Details
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Bug
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Status: Closed
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Major
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Resolution: Fixed
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2.5.0, 2.6.0, 2.5.1, 2.5.2
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
