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https://issues.apache.org/jira/browse/HBASE-3789?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Jean-Daniel Cryans updated HBASE-3789:
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Attachment: HBASE-3789-trunk.patch
Patch for trunk with the split fixes. I had to remove a test because it wasn't
an issue anymore (the master now creates the znode when closing a region), then
I had to do a bunch of fixes for AssignmentManager for cases when we report
regions that are already split or skipped steps and finally I added the part of
the code that waits for the master to delete the znode.
One thing I might do further cleanup on is the latter part of SplitTransaction
that has a few methods that all look the same. Also I'm not thrilled having to
do a sleep to wait on the master, but that was the easiest way.
> 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
> Assignee: Jean-Daniel Cryans
> Priority: Blocker
> Fix For: 0.92.0
>
> Attachments: HBASE-3789-trunk.patch, HBASE-3789-v3-0.90.patch
>
>
> 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.
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