Client-side schema enforcement

The information flow when you use schema registry is the same for all protocols that you use to publish or consume events from Azure Event Hubs.

The following diagram shows how the information flows when event producers and consumers use Schema Registry with the Kafka protocol using Avro serialization.

Producer

1. Kafka producer application uses KafkaAvroSerializer to serialize event data using the specified schema. Producer application provides details of the schema registry endpoint and other optional parameters that are required for schema validation.
2. The serializer looks for the schema in the schema registry to serialize event data. If it finds the schema, then the corresponding schema ID is returned. You can configure the producer application to auto register the schema with the schema registry if it doesn't exist.
3. Then the serializer prepends the schema ID to the serialized data that is published to the Event Hubs.

Consumer

1. Kafka consumer application uses KafkaAvroDeserializer to deserialize data that it receives from the event hub.
2. The deserializer uses the schema ID (prepended by the producer) to retrieve schema from the schema registry.
3. The deserializer uses the schema to deserialize event data that it receives from the event hub.
4. The schema registry client uses caching to prevent redundant schema registry lookups in the future.