would check the last time that the AM failed. If the last failure was less than retry-count-window-ms
ago, and the new failure count is > max-retries, then the job should fail. If the AM has
never failed, the retry count is < max-retries, or if the last failure was OUTSIDE the
retry-count-window-ms, then the job should be restarted. Additionally, if the last failure
was outside the retry-count-window-ms, then the failure count should be set back to 0.

This would give developers a way to have well-behaved AMs run forever, while still failing
mis-behaving AMs after a short period of time.

I think the work to be done here is to change the RmAppImpl to actually look at app.attempts,
and see if there have been more than max-retries failures in the last retry-count-window-ms
milliseconds. If there have, then the job should fail, if not, then the job should go forward.
Additionally, we might also need to add an endTime in either RMAppAttemptImpl or RMAppFailedAttemptEvent,
so that the RmAppImpl can check the time of the failure.

Thoughts?

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