I'm looking at using BK for a WAL-like component for a document store. It does involve multiple (many!) consumers tailing the log, but unlike your typical Kafka setup, there's need for no partitioning.

I was unsure of whether BK provides an API that's nice to use for non-Java languages like Go and Rust, which is what we use. Apache projects written in Java (or Scala), particularly those in the Hadoop ecosystem, tend to be very JVM-centric, and often they're impossible to use from other languages because there's no non-Java API. Kafka is an outlier here, but it certainly started out with a Java-only client and it took years for non-Java clients to mature enough to be usable.

I thought I saw that BK had a REST API, but now I see that it's just an admin API. From what I can tell, it's exactly like every other Apache Java project — there's a big monolithic Java client that's tightly coupled with the server, and to write a client in any other language you'd have to reverse-engineer it and essentially port the whole thing, because it's a "fat client" — it looks like it talks directly to ZooKeeper and "bookies", and has a lot of logic built in. The Bookie protocol looks like it's binary and hand-coded (not gRPC or anything nice). So disappointing! /rant

Edit: Looks like the files I was looking at are generated from Protobuf. So, yay. Unfortunately, that's just the Bookie protocol. The main client is still fat and in Java.