Anubhav Dhoot created MAPREDUCE-5966:
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Summary: MR1 FairScheduler use of custom weight adjuster is not
thread safe for comparisons
Key: MAPREDUCE-5966
URL: https://issues.apache.org/jira/browse/MAPREDUCE-5966
Project: Hadoop Map/Reduce
Issue Type: Bug
Reporter: Anubhav Dhoot
When comparing JobSchedulables one of the factors is the weight. If someone
uses a custom weight adjuster, that may be called multiple times during a sort
causing different values to return. That causes a failure in sorting because
the weight may change during the sort.
This reproes as
{code}
java.io.IOException: java.lang.IllegalArgumentException: Comparison method
violates its general contract!
at java.util.TimSort.mergeHi(TimSort.java:868)
at java.util.TimSort.mergeAt(TimSort.java:485)
at java.util.TimSort.mergeCollapse(TimSort.java:410)
at java.util.TimSort.sort(TimSort.java:214)
at java.util.TimSort.sort(TimSort.java:173)
at java.util.Arrays.sort(Arrays.java:659)
at java.util.Collections.sort(Collections.java:217)
at org.apache.hadoop.mapred.PoolSchedulable.assignTask(PoolSchedulable.java:163)
at org.apache.hadoop.mapred.FairScheduler.assignTasks(FairScheduler.java:499)
at org.apache.hadoop.mapred.JobTracker.heartbeat(JobTracker.java:2961)
{code}
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