[jira] [Created] (HBASE-8368) Improve ZK notification handling in Master

["Jeffrey Zhong (JIRA)" <ji...@apache.org>]

Jeffrey Zhong created HBASE-8368:
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             Summary: Improve ZK notification handling in Master
                 Key: HBASE-8368
                 URL: https://issues.apache.org/jira/browse/HBASE-8368
             Project: HBase
          Issue Type: Improvement
          Components: master
    Affects Versions: 0.95.0
            Reporter: Jeffrey Zhong
            Assignee: Jeffrey Zhong
             Fix For: 0.98.0


In ZooKeeperWatcher, we handle ZK notifications in a single queue and each listener is handling notifications synchronously. 

This cause potential performance issue if Master is handling an event which may jam the queue so that ZooKeeperWatcher won't get new notifications in time. For example, we have several region un-assigned notifications in pipeline and logsplitting or SSH handling etc handling will be delayed.

I'm proposing:

During registerListeners, we can let a user to choose which queue current listener want to register. For example, 
registerListener(QueueName, ZNodePathPrefix, listener);

Such as:
registerListener("unsigned_regions", "/hbase/unassigned", AMlistener);
registerListener("logSplitting", "/hbase/splitlog", LogSplittingManagerlistener);
...

For each queue, we use a single thread(consumer) to process events in order.

The ZNodePathPrefix is to pre-filter out notifications that current listener is only interested in. 

For listeners without specifying a queue name, the listener will be put on a new "default" queue.

Please let me know if you have better ideas!
Thanks.

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