[MAPREDUCE-7489] Exposing Default Handling of Misconfigurations to Users in MasterPrincipal

• Type: Improvement
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 3.3.6
• Component/s: mapreduce-client

Environment

Version: `3.3.6`
Location: `hadoop/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapred/Master.java`， in `getMasterPrincipal` method, from Line 51 - 59.

• Assignee: Unassigned
• Reporter: LoggingResearch
• Created: 04/Sep/24 05:30
• Updated: 04/Sep/24 05:30

Description

When users attempt to configure the MasterPrincipal for local mode using the system user root, they might set mapreduce.framework.name to local and mapreduce.jobtracker.kerberos.principal to root, following the configuration documentation. Although the job executes, it may not behave as expected. Users may spend considerable time troubleshooting before discovering that setting mapreduce.framework.name to classic yields the desired outcome. This confusion arises from the silent default handling in the code, which is counterintuitive, as "classic" is not typically associated with local mode. Even worse, there is no system output to indicate this default handling, leaving users puzzled.
 
Expected Behavior:
The system should provide output indicating to users any unseen default handling regarding MasterPrincipal.
 
How-to-Fix:
We propose improving system transparency by adding logging.