I'm about 70% sure that even only setting rebalance_cb: true means we need to implement assignment behaviour in the callback we provide.

(I think we even have to seek the appropriate offset on the partition ourselves - but haven't figured out a good way to test/debug this)

I'm about 70% sure that even only setting rebalance_cb: true means we need to implement assignment behaviour in the callback we provide.

Having a look here, it looks like it will use either eager or cooperative in the case that rebalance_cb is a boolean, and only if it's a function will it be expecting you to perform the rebalance yourself, does that sound right?

And then here in the node based rebalance code it handles the emit of the rebalance event. And if you don't specify anything you'll not have any events emitted and librdkafka will handle the rebalance internally(?)

Ah, and in the vanilla one it handles the boolean case https://github.com/Blizzard/node-rdkafka/blob/master/lib/kafka-consumer.js#L54

OK, 70% was an over-estimate 🤣