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From "Jian He (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (YARN-6959) RM may allocate wrong AM Container for new attempt
Date Tue, 08 Aug 2017 18:40:00 GMT

    [ https://issues.apache.org/jira/browse/YARN-6959?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16118836#comment-16118836

Jian He commented on YARN-6959:

[~yqwang], thanks for the patch. one question is I'm wondering under what scenario this can
happen. For each failed attempt, we remove it from the ApplicationMasterService#responseMap,
 and in ApplicationMasterService#allocate we will check is the attempt is in the responseMap,
if not, that will block allocate into scheduler.
Do you see this log line in ApplicationMasterService for the 1st attempt ?
{{LOG.info("Unregistering app attempt : " + attemptId);}}

> RM may allocate wrong AM Container for new attempt
> --------------------------------------------------
>                 Key: YARN-6959
>                 URL: https://issues.apache.org/jira/browse/YARN-6959
>             Project: Hadoop YARN
>          Issue Type: Bug
>          Components: capacity scheduler, fairscheduler, scheduler
>    Affects Versions: 2.7.1
>            Reporter: Yuqi Wang
>            Assignee: Yuqi Wang
>              Labels: patch
>             Fix For: 2.7.1, 3.0.0-alpha4
>         Attachments: YARN-6959.001.patch, YARN-6959.002.patch, YARN-6959.003.patch, YARN-6959.004.patch,
YARN-6959.005.patch, YARN-6959-branch-2.7.001.patch
> *Issue Summary:*
> Previous attempt ResourceRequest may be recorded into current attempt ResourceRequests.
These mis-recorded ResourceRequests may confuse AM Container Request and Allocation for current
> *Issue Pipeline:*
> {code:java}
> // Executing precondition check for the incoming attempt id.
> ApplicationMasterService.allocate() ->
> scheduler.allocate(attemptId, ask, ...) ->
> // Previous precondition check for the attempt id may be outdated here, 
> // i.e. the currentAttempt may not be the corresponding attempt of the attemptId.
> // Such as the attempt id is corresponding to the previous attempt.
> currentAttempt = scheduler.getApplicationAttempt(attemptId) ->
> // Previous attempt ResourceRequest may be recorded into current attempt ResourceRequests
> currentAttempt.updateResourceRequests(ask) ->
> // RM may allocate wrong AM Container for the current attempt, because its ResourceRequests
> // may come from previous attempt which can be any ResourceRequests previous AM asked
> // and there is not matching logic for the original AM Container ResourceRequest and

> // the returned amContainerAllocation below.
> AMContainerAllocatedTransition.transition(...) ->
> amContainerAllocation = scheduler.allocate(currentAttemptId, ...)
> {code}
> *Patch Correctness:*
> Because after this Patch, RM will definitely record ResourceRequests from different attempt
into different objects of SchedulerApplicationAttempt.AppSchedulingInfo.
> So, even if RM still record ResourceRequests from old attempt at any time, these ResourceRequests
will be recorded in old AppSchedulingInfo object which will not impact current attempt's resource
requests and allocation.
> *Concerns:*
> The getApplicationAttempt function in AbstractYarnScheduler is so confusing, we should
better rename it to getCurrentApplicationAttempt. And reconsider whether there are any other
bugs related to getApplicationAttempt.

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