reconfigEnabled = false (not explicitly setting, relying on the default value).
Install 3 zookeeper servers with 3 zk information in all the 3 zookeeper quorum servers.
Do a rolling scale up of cluster from 3 to 5 with below steps.
1. Install 4th zookeeper with servers list of 1,2,3,4,5
2. Install 5th zookeeper with servers list of 1,2,3,4,5
3. Do a rolling restart of servers 1 2 & 3 with servers list of 1,2,3,4,5.
Result/Behavior: quorum is lost.
With this https://issues.apache.org/jira/browse/ZOOKEEPER-2819
description points at a PR https://github.com/apache/zookeeper/pull/292
which should have this issue of rolling restart fixed without dynamic reconfiguration feature enabled.
We still see quorum loss issues without dynamic reconfig feature enabled.