Expose Consumer Assignment through ConsumerRegistry

[brianwyka]

Expose each consumer's subscriptions and assignment through the ConsumerRegistry keyed by client id. This information is hard to get since it can only be accessed from poll loop thread.

[graemerocher]

could you add a test?

[brianwyka]

Sure, I will do that.

[brianwyka]

@graemerocher, added a test as well as exposed the subscriptions (topics).

It seems that the subscriptions are available before the poll loop begins, and then the assignment becomes available within the poll loop after partitions have been assigned. Although, I'm not exactly sure, precisely, when the assignment is happening.

[brianwyka]

I'm looking to use this functionality within a custom health indicator which determines kafka health based on the existence of consumers of specific topics.

Based on configuration, you will be able to determine healthy if a specific topic is being consumed from.

Do you think that would be valuable to add here, or too specific of a use case?

[brianwyka]

This should be ready to go @graemerocher. I can follow up with another feature request for the kafka consumer health indicator if it seems to be useful.

[brianwyka]

@graemerocher can we get this in the next Micronaut release?