[kitd]

My thoughts too.

> kafka compatible

Kafka is not a straightforward protocol and has a few odd niches. Not to mention that message formats have changed over the years. Even the base product has recently dropped support for some of the oldest API versions. And there are still plenty of clients out there using old versions of librdkafka (he says from experience).

So I'd be interested how (backward-)compatible they are.

[shortishly]

I agree that it isn't straight forward! Tansu uses the JSON protocol descriptors from Apache Kafka, generating ~60k LoC of Rust to represent the structures. It then uses a custom Serde encoder/decoder to implement the protocol: original, flexible and tag buffers formats for every API version (e.g., the 18 just in FETCH). It is based off spending the past ~10 years using Kafka, and writing/maintaining an Erlang client (there are no "good" Kafka clients for Erlang!). It also uses a bunch of collected protocol examples, to encode/decode during the tests. Tansu is also a Kafka proxy, which is also used to feed some of those tests.

Some of the detail: https://blog.tansu.io/articles/serde-kafka-protocol

However, there are definitely cases I am sure where Tansu isn't compatible. For example, Kafka UI (kafbat) reports a strange error when doing a fetch (despite actually showing the fetched data), which I've yet to get to the bottom of.

If you find any compatibility issues, then please raise an issue, and I can take a look.