Spring Kafka 事务导致生产者每条消息偏移量增加 2

Question

我在使用 Spring(boot) Kafka 的微服务中有一个消费-转换-生产工作流程。我需要实现 Kafka 事务提供的一次性语义。 这是下面的代码sn-p：

配置

@Bean
public ProducerFactory<String, String> producerFactory() {
    Map<String, Object> props = new HashMap<>();
    props.put(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG, bootstrapServers);
    props.put(ProducerConfig.KEY_SERIALIZER_CLASS_CONFIG, StringSerializer.class);
    props.put(ProducerConfig.VALUE_SERIALIZER_CLASS_CONFIG, StringSerializer.class);
    props.put(ProducerConfig.ENABLE_IDEMPOTENCE_CONFIG, true);
    props.put(ProducerConfig.MAX_REQUEST_SIZE_CONFIG, 1024 * 1024);
    DefaultKafkaProducerFactory<String, String> defaultKafkaProducerFactory = new DefaultKafkaProducerFactory<>(props);
    defaultKafkaProducerFactory.setTransactionIdPrefix("kafka-trx-");
    return defaultKafkaProducerFactory;
}

@Bean
public ConsumerFactory<String, String> consumerFactory() {
    Map<String, Object> props = new HashMap<>();
    props.put(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG, bootstrapServers);
    props.put(ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG, StringDeserializer.class);
    props.put(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG, StringDeserializer.class);
    props.put(ConsumerConfig.MAX_POLL_RECORDS_CONFIG, 5000);
    props.put(ConsumerConfig.AUTO_OFFSET_RESET_CONFIG, "earliest");
    props.put(ConsumerConfig.ENABLE_AUTO_COMMIT_CONFIG, false);
    props.put(ConsumerConfig.ISOLATION_LEVEL_CONFIG, "read_committed");
    return new DefaultKafkaConsumerFactory<>(props);
}

@Bean
public KafkaTemplate<String, String> kafkaTemplate() {
    return new KafkaTemplate<>(producerFactory());
}

@Bean
public KafkaTransactionManager<String, String> kafkaTransactionManager() {
    return new KafkaTransactionManager<>(producerFactory());
}

@Bean
@Qualifier("chainedKafkaTransactionManager")
public ChainedKafkaTransactionManager<String, Object> chainedKafkaTransactionManager(KafkaTransactionManager<String, String> kafkaTransactionManager) {
    return new ChainedKafkaTransactionManager<>(kafkaTransactionManager);
}

@Bean
public ConcurrentKafkaListenerContainerFactory<?, ?> concurrentKafkaListenerContainerFactory(ChainedKafkaTransactionManager<String, Object> chainedKafkaTransactionManager) {
    ConcurrentKafkaListenerContainerFactory<String, String> concurrentKafkaListenerContainerFactory = new ConcurrentKafkaListenerContainerFactory<>();
    concurrentKafkaListenerContainerFactory.setConsumerFactory(consumerFactory());
    concurrentKafkaListenerContainerFactory.setBatchListener(true);
    concurrentKafkaListenerContainerFactory.setConcurrency(nexusConsumerConcurrency);
    //concurrentKafkaListenerContainerFactory.setReplyTemplate(kafkaTemplate());
    concurrentKafkaListenerContainerFactory.getContainerProperties().setAckMode(AbstractMessageListenerContainer.AckMode.BATCH);
    concurrentKafkaListenerContainerFactory.getContainerProperties().setTransactionManager(chainedKafkaTransactionManager);
    return concurrentKafkaListenerContainerFactory;
}

听众

@KafkaListener(topics = "${kafka.xxx.consumerTopic}", groupId = "${kafka.xxx.consumerGroup}", containerFactory = "concurrentKafkaListenerContainerFactory")
public void listen(@Payload List<String> msgs, @Header(KafkaHeaders.RECEIVED_PARTITION_ID) List<Integer> partitions, @Header(KafkaHeaders.OFFSET) List<Integer> offsets) {

    int i = -1;
    for (String msg : msgs) {
        ++i;
        LOGGER.debug("partition={}; offset={}; msg={}", partitions.get(i), offsets.get(i), msg);
        String json = transform(msg);
        kafkaTemplate.executeInTransaction(kt -> kt.send(producerTopic, json));
    }
}

