Question about heartbeat between HBase masters and Zookeeper

[Yongcheng Li]

I am testing my multi-master HBase configuration and want to know how HBase 
master keep its Zookeeper session alive. Does the master (version .94 or later) 
send heartbeat message to ZooKeeper periodically? If yes, how often does it 
send the heartbeat message? If not, how does it present the session from 
expiring?

Thanks!

Yongcheng Li