[SPARK-3032] Potential bug when running sort-based shuffle with sorting using TimSort

• Type: Bug
• Status: Resolved
• Priority: Blocker
• Resolution: Fixed
• Affects Version/s: 1.1.0
• Fix Version/s: 1.1.1, 1.2.0
• Component/s: Shuffle, Spark Core
• Target Version/s: 1.2.0
• Assignee: Saisai Shao
• Reporter: Saisai Shao
• Created: 14/Aug/14 07:56
• Updated: 17/May/20 18:30
• Resolved: 29/Sep/14 18:26

Description

When using SparkPerf's aggregate-by-key workload to test sort-based shuffle, data type for key and value is (String, String), always meet this issue:

java.lang.IllegalArgumentException: Comparison method violates its general contract!
        at org.apache.spark.util.collection.Sorter$SortState.mergeLo(Sorter.java:755)
        at org.apache.spark.util.collection.Sorter$SortState.mergeAt(Sorter.java:493)
        at org.apache.spark.util.collection.Sorter$SortState.mergeCollapse(Sorter.java:420)
        at org.apache.spark.util.collection.Sorter$SortState.access$200(Sorter.java:294)
        at org.apache.spark.util.collection.Sorter.sort(Sorter.java:128)
        at org.apache.spark.util.collection.SizeTrackingPairBuffer.destructiveSortedIterator(SizeTrackingPairBuffer.scala:83)
        at org.apache.spark.util.collection.ExternalSorter.spillToMergeableFile(ExternalSorter.scala:323)
        at org.apache.spark.util.collection.ExternalSorter.spill(ExternalSorter.scala:271)
        at org.apache.spark.util.collection.ExternalSorter.maybeSpill(ExternalSorter.scala:249)
        at org.apache.spark.util.collection.ExternalSorter.insertAll(ExternalSorter.scala:220)
        at org.apache.spark.shuffle.sort.SortShuffleWriter.write(SortShuffleWriter.scala:85)
        at org.apache.spark.scheduler.ShuffleMapTask.runTask(ShuffleMapTask.scala:68)
        at org.apache.spark.scheduler.ShuffleMapTask.runTask(ShuffleMapTask.scala:41)
        at org.apache.spark.scheduler.Task.run(Task.scala:54)
        at org.apache.spark.executor.Executor$TaskRunner.run(Executor.scala:199)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
        at java.lang.Thread.run(Thread.java:722)

Seems the current partitionKeyComparator which use hashcode of String as key comparator break some sorting contracts.

Also I tested using data type Int as key, this is OK to pass the test, since hashcode of Int is its self. So I think potentially partitionDiff + hashcode of String may break the sorting contracts.

Issue Links

• is duplicated by: SPARK-3656 IllegalArgumentException when I using sort-based shuffle
• links to: [Github] Pull Request #2514 (jerryshao)