[MAPREDUCE-1305] Running distcp with -delete incurs avoidable penalties

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.20.1
• Fix Version/s: 0.21.0
• Component/s: distcp
• Hadoop Flags: Reviewed
• Assignee: Peter Romianowski
• Reporter: Peter Romianowski
• Created: 16/Dec/09 22:32
• Updated: 24/Aug/10 21:19
• Resolved: 13/Feb/10 10:11

Description

First problem

In org.apache.hadoop.tools.DistCp#deleteNonexisting we serialize FileStatus objects when the path is all we need.

The performance problem comes from org.apache.hadoop.fs.RawLocalFileSystem.RawLocalFileStatus#write which tries to retrieve file permissions by issuing a "ls -ld <path>" which is painfully slow.

Changed that to just serialize Path and not FileStatus.

Second problem

To delete the files we invoke the "hadoop" command line tool with option "-rmr <path>". Again, for each file.

Changed that to dstfs.delete(path, true)