[MAPREDUCE-2705] tasks localized and launched serially by TaskLauncher - causing other tasks to be delayed

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.20.205.0
• Fix Version/s: 0.20.205.0, 0.23.0
• Component/s: tasktracker
• Assignee: Thomas Graves
• Reporter: Thomas Graves
• Created: 18/Jul/11 19:40
• Updated: 19/Oct/11 00:26
• Resolved: 04/Aug/11 01:33

Description

The current TaskLauncher serially launches new tasks one at a time. During the launch it does the localization and then starts the map/reduce task. This can cause any other tasks to be blocked waiting for the current task to be localized and started. In some instances we have seen a task that has a large file to localize (1.2MB) block another task for about 40 minutes. This particular task being blocked was a cleanup task which caused the job to be delayed finishing for the 40 minutes.