Hooks in Kafka Listener

Question

Is there any sort of hooks available before / after kafka listen a message ?

Use case : MDC co-relation id has to be set for to perform the log traceability

What I am looking for ? A before/after call back method so that MDC co-relation id can be set on entry and eventually clean MDC upon exit.

Edited Scenario: I am getting co-relation id as a part of Kafka Headers and I want to set the same in MDC as soon as I receive a message in Kafka Listener

Appreciated for help

Answer 1

You can add an around advice to your listener bean...

@SpringBootApplication
public class So59854374Application {

    public static void main(String[] args) {
        SpringApplication.run(So59854374Application.class, args);
    }

    @Bean
    public static BeanPostProcessor bpp() { // static is important
        return new BeanPostProcessor() {

            @Override
            public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
                if (bean instanceof MyListener) {
                    ProxyFactoryBean pfb = new ProxyFactoryBean();
                    pfb.setTarget(bean);
                    pfb.addAdvice(new MethodInterceptor() {

                        @Override
                        public Object invoke(MethodInvocation invocation) throws Throwable {
                            try {
                                System.out.println("Before");
                                return invocation.proceed();
                            }
                            finally {
                                System.out.println("After");
                            }
                        }

                    });
                    return pfb.getObject();
                }
                return bean;
            }

        };
    }

    @Bean
    public NewTopic topic() {
        return TopicBuilder.name("so59854374").partitions(1).replicas(1).build();
    }

    @Bean
    public ApplicationRunner runner(KafkaTemplate<String, String> template) {
        return args -> template.send("so59854374", "foo");
    }

}

@Component
class MyListener {

    @KafkaListener(id = "so59854374", topics = "so59854374")
    public void listen(String in) {
        System.out.println(in);
    }

}

and

Before
foo
After

EDIT

If you add @Header("myMdcHeader") byte[] mdc as an additional parameter to your kafka listener method, you can use getArguments()[1] on the invocation.

Another solution is to add a RecordInterceptor to the listener container factory, which allows you to access the raw ConsumerRecord before it is passed to the listener adapter.

/**
 * An interceptor for {@link ConsumerRecord} invoked by the listener
 * container before invoking the listener.
 *
 * @param <K> the key type.
 * @param <V> the value type.
 *
 * @author Gary Russell
 * @since 2.2.7
 *
 */
@FunctionalInterface
public interface RecordInterceptor<K, V> {

    /**
     * Perform some action on the record or return a different one.
     * If null is returned the record will be skipped.
     * @param record the record.
     * @return the record or null.
     */
    @Nullable
    ConsumerRecord<K, V> intercept(ConsumerRecord<K, V> record);

}

/**
 * Set an interceptor to be called before calling the listener.
 * Does not apply to batch listeners.
 * @param recordInterceptor the interceptor.
 * @since 2.2.7
 */
public void setRecordInterceptor(RecordInterceptor<K, V> recordInterceptor) {
    this.recordInterceptor = recordInterceptor;
}

If you are using a batch listener, Kafka provides a ConsumerInterceptor.