[YARN-2910] FSLeafQueue can throw ConcurrentModificationException

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.5.0, 2.6.0, 2.5.1, 2.5.2
• Fix Version/s: 2.7.0, 2.6.1, 3.0.0-alpha1
• Component/s: fairscheduler
• Labels: 2.6.1-candidate
• Target Version/s: 2.7.0, 2.6.1
• Hadoop Flags: Reviewed
• Assignee: Wilfred Spiegelenburg
• Reporter: Wilfred Spiegelenburg
• Created: 27/Nov/14 06:19
• Updated: 26/Feb/20 05:29
• Resolved: 09/Dec/14 22:05

Description

The list that maintains the runnable and the non runnable apps are a standard ArrayList but there is no guarantee that it will only be manipulated by one thread in the system. This can lead to the following exception:

2014-11-12 02:29:01,169 ERROR [RMCommunicator Allocator] org.apache.hadoop.mapreduce.v2.app.rm.RMContainerAllocator: ERROR IN CONTACTING RM.
java.util.ConcurrentModificationException: java.util.ConcurrentModificationException
at java.util.ArrayList$Itr.checkForComodification(ArrayList.java:859)
at java.util.ArrayList$Itr.next(ArrayList.java:831)
at org.apache.hadoop.yarn.server.resourcemanager.scheduler.fair.FSLeafQueue.getResourceUsage(FSLeafQueue.java:147)
at org.apache.hadoop.yarn.server.resourcemanager.scheduler.fair.FSAppAttempt.getHeadroom(FSAppAttempt.java:180)
at org.apache.hadoop.yarn.server.resourcemanager.scheduler.fair.FairScheduler.allocate(FairScheduler.java:923)
at org.apache.hadoop.yarn.server.resourcemanager.ApplicationMasterService.allocate(ApplicationMasterService.java:516)

Full stack trace in the attached file.

We should guard against that by using a thread safe version from java.util.concurrent.CopyOnWriteArrayList

Issue Links

• relates to: YARN-2975 FSLeafQueue app lists are accessed without required locks
• relates to: YARN-2922 ConcurrentModificationException in CapacityScheduler's LeafQueue