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https://issues.apache.org/jira/browse/YARN-3762?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14571502#comment-14571502
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Karthik Kambatla commented on YARN-3762:
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Thanks for the review, Arun. Good points.
bq. what happens if the collection is modified in between..
The two possible modifications are adding/removing a child queue. Adding a
child queue to the end of the list doesn't affect container assignment.
Removing a child queue affects container assignment, but that is a good thing.
We should probably add a comment to that effect so we don't forget this in the
future.
bq. instead of using a List and sorting it everytime, we could use a Sorted Bag
(MultiSet) ?
One issue with using a sorted list is the sorting happens on addition/removal.
FSQueues already in the list also change affecting the "order". May be, we
could remove and re-insert the queue if anything changes, but that is a much
bigger change and needs to be carefully evaluated for performance.
> FairScheduler: CME on FSParentQueue#getQueueUserAclInfo
> -------------------------------------------------------
>
> Key: YARN-3762
> URL: https://issues.apache.org/jira/browse/YARN-3762
> Project: Hadoop YARN
> Issue Type: Bug
> Components: fairscheduler
> Affects Versions: 2.7.0
> Reporter: Karthik Kambatla
> Assignee: Karthik Kambatla
> Priority: Critical
> Attachments: yarn-3762-1.patch, yarn-3762-1.patch
>
>
> In our testing, we ran into the following ConcurrentModificationException:
> {noformat}
> halxg.cloudera.com:8042, nodeRackName/rackvb07, nodeNumContainers0
> 15/05/22 13:02:22 INFO distributedshell.Client: Queue info,
> queueName=root.testyarnpool3, queueCurrentCapacity=0.0,
> queueMaxCapacity=-1.0, queueApplicationCount=0, queueChildQueueCount=0
> 15/05/22 13:02:22 FATAL distributedshell.Client: Error running Client
> java.util.ConcurrentModificationException:
> java.util.ConcurrentModificationException
> at java.util.ArrayList$Itr.checkForComodification(ArrayList.java:901)
> at java.util.ArrayList$Itr.next(ArrayList.java:851)
> at
> org.apache.hadoop.yarn.server.resourcemanager.scheduler.fair.FSParentQueue.getQueueUserAclInfo(FSParentQueue.java:155)
> at
> org.apache.hadoop.yarn.server.resourcemanager.scheduler.fair.FairScheduler.getQueueUserAclInfo(FairScheduler.java:1395)
> at
> org.apache.hadoop.yarn.server.resourcemanager.ClientRMService.getQueueUserAcls(ClientRMService.java:880)
> {noformat}
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