Hi Tomasz, Thanks for asking. This sounds like the situation that we fixed in Apache Kafka 3.0, with KIP-695 (https://cwiki.apache.org/confluence/display/KAFKA/KIP-695%3A+Further+Improve+Kafka+Streams+Timestamp+Synchronization).
Can you try upgrading and let us know if this fixes the problem? Thanks, -John On Mon, Sep 26, 2022, at 01:35, Tomasz Gac wrote: > Hi group, > > I wrote a simple kafka streams application with topology such as below: > > builder.addStateStore( >> Stores.keyValueStoreBuilder( >> Stores.persistentKeyValueStore("STORE"), >> Serdes.String(), Serdes.String()) >> .withLoggingEnabled(storeConfig))| > > > > builder.stream("TOPIC_1", Consumed.with(...)) >> .merge(builder.stream("TOPIC_2", Consumed.with(...)) >> .merge(builder.stream("TOPIC_3", Consumed.with(...)) >> .map(...) // stateless >> .transform(..., "STORE") // stateful > > .to("TOPIC_4"); > > > All input topics have 6 partitions, and for the purpose of testing, we are > producing data to partition number 5. > We are using kafka streams version 2.8.1, broker version 2.12-2.1.1 > > The application works as expected when it has caught up to the lag, eg. > when reset tool is used with --to-latest parameter. > However, when the application is processing the messages starting from the > earliest offset, the inputs are provided in batches such as: > > - ~1000 messages from TOPIC_1 > - ~1000 messages from TOPIC_2 > - ~1000 messages from TOPIC_3 > > All of the messages have timestamps provided in headers, so I would expect > the application to interleave the messages from these three topics so that > their timestamps are in the ascending order. > However, this is not the case that I am observing. The messages are > processed in batches. > > How do I configure my application so that it processes messages in order > when it is catching up to the lag?