[MAPREDUCE-1707] TaskRunner can get NPE in getting ugi from TaskTracker

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.22.0
• Fix Version/s: 0.22.0
• Component/s: tasktracker
• Hadoop Flags: Reviewed
• Release Note: Fixed a bug that causes TaskRunner to get NPE in getting ugi from TaskTracker and subsequently crashes it resulting in a failing task after task-timeout period.
• Assignee: Vinod Kumar Vavilapalli
• Reporter: Amareshwari Sriramadasu
• Created: 15/Apr/10 08:58
• Updated: 12/Dec/11 06:19
• Resolved: 04/May/10 06:30

Description

The following code in TaskRunner can get NPE in the scenario described below.

      UserGroupInformation ugi = 
        tracker.getRunningJob(t.getJobID()).getUGI();

The scenario:
Tracker got a LaunchTaskAction; Task is localized and TaskRunner is started.
Then Tracker got a KillJobAction; This would issue a kill for the task. But, kill will be a no-op because the task did not actually start; The job is removed from runningJobs.
Then if TaskRunner calls tracker.getRunningJob(t.getJobID()), it will be null.

Instead of TaskRunner doing a back call to tasktracker to get the ugi, tracker.getRunningJob(t.getJobID()).getUGI(), ugi should be passed a parameter in the constructor of TaskRunner.

Issue Links

• incorporates: MAPREDUCE-1703 TaskRunner would crash in finally block if taskDistributedCacheManager is null