Reactive ReplyingKafkaTemplate

[dnitzan]

Currently, ReplyingKafkaTemplate.sendAndReceive returns a RequestReplyFuture. This issue is a request for a reactive interface that would return Mono and/or Flux types instead. Potentially utilizing reactor-kafka to ensure fully non-blocking I/O. It would be very helpful for WebFlux services that need to interact with Kafka in a request/response manner and will enable such services to use Reactor types all the way throughout request/response handling.

[garyrussell]

The RequestReplyFuture has a nested ListenableFuture (for the send result).

I am not sure how we can handle that with Mono<?> (but my knowledge of Reactor is limited).

[ssljivic]

Using reactor-kafka for tequest-reply is really a missing link between webflux and kafka. Is this something on your roadmap?

[artembilan]

It is. May be next 2.4 version.
Anyway I want to share my understanding on the matter.
The Spring Kafka and Reactor Kafka is nothing more than wrappers around standard Apache Kafka client.
There is nothing reactive over there to have truly in back-preasure behavior.

Anyway Apache Kafka client is an async by nature and that was a reason to just wrap it into Reactors Flux and Mono types to open access to Apache Kafka from Reactive Streams world.

My point is that even if we don't have this ReplyingKafkaTemplate, there is not going to be too much runtime difference in the end if you would use already existing ReplyingKafkaTemplate.sendAndReceive() in the flatMap() of the request Flux in webflux application.