I've set up a POC using KafkaStreams with microservices consuming and producing from/to topics. In the beginning I hadn't thought about partition strategy, and so I was using the DefaultPartitioner for producer partition assignments. My messages have keys (I use these for forking/joining), and the keys are time based UUIDs, this causes some rather uneven distribution on my topics. I looked around google and stumbled on KIP-369 (Alternative Partitioner to Support "Always Round-Robin" Selection) and figured that would be what I needed, so since 2.4 isn't out yet I borrowed the class from the PR on github, added it to my project and added the property to my config, like so:
streamProperties.put(ProducerConfig.PARTITIONER_CLASS_CONFIG, RoundRobinPartitioner.class.getCanonicalName()); And the round robin strategy works on a newly added topic, spreading messages evenly over 4 partitions. But, and I'm finally getting to my question, it doesn't seem to have any effect on existing topics, in other words, it seems to be continuing to use the DefaultPartitioner for topics created before I added the RoundRobinPartioner class to my project/properties. Is it me that just hasn't understood that it is impossible to change strategy for an existing partition or do I have to do something specific apart from re-deploying the Microservice containing the producer? Thanks Mikkel --
