Control enabling/disabling Kafka consumers in Spring Boot

Question

I have configured several Kafka consumers in Spring Boot. This is what the kafka.properties looks like (only listing config for one consumer here):

kafka.topics=
bootstrap.servers=
group.id=
enable.auto.commit=
auto.commit.interval.ms=
session.timeout.ms=
schema.registry.url=
auto.offset.reset=
kafka.enabled=

Here is the config:

@Configuration
@PropertySource({"classpath:kafka.properties"})
public class KafkaConsumerConfig {

    @Autowired
    private Environment env;

    @Bean
    public ConsumerFactory<String, String> pindropConsumerFactory() {
        Map<String, Object> dataRiverProps = new HashMap<>();

        dataRiverProps.put(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG, env.getProperty("bootstrap.servers"));
        dataRiverProps.put(ConsumerConfig.GROUP_ID_CONFIG, env.getProperty("group.id"));
        dataRiverProps.put(ConsumerConfig.ENABLE_AUTO_COMMIT_CONFIG, env.getProperty("enable.auto.commit"));
        dataRiverProps.put(ConsumerConfig.AUTO_COMMIT_INTERVAL_MS_CONFIG, env.getProperty("auto.commit.interval.ms"));
        dataRiverProps.put(ConsumerConfig.SESSION_TIMEOUT_MS_CONFIG, env.getProperty("session.timeout.ms"));

        dataRiverProps.put(ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG, StringDeserializer.class.getName());
        dataRiverProps.put(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG, StringDeserializer.class.getName());
        dataRiverProps.put(ConsumerConfig.AUTO_OFFSET_RESET_CONFIG, env.getProperty("auto.offset.reset"));

        return new DefaultKafkaConsumerFactory<>(dataRiverProps);
    }

    @Bean
    public ConcurrentKafkaListenerContainerFactory<String, String> kafkaListenerContainerFactory() {
        ConcurrentKafkaListenerContainerFactory<String, String> factory = new ConcurrentKafkaListenerContainerFactory<>();
        factory.setConsumerFactory(pindropConsumerFactory());
        return factory;
    }
}

And this is the consumer:

@Component
public class KafkaConsumer {

    @Autowired
    private MessageProcessor messageProcessor;


    @KafkaListener(topics = "#{'${kafka.topics}'.split(',')}", containerFactory = "kafkaListenerContainerFactory")
    public void consumeJson(String message) {
        // processing message
    }
}

Is there a way for me to use the prop "kafka.enabled" so that I can control the creation or maybe the message retrieval of this consumer? Thanks so much!

Answer 1

You can do it by using property autoStartup (true/false) in consumer like below -

@KafkaListener(id = "foo", topics = "Topic1", groupId = "group_id",
        containerFactory = "kafkaListenerContainerFactory",autoStartup = "${listen.auto.start:false}")
public void consume(String message) {
    //System.out.println("Consumed message: " + message);
}

Answer 2

To disable Kafka configuration you can, for example:

1. Annotate KafkaConsumerConfig with

   @ConditionalOnProperty(value = "kafka.enabled", matchIfMissing = true)

2. Remove @Component on KafkaConsumer class and define it as @Bean in KafkaConsumerConfig.

To control message retrieval in KafkaConsumer:

1. Just get property value inside KafkaConsumer @Value("kafka.enabled") private Boolean enabled;

2. And then use simple if in method annotated with @KafkaListener.