[MAPREDUCE-475] JobConf should validate key names in well-defined namespaces and warn on misspelling

• Type: Improvement
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Assignee: Unassigned
• Reporter: Aaron Kimball
• Created: 21/Feb/08 04:12
• Updated: 17/Jul/14 21:04
• Resolved: 17/Jul/14 21:04

Description

A discussion on the mailing list reveals that some configuration strings in the JobConf are deprecated over time and new configuration names replace them:

e.g., "mapred.output.compression.type" is now replaced with "mapred.map.output.compression.type"

Programmers who have been manually specifying the former string, however, receive no diagnostic output during testing to suggest that their compression type is being silently ignored.

It would be desirable to notify developers of this change by printing a warning message when deprecated configuration names are used in a newer version of Hadoop. More generally, when any configuration string in the mapred.*, fs.*, dfs.*, etc namespaces are provided by a user and are not recognized by Hadoop, it is desirable to print a warning, to indicate malformed configurations. No warnings should be printed when configuration keys are in user-defined namespaces (e.g., "myprogram.mytask.myvalue").

Issue Links

• is related to: HADOOP-3582 Improve how Hadoop gets configured