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From "Zhijie Shen (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (YARN-611) Add an AM retry count reset window to YARN RM
Date Thu, 04 Sep 2014 01:25:53 GMT

    [ https://issues.apache.org/jira/browse/YARN-611?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14120806#comment-14120806
] 

Zhijie Shen commented on YARN-611:
----------------------------------

[~xgong], the new patch looks good to me overall. I've just minor comments about the patch
details.

1. failure account -> failure count?
{code}
+ *     when slidingWindowSize is set to > 0, the failure number will no take
+ *     failures which happen out of the window into failure account.
+ *     If failure account reaches to maxAppAttempts,
{code}

2. Make get/setSlidingWindowSize description more consistent?

3. EndTime -> FinishTime? The latter term seems to be more commonly used in YARN.

4. end_time violates the code convention.
{code}
+      long end_time = attempts.get(attemptIds.get(0)).getEndTime();
{code}

5. I think sort is not necessary. We can simply iterator over each attempt and check whether
it should be take into account. The best sort is O(nlogn), though it doesn't make much difference,
because there won't be too many attempts. Anyway, I think the additional sorting work seems
not to be required.
{code}
+      Collections.sort(attemptIds, Collections.reverseOrder());
{code}

6. Why not using System.currentTimeMillis()?
{code}
+    setEndTime(Time.now());
{code}

7. In the test case, would you please add one more scenario: 2 failures within 6s will not
restart the 3rd attempt.

> 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: Sub-task
>          Components: resourcemanager
>    Affects Versions: 2.0.3-alpha
>            Reporter: Chris Riccomini
>            Assignee: Xuan Gong
>         Attachments: YARN-611.1.patch, YARN-611.2.patch, YARN-611.3.patch, YARN-611.4.patch,
YARN-611.4.rebase.patch, YARN-611.5.patch, YARN-611.6.patch
>
>
> 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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