[HBASE-7271] Have a single executor for all zkWorkers in the assignment manager

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.95.2
• Fix Version/s: 0.95.0
• Component/s: master, Region Assignment
• Hadoop Flags: Reviewed
• Assignee: Nicolas Liochon
• Reporter: Nicolas Liochon
• Created: 04/Dec/12 15:06
• Updated: 23/Sep/13 18:30
• Resolved: 11/Dec/12 08:40

Description

The current strategy is to have an array of monothreaded executor, and hash the zk path to ensure that there are no two events on the same region executed in parallel

I think a single executor, as presented in the attached patch, is better because:

• we're guaranteed to use all threads at any time
• if managing one of the event takes longer that expected, the slowness is limited to this region, and not to all regions that have the same hashed/moduloed code
• For the nodeChildrenChanged, there is no need to choose randomly one of the worker (or, once again, the risk to get stuck if one of the event takes time to be managed).

Issue Links

• is required by: HBASE-5843 Improve HBase MTTR - Mean Time To Recover