Accession Schema Registry

This schema registry stores schemas in a Git repository. It consists of these components:

• A Maven plugin puts schemas into the schema registry.

• A server provides schemas from the schema registry. It exposes an API compatible with the Confluent schema registry.

Schema registry Maven plugin

This Maven plugin puts a schema into the schema registry. If a new schema is incompatible with registered schemas, then the plugin fails the Maven build.

<plugin>
  <groupId>com.github.pukkaone.accession</groupId>
  <artifactId>schema-registry-maven-plugin</artifactId>
  <version>${accession.version}</version>
  <configuration>
    <compatibility>FORWARD</compatibility>
    <registryRepositories>
      <registryRepository>
        <projectBranchPattern>main</projectBranchPattern>
        <registryUri>ssh://[email protected]/example/schema-registry.git</registryUri>
        <registryBranch>main</registryBranch>
        <mutableVersions>false</mutableVersions>
      </registryRepository>
      <registryRepository>
        <projectBranchPattern>.*</projectBranchPattern>
        <registryUri>ssh://[email protected]/example/schema-registry.git</registryUri>
        <registryBranch>develop</registryBranch>
        <mutableVersions>true</mutableVersions>
      </registryRepository>
    </registryRepositories>
    <registrations>
      <registration>
        <subject>topic</subject>
        <version>1</version>
        <reflectClass>com.example.Event</reflectClass>
      </registration>
    </registrations>
  </configuration>
  <executions>
    <execution>
      <phase>deploy</phase>
      <goals>
        <goal>register</goal>
      </goals>
    </execution>
  </executions>
</plugin>

Parameter	Description
compatibility	How to compare new schema to registered schema for compatibility. Allowed values are BACKWARD, FORWARD, FULL. Default is FORWARD.
registryRepositories	Rules to select which Git repository and branch will store the schemas. Only the first matching rule applies. A rule matches if the projectBranchPattern regular expression matches the project’s checked-out Git branch.
projectBranchPattern	Regular expression to match project checked-out Git branch.
registryUri	Schema registry Git repository URI
registryBranch	Schema registry Git branch
mutableVersions	Whether to allow changing the schema of an existing version
registrations	Requests to register a schema in a subject and version
subject	Scope in which schemas can evolve. If the subject does not end with -key or -value, then -value is implicitly appended to the subject.
version	integer (0 to 999) uniquely identifying the version within the subject
reflectClass	Java class to introspect to generate Avro schema

The above example shows the intent to forbid changing schemas registered in the main branch of the Git repository, by setting the mutableVersions parameter to false. If the version parameter specifies a version already existing in the schema registry, then the plugin verifies the schema to be registered is identical to the schema in the existing version. An attempt to register a different schema in an existing version causes the plugin to fail the Maven build.

To allow work in progress schema changes to a version, the mutableVersions parameter is true for the develop branch of the Git repository. If the version parameter specifies a version already existing in the schema registry, then the plugin replaces the schema in that version.