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https://issues.apache.org/jira/browse/YARN-4743?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15173146#comment-15173146
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Zephyr Guo commented on YARN-4743:
----------------------------------
{quote}
I think that DRF comparator is not transitive with my intuition.
{quote}
I think that's right.[~ozawa]
FairShareComparator uses {{getResourceUsage()}} and {{getDemand()}} and
{{getMinShare()}} to implement {{compare(Schedulable s1, Schedulable s1)}}.The
three methods must return same Resource anyway while we are sorting, otherwise
will break transitivity.
How about add snapshot feature in Schedulable? We snapshot Schedulable before
sorting.Then we sort but use snapshot Resource in comparator . Result of
sorting will very close to real situation, because sorting is very fast.
> ResourceManager crash because TimSort
> -------------------------------------
>
> Key: YARN-4743
> URL: https://issues.apache.org/jira/browse/YARN-4743
> Project: Hadoop YARN
> Issue Type: Bug
> Components: fairscheduler
> Affects Versions: 2.6.4
> Reporter: Zephyr Guo
>
> {code}
> 2016-02-26 14:08:50,821 FATAL
> org.apache.hadoop.yarn.server.resourcemanager.ResourceManager: Error in
> handling event type NODE_UPDATE to the scheduler
> java.lang.IllegalArgumentException: Comparison method violates its general
> contract!
> at java.util.TimSort.mergeHi(TimSort.java:868)
> at java.util.TimSort.mergeAt(TimSort.java:485)
> at java.util.TimSort.mergeCollapse(TimSort.java:410)
> at java.util.TimSort.sort(TimSort.java:214)
> at java.util.TimSort.sort(TimSort.java:173)
> at java.util.Arrays.sort(Arrays.java:659)
> at java.util.Collections.sort(Collections.java:217)
> at
> org.apache.hadoop.yarn.server.resourcemanager.scheduler.fair.FSLeafQueue.assignContainer(FSLeafQueue.java:316)
> at
> org.apache.hadoop.yarn.server.resourcemanager.scheduler.fair.FSParentQueue.assignContainer(FSParentQueue.java:240)
> at
> org.apache.hadoop.yarn.server.resourcemanager.scheduler.fair.FairScheduler.attemptScheduling(FairScheduler.java:1091)
> at
> org.apache.hadoop.yarn.server.resourcemanager.scheduler.fair.FairScheduler.nodeUpdate(FairScheduler.java:989)
> at
> org.apache.hadoop.yarn.server.resourcemanager.scheduler.fair.FairScheduler.handle(FairScheduler.java:1185)
> at
> org.apache.hadoop.yarn.server.resourcemanager.scheduler.fair.FairScheduler.handle(FairScheduler.java:112)
> at
> org.apache.hadoop.yarn.server.resourcemanager.ResourceManager$SchedulerEventDispatcher$EventProcessor.run(ResourceManager.java:684)
> at java.lang.Thread.run(Thread.java:745)
> 2016-02-26 14:08:50,822 INFO
> org.apache.hadoop.yarn.server.resourcemanager.ResourceManager: Exiting, bbye..
> {code}
> Actually, this issue found in 2.6.0-cdh5.4.7.
> I think the cause is that we modify {{Resouce}} while we are sorting
> {{runnableApps}}.
> {code:title=FSLeafQueue.java}
> Comparator<Schedulable> comparator = policy.getComparator();
> writeLock.lock();
> try {
> Collections.sort(runnableApps, comparator);
> } finally {
> writeLock.unlock();
> }
> readLock.lock();
> {code}
> {code:title=FairShareComparator}
> public int compare(Schedulable s1, Schedulable s2) {
> ......
> s1.getResourceUsage(), minShare1);
> boolean s2Needy = Resources.lessThan(RESOURCE_CALCULATOR, null,
> s2.getResourceUsage(), minShare2);
> minShareRatio1 = (double) s1.getResourceUsage().getMemory()
> / Resources.max(RESOURCE_CALCULATOR, null, minShare1,
> ONE).getMemory();
> minShareRatio2 = (double) s2.getResourceUsage().getMemory()
> / Resources.max(RESOURCE_CALCULATOR, null, minShare2,
> ONE).getMemory();
> ......
> {code}
> {{getResourceUsage}} will return current Resource. The current Resource is
> unstable.
> {code:title=FSAppAttempt.java}
> @Override
> public Resource getResourceUsage() {
> // Here the getPreemptedResources() always return zero, except in
> // a preemption round
> return Resources.subtract(getCurrentConsumption(),
> getPreemptedResources());
> }
> {code}
> {code:title=SchedulerApplicationAttempt}
> public Resource getCurrentConsumption() {
> return currentConsumption;
> }
> // This method may modify current Resource.
> public synchronized void recoverContainer(RMContainer rmContainer) {
> ......
> Resources.addTo(currentConsumption, rmContainer.getContainer()
> .getResource());
> ......
> }
> {code}
> I suggest that use stable Resource in comparator.
> Is there something i think wrong？
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