Simple embedded Kafka test example with spring boot

Question

Edit FYI: working gitHub example

---

I was searching the internet and couldn't find a working and simple example of an embedded Kafka test.

My setup is:

• Spring boot
• Multiple @KafkaListener with different topics in one class
• Embedded Kafka for test which is starting fine
• Test with Kafkatemplate which is sending to topic but the @KafkaListener methods are not receiving anything even after a huge sleep time
• No warnings or errors are shown, only info spam from Kafka in logs

Please help me. There are mostly over configured or overengineered examples. I am sure it can be done simple. Thanks, guys!

@Controller
public class KafkaController {

    private static final Logger LOG = getLogger(KafkaController.class);

    @KafkaListener(topics = "test.kafka.topic")
    public void receiveDunningHead(final String payload) {
        LOG.debug("Receiving event with payload [{}]", payload);
        //I will do database stuff here which i could check in db for testing
    }
}

---

private static String SENDER_TOPIC = "test.kafka.topic";

@ClassRule
public static KafkaEmbedded embeddedKafka = new KafkaEmbedded(1, true, SENDER_TOPIC);

@Test
    public void testSend() throws InterruptedException, ExecutionException {

        Map<String, Object> senderProps = KafkaTestUtils.producerProps(embeddedKafka);

        KafkaProducer<Integer, String> producer = new KafkaProducer<>(senderProps);
        producer.send(new ProducerRecord<>(SENDER_TOPIC, 0, 0, "message00")).get();
        producer.send(new ProducerRecord<>(SENDER_TOPIC, 0, 1, "message01")).get();
        producer.send(new ProducerRecord<>(SENDER_TOPIC, 1, 0, "message10")).get();
        Thread.sleep(10000);
    }

Answer 1

Embedded Kafka tests work for me with below configs,

Annotation on test class

@EnableKafka
@SpringBootTest(classes = {KafkaController.class}) // Specify @KafkaListener class if its not the same class, or not loaded with test config
@EmbeddedKafka(
    partitions = 1, 
    controlledShutdown = false,
    brokerProperties = {
        "listeners=PLAINTEXT://localhost:3333", 
        "port=3333"
})
public class KafkaConsumerTest {
    @Autowired
    KafkaEmbedded kafkaEmbeded;

    @Autowired
    KafkaListenerEndpointRegistry kafkaListenerEndpointRegistry;

Before annotation for setup method

@Before
public void setUp() throws Exception {
  for (MessageListenerContainer messageListenerContainer : kafkaListenerEndpointRegistry.getListenerContainers()) {
    ContainerTestUtils.waitForAssignment(messageListenerContainer, 
    kafkaEmbeded.getPartitionsPerTopic());
  }
}

Note: I am not using @ClassRule for creating embedded Kafka rather auto-wiring
@Autowired embeddedKafka

@Test
public void testReceive() throws Exception {
     kafkaTemplate.send(topic, data);
}

Hope this helps!

Edit: Test configuration class marked with @TestConfiguration

@TestConfiguration
public class TestConfig {

@Bean
public ProducerFactory<String, String> producerFactory() {
    return new DefaultKafkaProducerFactory<>(KafkaTestUtils.producerProps(kafkaEmbedded));
}

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

Now @Test method will autowire KafkaTemplate and use is to send message

kafkaTemplate.send(topic, data);

Updated answer code block with above line

Answer 2

since the accepted answer doesn't compile or work for me. I find another solution based on https://blog.mimacom.com/testing-apache-kafka-with-spring-boot/ what I would like to share with you.

The dependency is 'spring-kafka-test' version: '2.2.7.RELEASE'

@RunWith(SpringRunner.class)
@EmbeddedKafka(partitions = 1, topics = { "testTopic" })
@SpringBootTest
public class SimpleKafkaTest {

    private static final String TEST_TOPIC = "testTopic";

    @Autowired
    EmbeddedKafkaBroker embeddedKafkaBroker;

    @Test
    public void testReceivingKafkaEvents() {
        Consumer<Integer, String> consumer = configureConsumer();
        Producer<Integer, String> producer = configureProducer();

        producer.send(new ProducerRecord<>(TEST_TOPIC, 123, "my-test-value"));

        ConsumerRecord<Integer, String> singleRecord = KafkaTestUtils.getSingleRecord(consumer, TEST_TOPIC);
        assertThat(singleRecord).isNotNull();
        assertThat(singleRecord.key()).isEqualTo(123);
        assertThat(singleRecord.value()).isEqualTo("my-test-value");

        consumer.close();
        producer.close();
    }

    private Consumer<Integer, String> configureConsumer() {
        Map<String, Object> consumerProps = KafkaTestUtils.consumerProps("testGroup", "true", embeddedKafkaBroker);
        consumerProps.put(ConsumerConfig.AUTO_OFFSET_RESET_CONFIG, "earliest");
        Consumer<Integer, String> consumer = new DefaultKafkaConsumerFactory<Integer, String>(consumerProps)
                .createConsumer();
        consumer.subscribe(Collections.singleton(TEST_TOPIC));
        return consumer;
    }

    private Producer<Integer, String> configureProducer() {
        Map<String, Object> producerProps = new HashMap<>(KafkaTestUtils.producerProps(embeddedKafkaBroker));
        return new DefaultKafkaProducerFactory<Integer, String>(producerProps).createProducer();
    }
}

Answer 3

I solved the issue now

@BeforeClass
public static void setUpBeforeClass() {
    System.setProperty("spring.kafka.bootstrap-servers", embeddedKafka.getBrokersAsString());
    System.setProperty("spring.cloud.stream.kafka.binder.zkNodes", embeddedKafka.getZookeeperConnectionString());
}

while I was debugging, I saw that the embedded kaka server is taking a random port.

I couldn't find the configuration for it, so I am setting the kafka config same as the server. Looks still a bit ugly for me.

I would love to have just the @Mayur mentioned line

@EmbeddedKafka(partitions = 1, controlledShutdown = false, brokerProperties = {"listeners=PLAINTEXT://localhost:9092", "port=9092"})

but can't find the right dependency in the internet.