如何在Kafka听者法中寻找一个特定的偏移量？

Question

public class Listen implements ConsumerSeekAware 
{
 @Override
    public void registerSeekCallback(ConsumerSeekCallback callback)

    {
//      fetching offset from a database 
        Integer offset = offsetService.getOffset();
        callback.seek("topic-name",0,offset);

    }
 @KafkaListener(topics = "topic-name", groupId = "group")
  public void listen(ConsumerRecord record Acknowledgment acknowledgment) throws Exception 
  {
//    processing the record 

      acknowledgment.acknowledge();    //manually commiting the record
//    committing the offset to MySQL database
  }
}

@KafkaListener(topics = "topic-name", groupId = "group")
  public void listen(ConsumerRecord record Acknowledgment acknowledgment, 
  @Header(KafkaHeaders.CONSUMER) Consumer<?, ?> consumer)) throws Exception {
       // seeking old offset stored in database (which is 11 )
        consumer.seek(partition,offsetService.getOffset());
        log.info("record offset is {} and value is {}" , record.offset(),record.value() );
        acknowledgment.acknowledge();
}

Answer 1

这个答案有几种技巧。

请记住，在使用者上执行seek直到下一轮轮询才会生效（在上一轮轮询中获取的任何记录都将首先发送给使用者）。

编辑

@SpringBootApplication
public class So63429201Application {

    public static void main(String[] args) {
        SpringApplication.run(So63429201Application.class, args).close();
    }

    @Bean
    public ApplicationRunner runner(KafkaTemplate<String, String> template, Listener listener) {
        return args -> {
            IntStream.range(0, 10).forEach(i -> template.send("so63429201", i % 3,  null, "foo" + i));
            Thread.sleep(8000);
            listener.seekToTime(System.currentTimeMillis() - 11000);
            Thread.sleep(8000);
            listener.seekToOffset(new TopicPartition("so63429201", 0), 11);
            Thread.sleep(8000);
        };
    }


    @Bean
    public NewTopic topic() {
        return TopicBuilder.name("so63429201").partitions(3).replicas(1).build();
    }

}

@Component
class Listener extends AbstractConsumerSeekAware {

    @KafkaListener(id = "so63429201", topics = "so63429201", concurrency = "2")
    public void listen(String in) {
        System.out.println(in);
    }

    @Override
    public void onPartitionsAssigned(Map<TopicPartition, Long> assignments, ConsumerSeekCallback callback) {
        System.out.println(assignments);
        super.onPartitionsAssigned(assignments, callback);
        callback.seekToBeginning(assignments.keySet());
    }

    public void seekToTime(long time) {
        getSeekCallbacks().forEach((tp, callback) -> callback.seekToTimestamp(tp.topic(), tp.partition(), time));
    }

    public void seekToOffset(TopicPartition tp, long offset) {
        getSeekCallbackFor(tp).seek(tp.topic(), tp.partition(), offset);
    }

}