v.22.10Improvement

Improved Reactivity for ZooKeeper Connection Reestablishment

Made reestablishing a new connection to ZooKeeper more reactive in case of expiration of the previous one. Previously there was a task which spawns every minute by default and thus a table could be in readonly state for about this time. #41092 (Nikita Mikhaylov).
Improved the reestablishment of ZooKeeper connections to be more reactive upon session expiration, reducing the delay before tables become writable again.

Why it matters

Previously, ClickHouse reconnected to ZooKeeper on a fixed schedule (every minute), which caused tables to remain in a readonly state for up to that duration after a session expiration. This feature makes reconnect attempts immediately reactive after session expiration, minimizing downtime and improving availability.

How to use it

This improvement is implemented internally and does not require user configuration. Users benefit from faster recovery after ZooKeeper session expiration automatically upon updating to the new version.