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https://issues.apache.org/jira/browse/YARN-3508?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14606576#comment-14606576
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Wangda Tan commented on YARN-3508:
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[~varun_saxena],
It seems to me this patch doesn't work as what I expected:
I think we PreemptionPolicy should directly send events to scheduler event
dispatcher, so events won't go to rmDispatcher. What [~jlowe]/[~jianhe]
suggested should be the same.
Now my understanding of this patch is, preemption events still go to
rmDispatcher, and rmDispatcher sends events to schedulerDispatcher:
{code}
@SuppressWarnings("unchecked")
public void serviceInit(Configuration conf) throws Exception {
scheduleEditPolicy.init(conf, rmContext.getDispatcher().getEventHandler(),
(PreemptableResourceScheduler) rmContext.getScheduler());
this.monitorInterval = scheduleEditPolicy.getMonitoringInterval();
super.serviceInit(conf);
}
{code}
I think one solution is exposing scheduler events dispatcher to RMContext
interface, so schedulerEditPolicy can use the schedulerDispatcher do
initialization.
And could you take a look at failed tests, it looks like related to the patch.
> Preemption processing occuring on the main RM dispatcher
> --------------------------------------------------------
>
> Key: YARN-3508
> URL: https://issues.apache.org/jira/browse/YARN-3508
> Project: Hadoop YARN
> Issue Type: Bug
> Components: resourcemanager, scheduler
> Affects Versions: 2.6.0
> Reporter: Jason Lowe
> Assignee: Varun Saxena
> Attachments: YARN-3508.002.patch, YARN-3508.01.patch,
> YARN-3508.03.patch, YARN-3508.04.patch
>
>
> We recently saw the RM for a large cluster lag far behind on the
> AsyncDispacher event queue. The AsyncDispatcher thread was consistently
> blocked on the highly-contended CapacityScheduler lock trying to dispatch
> preemption-related events for RMContainerPreemptEventDispatcher. Preemption
> processing should occur on the scheduler event dispatcher thread or a
> separate thread to avoid delaying the processing of other events in the
> primary dispatcher queue.
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