When working with KafkaConsumer, we usually employ single thread both for reading and processing of messages. KafkaConsumer is not thread-safe, so using single thread fits in well. Downside of this approach is that you are limited to single thread for processing messages.
By decoupling consumption and processing, we can achieve processing parallelization with single consumer and get the most out of multi-core CPU architectures available today. While this can be very useful in certain use-case scenarios, it's not trivial to implement.
How do we use multiple threads with KafkaConsumer which is not thread safe? How do we react to consumer group rebalancing? Can we get desired processing and ordering guarantees? In this talk we 'll try to answer these questions and explore challenges we face on our path.