Kafka consumer health check

Question

Is there a simple way to say if a consumer (created with spring boot and @KafkaListener) is operating normally? This includes - can access and poll a broker, has at least one pa

Answer 1

You can use the AdminClient to get the current group status...

@SpringBootApplication
public class So56134056Application {

    public static void main(String[] args) {
        SpringApplication.run(So56134056Application.class, args);
    }

    @Bean
    public NewTopic topic() {
        return new NewTopic("so56134056", 1, (short) 1);
    }

    @KafkaListener(id = "so56134056", topics = "so56134056")
    public void listen(String in) {
        System.out.println(in);
    }

    @Bean
    public ApplicationRunner runner(KafkaAdmin admin) {
        return args -> {
            try (AdminClient client = AdminClient.create(admin.getConfig())) {
                while (true) {
                    Map<String, ConsumerGroupDescription> map =
                            client.describeConsumerGroups(Collections.singletonList("so56134056")).all().get(10, TimeUnit.SECONDS);
                    System.out.println(map);
                    System.in.read();
                }
            }
        };
    }

}

{so56134056=(groupId=so56134056, isSimpleConsumerGroup=false, members=(memberId=consumer-2-32a80e0a-2b8d-4519-b71d-671117e7eaf8, clientId=consumer-2, host=/127.0.0.1, assignment=(topicPartitions=so56134056-0)), partitionAssignor=range, state=Stable, coordinator=localhost:9092 (id: 0 rack: null))}

We have been thinking about exposing getLastPollTime() to the listener container API.

getAssignedPartitions() has been available since 2.1.3.

Answer 2

I know that you haven't mentioned it in your post - but beware of adding items like this to a health check if you then deploy in AWS and use such a health check for your ELB scaling environment.

For example one scenario that can happen is that your app loses connectivity to Kafka - your health check turns RED - and then elastic beanstalks begins a process of killing and re-starting your instances (which will happen continually until your Kafka instances are available again). This could be costly!

There is also a more general philosophical question on whether health checks should 'cascade failures' or not e.g. kafka is down so app connected to kafka claims it is down, the next app in the chain also does the same, etc etc. This is often more normally implemented via circuit breakers which are designed to minimise slow calls destined for failure.