但是在产品环境中，我遇到了一个奇怪的问题。生产者发送的每条消息，偏移量增加 2，消费者不提交消费偏移量。

主题 1 的消费者偏移量

Topic1 消费者详情

制作主题2

但是，生产者发送的消息数与消费者发送的消息数相同。生产者的下游可以连续接收来自topic2的消息。日志中没有发现错误或异常。

我想知道为什么 consumer-transform-produce 工作流程看起来没问题（也可以保证完全一次 scemantics），但是没有提交消耗的偏移量，并且每个 msg 生成的 msg 偏移增量是 2 而不是 1。

如何解决？谢谢！

Answer 1

这就是它的设计方式。 Kafka 日志是不可变的，因此在事务结束时使用一个额外的“槽”来指示事务是提交还是回滚。这允许具有read_committed 隔离级别的消费者跳过回滚事务。

如果您在一个事务中发布 10 条记录，您将看到偏移量增加 11。如果您只发布一条，它将增加 2。

如果您希望发布参与消费者启动的事务（仅一次），则不应使用executeInTransaction；这将开始一个新的交易。

/**
 * Execute some arbitrary operation(s) on the operations and return the result.
 * The operations are invoked within a local transaction and do not participate
 * in a global transaction (if present).
 * @param callback the callback.
 * @param <T> the result type.
 * @return the result.
 * @since 1.1
 */
<T> T executeInTransaction(OperationsCallback<K, V, T> callback);

我不明白为什么消费者偏移量仍不会发送到消费者启动的事务。您应该打开 DEBUG 日志记录以查看发生了什么（如果在您修复模板代码后仍然发生）。

编辑

监听器退出时，监听器容器将消耗的偏移量（+1）发送给事务；打开提交日志，你会看到它...

@SpringBootApplication
public class So59152915Application {

    public static void main(String[] args) {
        SpringApplication.run(So59152915Application.class, args);
    }

    @Autowired
    private KafkaTemplate<String, String> template;

    @KafkaListener(id = "foo", topics = "so59152915-1", clientIdPrefix = "so59152915")
    public void listen1(String in, @Header(KafkaHeaders.OFFSET) long offset) throws InterruptedException {
        System.out.println(in + "@" + offset);
        this.template.send("so59152915-2", in.toUpperCase());
        Thread.sleep(2000);
    }

    @KafkaListener(id = "bar", topics = "so59152915-2")
    public void listen2(String in) {
        System.out.println(in);
    }

    @Bean
    public NewTopic topic1() {
        return new NewTopic("so59152915-1", 1, (short) 1);
    }

    @Bean
    public NewTopic topic2() {
        return new NewTopic("so59152915-2", 1, (short) 1);
    }

    @Bean
    public ApplicationRunner runner(KafkaListenerEndpointRegistry registry) {
        return args -> {
            this.template.executeInTransaction(t -> {
                IntStream.range(0, 11).forEach(i -> t.send("so59152915-1", "foo" + i));
                try {
                    System.out.println("Hit enter to commit sends");
                    System.in.read();
                }
                catch (IOException e) {
                    e.printStackTrace();
                }
                return null;
            });
        };
    }

}

@Component
class Configurer {

    Configurer(ConcurrentKafkaListenerContainerFactory<?, ?> factory) {
        factory.getContainerProperties().setCommitLogLevel(Level.INFO);
    }

}

和

spring.kafka.producer.transaction-id-prefix=tx-
spring.kafka.consumer.properties.isolation.level=read_committed
spring.kafka.consumer.auto-offset-reset=earliest

和

foo0@56
2019-12-04 10:07:18.551  INFO 55430 --- [      foo-0-C-1] essageListenerContainer$ListenerConsumer : Sending offsets to transaction: {so59152915-1-0=OffsetAndMetadata{offset=57, leaderEpoch=null, metadata=''}}
foo1@57
FOO0
2019-12-04 10:07:18.558  INFO 55430 --- [      bar-0-C-1] essageListenerContainer$ListenerConsumer : Sending offsets to transaction: {so59152915-2-0=OffsetAndMetadata{offset=63, leaderEpoch=null, metadata=''}}
2019-12-04 10:07:20.562  INFO 55430 --- [      foo-0-C-1] essageListenerContainer$ListenerConsumer : Sending offsets to transaction: {so59152915-1-0=OffsetAndMetadata{offset=58, leaderEpoch=null, metadata=''}}
foo2@58

Answer 2

请注意您的自动提交设置。如我所见，您将其设置为 false：

props.put(ConsumerConfig.ENABLE_AUTO_COMMIT_CONFIG, false);

因此，在这种情况下，您需要“手动”提交或将自动提交设置为 true。