...
- To increase or reduce the size of the voter set
- To change quorum membership in the case of failures (e.g. disaster recovery)
- To switch between dedicated deployment and mixed deployment easily, with making controller nodes standalone or integrate with data nodes
Zookeeper itself began supporting dynamic reconfiguration in 3.5, so this is also about reaching parity with the capabilities Kafka has today by leveraging Zookeeper. Finally, dynamic reassignment is also a prerequisite to making Raft-based replication available to local topic partitions.
...