Hi, I'm trying to get a fairly simple example of using Kafka Streams with exactly once processing to work. I defined a setup where messages are being read from an input topic and two streams transform and output the result to their own output topic. In normal conditions this works fine, i.e. when publishing a message to the input topic, I get transformed messages in both of the output topics. Next I enabled exactly once processing by setting "processing.guarantee" to "exactly_once". To test this I'm deliberately throwing an exception when transforming the message in one of the stream processors. At a first glance the result is as expected, as neither of the output topics contain the transformed message and the application stops processing. However, when processing a message takes longer than the commit.interval.ms (which defaults to 100 when using exactly_once), then the transactional guarantee does not appear to be there and I get an output message in only one of the output topics (the one I for which I did not deliberately throw an exception while processing). I tested this by putting a Thread.sleep() before throwing the Exception. Can someone explain the relationship between this commit.interval.ms and exactly_once processing. I'd think it's rather strange that when processing takes longer than the commit.interval.ms you lose the atomicity of the transaction. I'm using Kafka 2.12-1.1.0 by the way.
Kind regards, Xander
