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https://issues.apache.org/jira/browse/YARN-7051?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16141684#comment-16141684
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Eric Payne commented on YARN-7051:
----------------------------------
Unit test failures are not related to this patch.
- {{TestContainerAllocation}}: YARN-7044
- {{h.y.s.r.security.TestDelegationTokenRenewer}}: YARN-5816
{code:title=LeafQueue#getAllApplications}
public Collection<FiCaSchedulerApp> getAllApplications() {
Collection<FiCaSchedulerApp> apps = new HashSet<FiCaSchedulerApp>(
pendingOrderingPolicy.getSchedulableEntities());
apps.addAll(orderingPolicy.getSchedulableEntities());
return Collections.unmodifiableCollection(apps);
}
{code}
bq. {{getAllApplications}} in {{LeafQueue}} then has to be under readlock also,
correct?
Possibly. It looks like {{HashSet#addAll}} will iterate through
{{orderingPolicy}}, which could possibly change during the loop. However, I
would like to have that discussion on a separate JIRA since I may be
misinterpreting how {{addAll}} works and since the usage of
{{getAAllApplications}} affects more than just preemption.
> FifoIntraQueuePreemptionPlugin can get concurrent modification exception
> ------------------------------------------------------------------------
>
> Key: YARN-7051
> URL: https://issues.apache.org/jira/browse/YARN-7051
> Project: Hadoop YARN
> Issue Type: Bug
> Components: capacity scheduler, scheduler preemption, yarn
> Affects Versions: 2.9.0, 2.8.1, 3.0.0-alpha3
> Reporter: Eric Payne
> Assignee: Eric Payne
> Priority: Critical
> Attachments: YARN-7051.001.patch, YARN-7051.002.patch
>
>
> {{FifoIntraQueuePreemptionPlugin#calculateUsedAMResourcesPerQueue}} has the
> following code:
> {code}
> Collection<FiCaSchedulerApp> runningApps = leafQueue.getApplications();
> Resource amUsed = Resources.createResource(0, 0);
> for (FiCaSchedulerApp app : runningApps) {
> {code}
> {{runningApps}} is unmodifiable but not concurrent. This caused the
> preemption monitor thread to crash in the RM in one of our clusters.
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