v.20.10Improvement

Provide load_balancing_first_offset query setting for replica control

Provide a load_balancing_first_offset query setting to explicitly state what the first replica is. It's used together with FIRST_OR_RANDOM load balancing strategy, which allows to control replicas workload. #14867 (Amos Bird).
Introduces the load_balancing_first_offset query setting to explicitly define the first replica used with the FIRST_OR_RANDOM load balancing strategy in ClickHouse.

Why it matters

This feature allows precise control over which replica is considered the "first" when using the FIRST_OR_RANDOM load balancing strategy. It helps in managing replicas' workload by explicitly setting the starting offset, improving query distribution and potentially optimizing resource usage.

How to use it

Users can enable this feature by setting the load_balancing_first_offset query setting to an integer value representing the desired first replica offset. This setting should be used together with the load_balancing strategy set to FIRST_OR_RANDOM in their queries or configuration.