ksqlDB-GraphQL-poc VS rust-rdkafka

In order to prepare for a future blog with Confluent I wanted to play around with ksqlDB, which was the perfect opportunity to use the Rust library in a less trivial way. As it turned out there is even a library for communicating with ksqlDB from rust, using the Rest API. The PoC project for this contains some code to put protobuf data on a topic.

I use this library a lot and it's got some nice touches for how to handle wrapping a C library: https://github.com/fede1024/rust-rdkafka

For this example, we're using rdkafka to build producers and consumers, because it allows us to specify custom headers for each record.

kafka

You might find https://crates.io/crates/rdkafka helpful

I am playing with tokio and rust-rdkafka library, following the examples like this one: https://github.com/fede1024/rust-rdkafka/blob/6fb2c37/examples/asynchronous_processing.rs

The source for the current version of the library can be found on Github. I had to increase the major version because I needed to break the API in order to support all formats supported by the current Schema Registry version. I also added the possibility to set an API key, so it can be used with Confluent Cloud, the cloud offering from Confluent. As part of the latest major refactoring it's also supporting async. This might improve performance of your app, and is also the default for the major Kafka client, more information about why you would want to use async can be found in the async book. The schemas retrieved from the Schema Registry are cached. This way the schema is only retrieved once for each id, and reused for other messages with the same id.

What's wrong with rust-rdkafka?

This is a two-part series to help you get started with Rust and Kafka. We will be using the rust-rdkafka crate which itself is based on librdkafka (C library).