ksqlDB-GraphQL-poc VS obm_confluent_blog

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.

So what is actually the Schema Registry? And how does it help to make sense of binary data? In essence Schema Registry is an application with some Rest endpoints, from which schema's can be registered and retrieved. It used to only support Apache Avro. Later support for Protobuf and JSON Schema was added. Part of the same Github project, and what makes Schema Registry easy to use, is a Collection of Java classes that are used to go from bytes to typed objects and vice versa. There are several classes that support Kafka Streams and ksqlDB next to the more low level Kafka [Producer(https://kafka.apache.org/documentation/#producerapi) and Consumer clients. There are more advanced use cases, but basically you supply the url for the Schema Registry, and the library will handle the rest. For producing data this will mean optionally register a new schema too get the correct id. The consumer will use the encoded id to fetch the schema used to produce the data. It can also be used with other frameworks like Spring Cloud Stream. For example in the Kotlin Command Handler by using the SpecificAvroSerde class. You might need to set additional properties to get this working.