Confluent Schema Registry

To run an instance of Schema Registry against a local Kafka cluster using the default configuration, use the following Maven command:

mvn exec:java -pl :kafka-schema-registry -Dexec.args="config/schema-registry.properties"

To build the project using Maven, ensure you have the necessary dependencies (like common and rest-utils) installed. Use the following commands:

• Compile: mvn compile
• Test: mvn test
• Package: mvn package [-DskipTests]
• Standalone Fat JAR: mvn package -P standalone [-DskipTests] (generates a single JAR with all dependencies).

The Schema Registry JMH microbenchmarks can be executed directly from the SerdeBenchmark.java file using an IDE like IntelliJ, or via the command line after building the module to produce target/benchmarks.jar.

java -jar ./target/benchmarks.jar

You can filter the benchmarks by specifying parameters. For example, to run only the AVRO serialization benchmarks, use the -p flag with the serializationFormat parameter set to AVRO.

java -jar ./target/benchmarks.jar -p serializationFormat=AVRO

Schemas can be retrieved in several ways:

• By Global ID: Use GET /schemas/ids/{id} to fetch a schema by its unique identifier.
• By Version: Use GET /subjects/{subject}/versions/{version} to fetch a specific version of a subject's schema.
• By Latest: Use GET /subjects/{subject}/versions/latest to fetch the most recently registered version for a subject.

# Fetch a schema by globally unique id 1
$ curl -X GET http://localhost:8081/schemas/ids/1

# Fetch version 1 of the schema registered under subject "Kafka-value"
$ curl -X GET http://localhost:8081/subjects/Kafka-value/versions/1

# Fetch the most recently registered schema under subject "Kafka-value"
$ curl -X GET http://localhost:8081/subjects/Kafka-value/versions/latest

To check if a new schema is compatible with the current latest schema of a subject, send a POST request to /compatibility/subjects/{subject}/versions/latest with the new schema in the body. The response will indicate if it is compatible.

# Test compatibility of a schema with the latest schema under subject "Kafka-value"
$ curl -X POST -H "Content-Type: application/vnd.schemaregistry.v1+json" \
    --data '{"schema": "{\"type\": \"string\"}"}' \
    http://localhost:8081/compatibility/subjects/Kafka-value/versions/latest

To register a new version of a schema under a specific subject (e.g., Kafka-key or Kafka-value), send a POST request to the /subjects/{subject}/versions endpoint. The request must include the Content-Type: application/vnd.schemaregistry.v1+json header and a JSON body containing the schema string.

# Register a new version of a schema under the subject "Kafka-key"
$ curl -X POST -H "Content-Type: application/vnd.schemaregistry.v1+json" \
    --data '{"schema": "{\"type\": \"string\"}"}' \
    http://localhost:8081/subjects/Kafka-key/versions

You can retrieve a list of all registered subjects using a GET request to /subjects. To see all versions registered under a specific subject, use GET /subjects/{subject}/versions.

# List all subjects
$ curl -X GET http://localhost:8081/subjects

# List all schema versions registered under the subject "Kafka-value"
$ curl -X GET http://localhost:8081/subjects/Kafka-value/versions

You can remove specific versions or entire subjects:

• Delete a specific version: Use DELETE /subjects/{subject}/versions/{version}.
• Delete all versions of a subject: Use DELETE /subjects/{subject}.

# Delete version 3 of the schema registered under subject "Kafka-value"
$ curl -X DELETE http://localhost:8081/subjects/Kafka-value/versions/3

# Delete all versions of the schema registered under subject "Kafka-value"
$ curl -X DELETE http://localhost:8081/subjects/Kafka-value

Compatibility settings can be managed at the global level or per subject:

• Global Config: Use GET /config to view and PUT /config to update global compatibility requirements.
• Subject-specific Config: Use PUT /config/{subject} to update compatibility requirements for a specific subject.

# Get top level config
$ curl -X GET http://localhost:8081/config

# Update compatibility requirements globally
$ curl -X PUT -H "Content-Type: application/vnd.schemaregistry.v1+json" \
    --data '{"compatibility": "NONE"}' \
    http://localhost:8081/config

# Update compatibility requirements under the subject "Kafka-value"
$ curl -X PUT -H "Content-Type: application/vnd.schemaregistry.v1+json" \
    --data '{"compatibility": "BACKWARD"}' \
    http://localhost:8081/config/Kafka-value

The ClientConfig class is used to parse configuration properties required by Kafka clients used in the leader election process. It extends Kafka's AbstractConfig and supports standard Kafka client configurations, including SSL and SASL support.

When initializing the configuration, you can provide a map of properties. The class includes several default values for network and retry behaviors.