[HDFS-10396] Using -diff option with DistCp may get "Comparison method violates its general contract" exception

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 2.7.4
• Hadoop Flags: Reviewed
• Assignee: Yongjun Zhang
• Reporter: Yongjun Zhang
• Created: 12/May/16 21:56
• Updated: 29/Jun/16 07:09
• Resolved: 29/Jun/16 07:09

Description

Using -diff option get the following exception due to a bug in the comparison operator:

16/04/21 14:34:18 WARN tools.DistCp: Failed to use snapshot diff for distcp
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.mergeForceCollapse(TimSort.java:426)
	at java.util.TimSort.sort(TimSort.java:223)
	at java.util.TimSort.sort(TimSort.java:173)
	at java.util.Arrays.sort(Arrays.java:659)
	at org.apache.hadoop.tools.DistCpSync.moveToTarget(DistCpSync.java:293)
	at org.apache.hadoop.tools.DistCpSync.syncDiff(DistCpSync.java:261)
	at org.apache.hadoop.tools.DistCpSync.sync(DistCpSync.java:131)
	at org.apache.hadoop.tools.DistCp.execute(DistCp.java:163)
	at org.apache.hadoop.tools.DistCp.run(DistCp.java:122)
	at org.apache.hadoop.util.ToolRunner.run(ToolRunner.java:70)
	at org.apache.hadoop.tools.DistCp.main(DistCp.java:432)
16/04/21 14:34:18 ERROR tools.DistCp: Exception encountered