When one of your zookeeper nodes is sending you this message, that means that your Zookeeper cluster hasn’t started in the right order.
Solution: Restart your cluster (node per node), starting from node 1 (as stated in zoo.conf)
This problem is easy to diagnose. When the order was wrong you will get this output:
[myserver:myuser] ~: echo stat | nc localhost 2181 This ZooKeeper instance is not currently serving requests
After you’ve restarted all nodes (in the correct order), you will get this output:
[myserver:myuser] ~: echo stat | nc localhost 2181 |grep Mode Mode: follower [myserver:myuser] ~: echo stat | nc localhost 2181 |grep Mode Mode: leader
Hope this will help you out!