Simple embedded Kafka test example with spring boot - 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.

Answer 4

In integration testing, having fixed ports like 9092 is not recommended because multiple tests should have the flexibility to open their own ports from embedded instances. So, following implementation is something like that,
NB: this implementation is based on junit5(Jupiter:5.7.0) and spring-boot 2.3.4.RELEASE
TestClass:
#EnableKafka
#SpringBootTest(classes = {ConsumerTest.Config.class, Consumer.class})
#EmbeddedKafka(
partitions = 1,
controlledShutdown = false)
#TestInstance(TestInstance.Lifecycle.PER_CLASS)
public class ConsumerTest {
#Autowired
private EmbeddedKafkaBroker kafkaEmbedded;
#Autowired
private KafkaListenerEndpointRegistry kafkaListenerEndpointRegistry;
#BeforeAll
public void setUp() throws Exception {
for (final MessageListenerContainer messageListenerContainer : kafkaListenerEndpointRegistry.getListenerContainers()) {
ContainerTestUtils.waitForAssignment(messageListenerContainer,
kafkaEmbedded.getPartitionsPerTopic());
}
}
#Value("${topic.name}")
private String topicName;
#Autowired
private KafkaTemplate<String, Optional<Map<String, List<ImmutablePair<String, String>>>>> requestKafkaTemplate;
#Test
public void consume_success() {
requestKafkaTemplate.send(topicName, load);
}
#Configuration
#Import({
KafkaListenerConfig.class,
TopicConfig.class
})
public static class Config {
#Value(value = "${spring.kafka.bootstrap-servers}")
private String bootstrapAddress;
#Bean
public ProducerFactory<String, Optional<Map<String, List<ImmutablePair<String, String>>>>> requestProducerFactory() {
final Map<String, Object> configProps = new HashMap<>();
configProps.put(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG, bootstrapAddress);
configProps.put(ProducerConfig.KEY_SERIALIZER_CLASS_CONFIG, StringSerializer.class);
configProps.put(ProducerConfig.VALUE_SERIALIZER_CLASS_CONFIG, JsonSerializer.class);
return new DefaultKafkaProducerFactory<>(configProps);
}
#Bean
public KafkaTemplate<String, Optional<Map<String, List<ImmutablePair<String, String>>>>> requestKafkaTemplate() {
return new KafkaTemplate<>(requestProducerFactory());
}
}
}
Listener Class:
#Component
public class Consumer {
#KafkaListener(
topics = "${topic.name}",
containerFactory = "listenerContainerFactory"
)
#Override
public void listener(
final ConsumerRecord<String, Optional<Map<String, List<ImmutablePair<String, String>>>>> consumerRecord,
final #Payload Optional<Map<String, List<ImmutablePair<String, String>>>> payload
) {
}
}
Listner Config:
#Configuration
public class KafkaListenerConfig {
#Value(value = "${spring.kafka.bootstrap-servers}")
private String bootstrapAddress;
#Value(value = "${topic.name}")
private String resolvedTreeQueueName;
#Bean
public ConsumerFactory<String, Optional<Map<String, List<ImmutablePair<String, String>>>>> resolvedTreeConsumerFactory() {
final Map<String, Object> props = new HashMap<>();
props.put(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG, bootstrapAddress);
props.put(ConsumerConfig.GROUP_ID_CONFIG, resolvedTreeQueueName);
return new DefaultKafkaConsumerFactory<>(props, new StringDeserializer(), new CustomDeserializer());
}
#Bean
public ConcurrentKafkaListenerContainerFactory<String, Optional<Map<String, List<ImmutablePair<String, String>>>>> resolvedTreeListenerContainerFactory() {
final ConcurrentKafkaListenerContainerFactory<String, Optional<Map<String, List<ImmutablePair<String, String>>>>> factory = new ConcurrentKafkaListenerContainerFactory<>();
factory.setConsumerFactory(resolvedTreeConsumerFactory());
return factory;
}
}
TopicConfig:
#Configuration
public class TopicConfig {
#Value(value = "${spring.kafka.bootstrap-servers}")
private String bootstrapAddress;
#Value(value = "${topic.name}")
private String requestQueue;
#Bean
public KafkaAdmin kafkaAdmin() {
Map<String, Object> configs = new HashMap<>();
configs.put(AdminClientConfig.BOOTSTRAP_SERVERS_CONFIG, bootstrapAddress);
return new KafkaAdmin(configs);
}
#Bean
public NewTopic requestTopic() {
return new NewTopic(requestQueue, 1, (short) 1);
}
}
application.properties:
spring.kafka.bootstrap-servers=${spring.embedded.kafka.brokers}
This assignment is the most important assignment that would bind the embedded instance port to the KafkaTemplate and, KafkaListners.
Following the above implementation, you could open dynamic ports per test class and, it would be more convenient.