Improved ZooKeeper Load Balancing with AZ-aware Support

Why it matters

This feature ensures that the current ZooKeeper session does not expire prematurely until optimal nodes become available, regardless of the fallback_session_lifetime setting. It improves stability and efficiency by enabling availability zone-aware load balancing, reducing latency and increasing fault tolerance in distributed ClickHouse deployments.

How to use it

The improved ZooKeeper load balancing is enabled by default in the new version. Users benefit from AZ-aware balancing automatically. The fallback_session_lifetime parameter remains configurable to control session expiration timing under fallback conditions.