SpringBoot Embedded Kafka to produce Event using Avro Schema

Question

I have created the below test class to produce an event using AvroSerializer.

@SpringBootTest
@EmbeddedKafka(partitions = 1, brokerProperties = { "listeners=PLAINTEXT://localhost:9092", "port=9092" })
@TestPropertySource(locations = ("classpath:application-test.properties"))
@ContextConfiguration(classes = { TestAppConfig.class })
@DirtiesContext
@TestInstance(TestInstance.Lifecycle.PER_CLASS)
class EntitlementEventsConsumerServiceImplTest {


    @Autowired
    EmbeddedKafkaBroker embeddedKafkaBroker;

    @Bean
    MockSchemaRegistryClient mockSchemaRegistryClient() {
        return new MockSchemaRegistryClient();
    }

    @Bean
    KafkaAvroSerializer kafkaAvroSerializer() {
        return new KafkaAvroSerializer(mockSchemaRegistryClient());
    }

    @Bean
    public DefaultKafkaProducerFactory producerFactory() {
        Map<String, Object> props = KafkaTestUtils.producerProps(embeddedKafkaBroker);
        props.put(KafkaAvroSerializerConfig.AUTO_REGISTER_SCHEMAS, false);
        return new DefaultKafkaProducerFactory(props, new StringSerializer(), kafkaAvroSerializer());
    }

    @Bean
    public KafkaTemplate<String, ApplicationEvent> kafkaTemplate() {
        KafkaTemplate<String, ApplicationEvent> kafkaTemplate = new KafkaTemplate(producerFactory());
        return kafkaTemplate;
    }
}

But when I send an event using kafkaTemplate().send(appEventsTopic, applicationEvent);I am getting the below exception.

Caused by: io.confluent.kafka.schemaregistry.client.rest.exceptions.RestClientException: Schema Not Found; error code: 404001
    at io.confluent.kafka.schemaregistry.client.MockSchemaRegistryClient.getIdFromRegistry(MockSchemaRegistryClient.java:79)
    at io.confluent.kafka.schemaregistry.client.MockSchemaRegistryClient.getId(MockSchemaRegistryClient.java:273)
    at io.confluent.kafka.serializers.AbstractKafkaAvroSerializer.serializeImpl(AbstractKafkaAvroSerializer.java:82)
    at io.confluent.kafka.serializers.KafkaAvroSerializer.serialize(KafkaAvroSerializer.java:53)
    at org.apache.kafka.common.serialization.Serializer.serialize(Serializer.java:62)
    at org.apache.kafka.clients.producer.KafkaProducer.doSend(KafkaProducer.java:902)
    at org.apache.kafka.clients.producer.KafkaProducer.send(KafkaProducer.java:862)
    at org.springframework.kafka.core.DefaultKafkaProducerFactory$CloseSafeProducer.send(DefaultKafkaProducerFactory.java:781)
    at org.springframework.kafka.core.KafkaTemplate.doSend(KafkaTemplate.java:562)
    at org.springframework.kafka.core.KafkaTemplate.send(KafkaTemplate.java:363)

When I use MockSchemaRegistryClient why it is trying to lookup the schema?

Answer 1

   schema.registry.url= mock://localhost.something

Basically anything with mock as prefix will do the job. Refer to this https://github.com/confluentinc/schema-registry/blob/master/avro-serializer/src/main/java/io/confluent/kafka/serializers/AbstractKafkaAvroSerDeConfig.java

Also set auto.register.schemas=true

Answer 2

You are setting the producer not to try and auto register new schema on producing the message , so it just trying to fetch from the SR and did not find its schema on the SR.

---

also did not see you setup schema registry URL guess its taking default values

---

To your question the mock is imitating the work of real schema registry, but has its clear disadvantages

/**

• Mock implementation of SchemaRegistryClient that can be used for tests. This version is NOT
• thread safe. Schema data is stored in memory and is not persistent or shared across instances. */

You may look on the document for more information

https://github.com/confluentinc/schema-registry/blob/master/client/src/main/java/io/confluent/kafka/schemaregistry/client/MockSchemaRegistryClient.java#L47