Kafka Consumer with Circuit Breaker, Retry Patterns using Resilience4j - spring-boot

Question

I need some help in understanding how I can come up with a solution using Spring boot, Kafka, Resilence4J to achieve a microservice call from my Kafka Consumer. Let's say if the Microservice is down then I need to notify my Kafka consumer using a circuit breaker pattern to stop fetching the messages/events until the Microservice is up and running.

Answer 1

With Spring Kafka, you could use the pause and resume methods depending on the CircuitBreaker state transitions. The best way I found for this is to define it as "supervisor" with an #Configuration Annotation. Resilience4j is also used.
#Configuration
public class CircuitBreakerConsumerConfiguration {
public CircuitBreakerConsumerConfiguration(CircuitBreakerRegistry circuitBreakerRegistry, KafkaManager kafkaManager) {
circuitBreakerRegistry.circuitBreaker("yourCBName").getEventPublisher().onStateTransition(event -> {
switch (event.getStateTransition()) {
case CLOSED_TO_OPEN:
case CLOSED_TO_FORCED_OPEN:
case HALF_OPEN_TO_OPEN:
kafkaManager.pause();
break;
case OPEN_TO_HALF_OPEN:
case HALF_OPEN_TO_CLOSED:
case FORCED_OPEN_TO_CLOSED:
case FORCED_OPEN_TO_HALF_OPEN:
kafkaManager.resume();
break;
default:
throw new IllegalStateException("Unknown transition state: " + event.getStateTransition());
}
});
}
}
This is what I used in combination with a KafkaManager annotated with #Component.
#Component
public class KafkaManager {
private final KafkaListenerEndpointRegistry registry;
public KafkaManager(KafkaListenerEndpointRegistry registry) {
this.registry = registry;
}
public void pause() {
registry.getListenerContainers().forEach(MessageListenerContainer::pause);
}
public void resume() {
registry.getListenerContainers().forEach(MessageListenerContainer::resume);
}
}
In addition my consumer service looks like this:
#KafkaListener(topics = "#{'${topic.name}'}", concurrency = "1", id = "CBListener")
public void receive(final ConsumerRecord<String, ReplayData> replayData, Acknowledgment acknowledgment) throws
Exception {
try {
httpClientServiceCB.receiveHandleCircuitBreaker(replayData);
acknowledgement.acknowledge();
} catch (Exception e) {
acknowledgment.nack(1000);
}
}
And the #CircuitBreaker Annotation:
#CircuitBreaker(name = "yourCBName")
public void receiveHandleCircuitBreaker(ConsumerRecord<String, ReplayData> replayData) throws
Exception {
try {
String response = restTemplate.getForObject("http://localhost:8081/item", String.class);
} catch (Exception e ) {
// throwing the exception is needed to trigger the Circuit Breaker state change
throw new Exception();
}
}
And this is additionally supplemented by the following application.properties
resilience4j.circuitbreaker.instances.yourCBName.failure-rate-threshold=80
resilience4j.circuitbreaker.instances.yourCBName.sliding-window-type=COUNT_BASED
resilience4j.circuitbreaker.instances.yourCBName.sliding-window-size=5
resilience4j.circuitbreaker.instances.yourCBName.wait-duration-in-open-state=10000
resilience4j.circuitbreaker.instances.yourCBName.automatic-transition-from-open-to-half-open-enabled=true
spring.kafka.consumer.enable.auto.commit = false
spring.kafka.listener.ack-mode = MANUAL_IMMEDIATE
Also have a look at https://resilience4j.readme.io/docs/circuitbreaker

Answer 2

If you are using Spring Kafka, you could maybe use the pause and resume methods of the ConcurrentMessageListenerContainer class.
You can attach an EventListener to the CircuitBreaker which listens on state transitions and pauses or resumes processing of events. Inject the CircuitBreakerRegistry into you bean:
circuitBreakerRegistry.circuitBreaker("yourCBName").getEventPublisher().onStateTransition(
event -> {
switch (event.getStateTransition()) {
case CLOSED_TO_OPEN:
container.pause();
case OPEN_TO_HALF_OPEN:
container.resume();
case HALF_OPEN_TO_CLOSED:
container.resume();
case HALF_OPEN_TO_OPEN:
container.pause();
case CLOSED_TO_FORCED_OPEN:
container.pause();
case FORCED_OPEN_TO_CLOSED:
container.resume();
case FORCED_OPEN_TO_HALF_OPEN:
container.resume();
default:
}
}
);