[YARN-1692] ConcurrentModificationException in fair scheduler AppSchedulable

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.0.5-alpha
• Fix Version/s: 2.4.0
• Component/s: scheduler
• Hadoop Flags: Reviewed
• Assignee: Sangjin Lee
• Reporter: Sangjin Lee
• Created: 07/Feb/14 02:01
• Updated: 10/Apr/14 13:11
• Resolved: 12/Feb/14 23:18

Description

We saw a ConcurrentModificationException thrown in the fair scheduler:

2014-02-07 01:40:01,978 ERROR org.apache.hadoop.yarn.server.resourcemanager.scheduler.fair.FairScheduler: Exception in fair scheduler UpdateThread
java.util.ConcurrentModificationException
        at java.util.HashMap$HashIterator.nextEntry(HashMap.java:926)
        at java.util.HashMap$ValueIterator.next(HashMap.java:954)
        at org.apache.hadoop.yarn.server.resourcemanager.scheduler.fair.AppSchedulable.updateDemand(AppSchedulable.java:85)
        at org.apache.hadoop.yarn.server.resourcemanager.scheduler.fair.FSLeafQueue.updateDemand(FSLeafQueue.java:125)
        at org.apache.hadoop.yarn.server.resourcemanager.scheduler.fair.FSParentQueue.updateDemand(FSParentQueue.java:82)
        at org.apache.hadoop.yarn.server.resourcemanager.scheduler.fair.FairScheduler.update(FairScheduler.java:217)
        at org.apache.hadoop.yarn.server.resourcemanager.scheduler.fair.FairScheduler$UpdateThread.run(FairScheduler.java:195)
        at java.lang.Thread.run(Thread.java:724)

The map that gets returned by FSSchedulerApp.getResourceRequests() are iterated on without proper synchronization.

Issue Links

• relates to: YARN-301 Fair scheduler throws ConcurrentModificationException when iterating over app's priorities