Cleanup the locking contention in the master
--------------------------------------------
Key: HBASE-3789
URL: https://issues.apache.org/jira/browse/HBASE-3789
Project: HBase
Issue Type: Improvement
Affects Versions: 0.90.2
Reporter: Jean-Daniel Cryans
Priority: Blocker
Fix For: 0.92.0
The new master uses a lot of synchronized blocks to be safe, but it only takes
a few jstacks to see that there's multiple layers of lock contention when a
bunch of regions are moving (like when the balancer runs). The main culprits
are regionInTransition in AssignmentManager, ZKAssign that uses ZKW.getZNnodes
(basically another set of region in transitions), and locking at the
RegionState level.
My understanding is that even tho we have multiple threads to handle regions in
transition, everything is actually serialized. Most of the time, lock holders
are talking to ZK or a region server, which can take a few milliseconds.
A simple example is when AssignmentManager wants to update the timers for all
the regions on a RS, it will usually be waiting on another thread that's
holding the lock while talking to ZK.
--
This message is automatically generated by JIRA.
For more information on JIRA, see: http://www.atlassian.com/software/jira
