[HADOOP-3931] Bug in MapTask.MapOutputBuffer.collect leads to an unnecessary and harmful 'reset'

• Type: Bug
• Status: Closed
• Priority: Blocker
• Resolution: Fixed
• Affects Version/s: 0.17.1
• Fix Version/s: 0.17.2
• Hadoop Flags: Reviewed
• Assignee: Christopher Douglas
• Reporter: Arun Murthy
• Created: 09/Aug/08 19:21
• Updated: 08/Jul/09 16:52
• Resolved: 11/Aug/08 20:54

Description

The unnecessary reset of the io.sort.mb buffer when bufindex==bufvoid leads to wrong, very large, temporary key buffer being created and passed along to the Buffer.write. This causes MapBufferTooSmallException as the Buffer thinks there isn't enough space to write this record into. If a combiner is defined the record does not go through the combiner and hits the disk directly.

It's already fixed in hadoop-0.18.