I have 2 Observations wrt consumer group rebalancing.
Observation 1 - I have multiple consumers on the same group , each subscribed to different topics. The entire Consumer group rebalance is expected to happen when I increase partition count for a topic. But I'm not observing this. The newly created partitions are never automatically assigned to the existing consumer. For them to be assigned I have to recreate the consumers again.
Observation 2 - I have a single consumer in a consumer group and this consumer is only subscribed to 1 topic. When I increase partition count on that topic, I am observing a rebalance within a couple of minutes.
Can anyone help me identify the problem here? I'm guessing that having multiple consumers subscribed to different topics is the issue here. Is my understanding right? Does anyone have an explanation for this behavior?