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https://issues.apache.org/jira/browse/YARN-10283?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17126128#comment-17126128
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Jim Brennan commented on YARN-10283:
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Thanks [~epayne]. Just to be clear, you are referring to the patch for
YARN-9903?
> Capacity Scheduler: starvation occurs if a higher priority queue is full and
> node labels are used
> -------------------------------------------------------------------------------------------------
>
> Key: YARN-10283
> URL: https://issues.apache.org/jira/browse/YARN-10283
> Project: Hadoop YARN
> Issue Type: Bug
> Components: capacity scheduler
> Reporter: Peter Bacsko
> Assignee: Peter Bacsko
> Priority: Major
> Attachments: YARN-10283-POC01.patch, YARN-10283-ReproTest.patch,
> YARN-10283-ReproTest2.patch
>
>
> Recently we've been investigating a scenario where applications submitted to
> a lower priority queue could not get scheduled because a higher priority
> queue in the same hierarchy could now satisfy the allocation request. Both
> queue belonged to the same partition.
> If we disabled node labels, the problem disappeared.
> The problem is that {{RegularContainerAllocator}} always allocated a
> container for the request, even if it should not have.
> *Example:*
> * Cluster total resources: 3 nodes, 15GB, 24 vcores (5GB / 8 vcore per node)
> * Partition "shared" was created with 2 nodes
> * "root.lowprio" (priority = 20) and "root.highprio" (priorty = 40) were
> added to the partition
> * Both queues have a limit of <memory:5120, vCores:8>
> * Using DominantResourceCalculator
> Setup:
> Submit distributed shell application to highprio with switches
> "-num_containers 3 -container_vcores 4". The memory allocation is 512MB per
> container.
> Chain of events:
> 1. Queue is filled with contaners until it reaches usage <memory:2560,
> vCores:5>
> 2. A node update event is pushed to CS from a node which is part of the
> partition
> 2. {{AbstractCSQueue.canAssignToQueue()}} returns true because it's smaller
> than the current limit resource <memory:5120, vCores:8>
> 3. Then {{LeafQueue.assignContainers()}} runs successfully and gets an
> allocated container for <memory:512, vcores:4>
> 4. But we can't commit the resource request because we would have 9 vcores in
> total, violating the limit.
> The problem is that we always try to assign container for the same
> application in each heartbeat from "highprio". Applications in "lowprio"
> cannot make progress.
> *Problem:*
> {{RegularContainerAllocator.assignContainer()}} does not handle this case
> well. We only reject allocation if this condition is satisfied:
> {noformat}
> if (rmContainer == null && reservationsContinueLooking
> && node.getLabels().isEmpty()) {
> {noformat}
> But if we have node labels, we enter a different code path and succeed with
> the allocation if there's room for a container.
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