[jira] [Created] (MAPREDUCE-5966) MR1 FairScheduler use of custom weight adjuster is not thread safe for comparisons

["Anubhav Dhoot (JIRA)" <ji...@apache.org>]

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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