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https://issues.apache.org/jira/browse/YARN-9195?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16770479#comment-16770479
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Weiwei Yang commented on YARN-9195:
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Sure [~leftnoteasy], I'll help to review this. Sorry for late response, I was
occupied on something else last week.
Thanks [~ssy] for filing the issue. Just read the patch, I am trying to
understand {{refreshContainersFromPreviousAttempts()}}, if a container from
previous attempt is completed, then you are not removing it from outstanding
requests. Why are you doing this?
I am also not sure why you need to \{{initApplicationAttempt()}}, this is
retrieving current app attempt id from AM RM token. Since in the protocol, we
have \{{getContainersFromPreviousAttempts()}} already, what's the attempt id is
used for here?
Thanks
> RM Queue's pending container number might get decreased unexpectedly or even
> become negative once RM failover
> -------------------------------------------------------------------------------------------------------------
>
> Key: YARN-9195
> URL: https://issues.apache.org/jira/browse/YARN-9195
> Project: Hadoop YARN
> Issue Type: Bug
> Components: client
> Affects Versions: 3.1.0
> Reporter: Shengyang Sha
> Assignee: Shengyang Sha
> Priority: Critical
> Attachments: YARN-9195.001.patch, YARN-9195.002.patch,
> cases_to_recreate_negative_pending_requests_scenario.diff
>
>
> Hi, all:
> Previously we have encountered a serious problem in ResourceManager, we found
> that pending container number of one RM queue became negative after RM failed
> over. Since queues in RM are managed in hierarchical structure, the root
> queue's pending containers became negative at last, thus the scheduling
> process of the whole cluster became affected.
> The version of both our RM server and AMRM client in our application are
> based on yarn 3.1, and we uses AMRMClientAsync#addSchedulingRequests() method
> in our application to request resources from RM.
> After investigation, we found that the direct cause was numAllocations of
> some AMs' requests became negative after RM failed over. And there are at
> lease three necessary conditions:
> (1) Use schedulingRequests in AMRM client, and the application set zero to
> the numAllocations for a schedulingRequest. In our batch job scenario, the
> numAllocations of a schedulingRequest could turn to zero because
> theoretically we can run a full batch job using only one container.
> (2) RM failovers.
> (3) Before AM reregisters itself to RM after RM restarts, RM has already
> recovered some of the application's containers assigned before.
> Here are some more details about the implementation:
> (1) After RM recovers, RM will send all alive containers to AM once it
> re-register itself through
> RegisterApplicationMasterResponse#getContainersFromPreviousAttempts.
> (2) During registerApplicationMaster, AMRMClientImpl will
> removeFromOutstandingSchedulingRequests once AM gets
> ContainersFromPreviousAttempts without checking whether these containers have
> been assigned before. As a consequence, its outstanding requests might be
> decreased unexpectedly even if it may not become negative.
> (3) There is no sanity check in RM to validate requests from AMs.
> For better illustrating this case, I've written a test case based on the
> latest hadoop trunk, posted in the attachment. You may try case
> testAMRMClientWithNegativePendingRequestsOnRMRestart and
> testAMRMClientOnUnexpectedlyDecreasedPendingRequestsOnRMRestart .
> To solve this issue, I propose to filter allocated containers before
> removeFromOutstandingSchedulingRequests in AMRMClientImpl during
> registerApplicationMaster, and some sanity checks are also needed to prevent
> things from getting worse.
> More comments and suggestions are welcomed.
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