[MAPREDUCE-1089] Fair Scheduler preemption triggers NPE when tasks are scheduled but not running

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.21.0
• Fix Version/s: 0.21.0
• Component/s: contrib/fair-share
• Hadoop Flags: Reviewed
• Assignee: Todd Lipcon Assign to me
• Reporter: Todd Lipcon
• Created: 10/Oct/09 00:55
• Updated: 24/Aug/10 21:18
• Resolved: 29/Oct/09 01:32

Description

We see exceptions like this when preemption runs when a task has been scheduled on a TT but has not yet started running.

2009-10-09 14:30:53,989 INFO org.apache.hadoop.mapred.FairScheduler: Should preempt 2 MAP tasks for job_200910091420_0006: tasksDueToMinShare = 2, tasksDueToFairShare = 0
2009-10-09 14:30:54,036 ERROR org.apache.hadoop.mapred.FairScheduler: Exception in fair scheduler UpdateThread
java.lang.NullPointerException
at org.apache.hadoop.mapred.FairScheduler$2.compare(FairScheduler.java:1015)
at org.apache.hadoop.mapred.FairScheduler$2.compare(FairScheduler.java:1013)
at java.util.Arrays.mergeSort(Arrays.java:1270)
at java.util.Arrays.sort(Arrays.java:1210)
at java.util.Collections.sort(Collections.java:159)
at org.apache.hadoop.mapred.FairScheduler.preemptTasks(FairScheduler.java:1013)
at org.apache.hadoop.mapred.FairScheduler.preemptTasksIfNecessary(FairScheduler.java:911)
at org.apache.hadoop.mapred.FairScheduler$UpdateThread.run(FairScheduler.java:286)