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From "Tao Yang (JIRA)" <j...@apache.org>
Subject [jira] [Created] (YARN-9432) Excess reserved containers may exist for a long time after its request has been cancelled or satisfied when multi-nodes enabled
Date Mon, 01 Apr 2019 08:02:00 GMT
Tao Yang created YARN-9432:
------------------------------

             Summary: Excess reserved containers may exist for a long time after its request
has been cancelled or satisfied when multi-nodes enabled
                 Key: YARN-9432
                 URL: https://issues.apache.org/jira/browse/YARN-9432
             Project: Hadoop YARN
          Issue Type: Bug
          Components: capacityscheduler
            Reporter: Tao Yang
            Assignee: Tao Yang


Reserved containers may change to be excess after its request has been cancelled or satisfied,
excess reserved containers need to be unreserved quickly to release resource for others.

For multi-nodes disabled scenario, excess reserved containers can be quickly released in
next node heartbeat, the calling stack is CapacityScheduler#nodeUpdate -->  CapacityScheduler#allocateContainersToNode
--> CapacityScheduler#allocateContainerOnSingleNode. 

But for multi-nodes enabled scenario, excess reserved containers have chance to be released
only in allocation process, key phase of the calling stack is LeafQueue#assignContainers
--> LeafQueue#allocateFromReservedContainer. According to this, excess reserved containers
may not be released until its queue has pending request and has chance to be allocated, and
the worst is that excess reserved containers will never be released and keep holding resource
if there is no additional pending request for this queue.

To solve this problem, my opinion is to directly kill excess reserved containers when request
is satisfied (in FiCaSchedulerApp#apply) or the allocation number of resource-requests/scheduling-requests
is updated to be 0 (in SchedulerApplicationAttempt#updateResourceRequests / SchedulerApplicationAttempt#updateSchedulingRequests).

Please feel free to give your suggestions. Thanks.



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