[HADOOP-5746] Errors encountered in MROutputThread after the last map/reduce call can go undetected

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 0.20.1
• Hadoop Flags: Reviewed

Release Note

If the child (streaming) process returns successfully and the MROutputThread throws an error, there was no way to detect that as all the IOExceptions was ignored. Such issues can occur when DFS clients were closed etc. Now a check for errors (in threads) is made before finishing off the task and an exception is thrown that fails he task.

• Assignee: Amar Kamat
• Reporter: Devaraj Das
• Created: 27/Apr/09 03:39
• Updated: 08/Jul/09 17:05
• Resolved: 04/Jun/09 12:45

Description

The framework map/reduce bridge methods make a check at the beginning of the respective methods whether MROutputThread encountered an exception while writing keys/values that the streaming process emitted. However, if the exception happens in MROutputThread after the last call to the map/reduce method, the exception goes undetected. An example of such an exception is an exception from the DFSClient that fails to write to a file on the HDFS.