[HADOOP-9022] Hadoop distcp tool fails to copy file if -m 0 specified

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.23.1, 0.23.3, 0.23.4
• Fix Version/s: 2.0.3-alpha, 0.23.5
• Assignee: Jonathan Turner Eagles
• Reporter: Haiyang Jiang
• Created: 09/Nov/12 04:00
• Updated: 03/Sep/14 23:19
• Resolved: 12/Nov/12 22:52

Description

When trying to copy file using distcp on H23, if -m 0 is specified, distcp will just spawn 0 mapper tasks and the file will not be copied.
But this used to work before H23, even when -m 0 specified, distcp will always copy the files.
Checked the code of DistCp.java
Before the rewrite, it set the number maps at least to 1
job.setNumMapTasks(Math.max(numMaps, 1));

But in the newest code, it just takes the input from user:
job.getConfiguration().set(JobContext.NUM_MAPS,
String.valueOf(inputOptions.getMaxMaps()));