[YARN-5938] Refactoring OpportunisticContainerAllocator to use SchedulerRequestKey instead of Priority and other misc fixes

• Type: Sub-task
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 2.9.0, 3.0.0-alpha2
• Assignee: Arun Suresh
• Reporter: Arun Suresh
• Created: 28/Nov/16 23:59
• Updated: 13/Nov/17 22:48
• Resolved: 27/Dec/16 20:47

Description

Minor code re-organization to do the following:

1. The OpportunisticContainerAllocatorAMService currently allocates outside the ApplicationAttempt lock maintained by the ApplicationMasterService. This should happen inside the lock.
2. Refactored out some code to simplify the allocate() method.
3. Removed some unused fields inside the OpportunisticContainerAllocator.
4. Re-organized some of the code in the OpportunisticContainerAllocatorAMService::allocate method to make it a bit more readable.
5. Moved SchedulerRequestKey to a new package, so it can be used by the OpportunisticContainerAllocator/Context.
6. Moved all usages of Priority in the OpportunisticContainerAllocator -> SchedulerRequestKey.