[HBASE-16598] Enable zookeeper useMulti always and clean up in HBase code

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 2.0.0
• Hadoop Flags: Incompatible change, Reviewed

Release Note

Deprecate the configuration property 'hbase.zookeeper.useMulti'.
useMulti will always be enabled. ZooKeeper 3.4.x and newer is required.

Internal:

The ZKUtil#multiOrSequential(ZooKeeperWatcher zkw, List<ZKUtilOp> ops, boolean runSequentialOnMultiFailure) will not check 'hbase.zookeeper.useMulti' anymore, and will always use multi.
It can still fall back to sequential operations if:

RunSequentialOnMultiFailure is true
On calling multi, we get a ZooKeeper exception that can be handled by a sequential call.

• Assignee: Jerry He
• Reporter: Jerry He
• Created: 09/Sep/16 18:30
• Updated: 09/Mar/17 22:52
• Resolved: 18/Sep/16 00:30

Description

We have zookeeper useMulti default true since HBase 1.0.0
And in our Doc, "ZooKeeper 3.4.x is required as of HBase 1.0.0"
The benefit of useMulti is obvious.
Let's clean up the code to remove useMulti false case so that we don't have to continue with the hassle of maintaining two version of the code (e.g. in replication) . No go back to pre 3.4.x Zookeeper.