Group instance ID support (group.instance.id) (static membership)

[anoskov]

Hello!
It is possible to add group instance ID support for static membership. This allows in some cases reduce consumer rebalances.

Details: KIP-345

[zmstone]

The underlying protocol library already supports it,
however we do not have the plan to support it in brod yet, not at the moment.

ref: https://github.com/kafka4beam/kafka_protocol/blob/7147d6e16652b9b1c39758250bdf93ee934ec706/src/kpro_schema.erl#L499-L517

[anoskov]

@zmstone thanks for reply!
Correctly I understand that we should pass this to coordinators state and after to join_group and sync_group requests body?

https://github.com/kafka4beam/brod/blob/master/src/brod_group_coordinator.erl#L616
https://github.com/kafka4beam/brod/blob/master/src/brod_group_coordinator.erl#L652

[zmstone]

Hi @anoskov
I'm afraid it's more than just adding the fields.

I had a quick look at KIP before, and just quickly revisited it,
It seems that "Client Behavior Changes" implies brod_group_coordinator should change in its rebalance behaviours.