Zk reconnection problem

Version : 0.15.0
Problem description :

When zookeeper goes down and I restart zookeeper, I have to restart druid to reconnect to zk.This is a bad performance. Although there is a retry strategy, the Tate was stopped after the retry timeout. When zk service is restored, why not connect it automatically?You must restart the druid process to reconnect to zk

Start by reproducing the failure described for Druid 0.15.0: stop ZooKeeper, let the retry timeout expire, then restore ZooKeeper without restarting Druid. Trace the ZooKeeper connection and retry handling to determine why reconnection does not resume; done means Druid reconnects automatically after service restoration and the behavior is covered by a regression test.

Written by the indexing model from the issue text.