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https://issues.apache.org/jira/browse/YARN-8373?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16975689#comment-16975689
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Wilfred Spiegelenburg commented on YARN-8373:
---------------------------------------------
I missed that in the {{PriorityQueue}}. Not really obvious that the iterator
does that. I have changed to a {{TreeSet}}.
I looked at that however the problem is that {{Collections.sort()}} uses
{{TimSort}} Which means that to use that we must be able to guarantee that
there is no way that the objects being sorted cannot change while sorting. The
node object that we sort are not locked while we are sorting. This means that
we cannot guarantee that. To guarantee no change we would need to lock all
individual nodes for the time we are sorting. A rather large performance impact.
On top of that even if in the current code path we do not have more than one
thread that changes the node there is no guarantee that behaviour will not
change. Since the {{ClusterNodeTracker}} is used by all scheduler we also
cannot guarantee that a different scheduler does not do it or uses the same
method.
Based on all that it is better to be defensive and use the TreeSet.
You can easily reproduce the issue with the unit test that has been updated.
When you use a {{Collection.sort()}} in the {{ClusterNodeTracker}} you will see
the test fail. At least it did for me every single time I ran it.
> RM Received RMFatalEvent of type CRITICAL_THREAD_CRASH
> -------------------------------------------------------
>
> Key: YARN-8373
> URL: https://issues.apache.org/jira/browse/YARN-8373
> Project: Hadoop YARN
> Issue Type: Bug
> Components: fairscheduler, resourcemanager
> Affects Versions: 2.9.0
> Reporter: Girish Bhat
> Assignee: Wilfred Spiegelenburg
> Priority: Major
> Labels: newbie
> Attachments: YARN-8373.001.patch, YARN-8373.002.patch,
> YARN-8373.003.patch, YARN-8373.004.patch
>
>
>
>
> {noformat}
> sudo -u yarn /usr/local/hadoop/latest/bin/yarn version Hadoop 2.9.0
> Subversion https://git-wip-us.apache.org/repos/asf/hadoop.git -r
> 756ebc8394e473ac25feac05fa493f6d612e6c50 Compiled by arsuresh on
> 2017-11-13T23:15Z Compiled with protoc 2.5.0 From source with checksum
> 0a76a9a32a5257331741f8d5932f183 This command was run using
> /usr/local/hadoop/hadoop-2.9.0/share/hadoop/common/hadoop-common-2.9.0.jar{noformat}
> This is for version 2.9.0
>
> {noformat}
> 2018-05-25 05:53:12,742 ERROR
> org.apache.hadoop.yarn.server.resourcemanager.ResourceManager: Received
> RMFatalEvent of type CRITICAL_THREAD_CRASH, caused by a critical thread, Fai
> rSchedulerContinuousScheduling, that exited unexpectedly:
> java.lang.IllegalArgumentException: Comparison method violates its general
> contract!
> at java.util.TimSort.mergeHi(TimSort.java:899)
> at java.util.TimSort.mergeAt(TimSort.java:516)
> at java.util.TimSort.mergeForceCollapse(TimSort.java:457)
> at java.util.TimSort.sort(TimSort.java:254)
> at java.util.Arrays.sort(Arrays.java:1512)
> at java.util.ArrayList.sort(ArrayList.java:1454)
> at java.util.Collections.sort(Collections.java:175)
> at
> org.apache.hadoop.yarn.server.resourcemanager.scheduler.ClusterNodeTracker.sortedNodeList(ClusterNodeTracker.java:340)
> at
> org.apache.hadoop.yarn.server.resourcemanager.scheduler.fair.FairScheduler.continuousSchedulingAttempt(FairScheduler.java:907)
> at
> org.apache.hadoop.yarn.server.resourcemanager.scheduler.fair.FairScheduler$ContinuousSchedulingThread.run(FairScheduler.java:296)
> 2018-05-25 05:53:12,743 FATAL
> org.apache.hadoop.yarn.server.resourcemanager.ResourceManager: Shutting down
> the resource manager.
> 2018-05-25 05:53:12,749 INFO org.apache.hadoop.util.ExitUtil: Exiting with
> status 1: a critical thread, FairSchedulerContinuousScheduling, that exited
> unexpectedly: java.lang.IllegalArgumentException: Comparison method violates
> its general contract!
> at java.util.TimSort.mergeHi(TimSort.java:899)
> at java.util.TimSort.mergeAt(TimSort.java:516)
> at java.util.TimSort.mergeForceCollapse(TimSort.java:457)
> at java.util.TimSort.sort(TimSort.java:254)
> at java.util.Arrays.sort(Arrays.java:1512)
> at java.util.ArrayList.sort(ArrayList.java:1454)
> at java.util.Collections.sort(Collections.java:175)
> at
> org.apache.hadoop.yarn.server.resourcemanager.scheduler.ClusterNodeTracker.sortedNodeList(ClusterNodeTracker.java:340)
> at
> org.apache.hadoop.yarn.server.resourcemanager.scheduler.fair.FairScheduler.continuousSchedulingAttempt(FairScheduler.java:907)
> at
> org.apache.hadoop.yarn.server.resourcemanager.scheduler.fair.FairScheduler$ContinuousSchedulingThread.run(FairScheduler.java:296)
> 2018-05-25 05:53:12,772 ERROR
> org.apache.hadoop.security.token.delegation.AbstractDelegationTokenSecretManager:
> ExpiredTokenRemover received java.lang.InterruptedException: sleep
> interrupted{noformat}
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