Kafka之enable.auto.commit使用解析

通过字面意思我们不难理解这是kafka的自动提交功能。

配置消费者(配置ENABLE_AUTO_COMMIT_CONFIG为 true 配置自动提交)

**enable.auto.commit **的默认值是 true；就是默认采用自动提交的机制。

**auto.commit.interval.ms 的默认值是 **5000，单位是毫秒。

此时我们配置消息消费后自动提交offset 位置

    @Bean
    public KafkaConsumer<String, String> kafkaConsumer() {
        Map<String, Object> config = new HashMap<>();
        config.put(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG, "127.0.0.1:9092");
        config.put(ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG, "org.apache.kafka.common.serialization.StringDeserializer");
        config.put(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG, "org.apache.kafka.common.serialization.StringDeserializer");
        config.put(ConsumerConfig.GROUP_ID_CONFIG, "groupId");
        config.put(ConsumerConfig.ENABLE_AUTO_COMMIT_CONFIG, true);
        KafkaConsumer<String, String> consumer = new KafkaConsumer<>(config);
        return consumer;
    }

配置消息监听

@Slf4j
@Component
public class PackageMessageConsumer {

    @Autowired
    KafkaConsumer<String, String> kafkaConsumer;
    @Autowired
    EventProcessMaster eventProcessMaster;

    @PostConstruct
    public void listenRealTimeGroup() {
        new Thread(() -> consumer()).start();
    }

 private void consumer() {
 List<String> topics = new ArrayList<>();
        topics.add("test-kafka-auto.commit");
        kafkaConsumer.subscribe(topics);
        while(true) {
            try {
                // 拉取消息时间间隔 ms
                ConsumerRecords<String, String> records = kafkaConsumer.poll(10);
                for (ConsumerRecord<String, String> record : records) {
                    String key = record.key();
                    Object content =  record.value();
                    eventProcessMaster.processRequest(new Event(record.topic(), key, content));
                }
            } catch (Exception e){
                log.error(e.getMessage());
            }
        }
    }
}

配置自动提交offset 位置之后，我们不必关心消息消费到了什么位置，当程序重启后，消息也不会重复消费；

配置消费者(配置ENABLE_AUTO_COMMIT_CONFIG为 false 配置手动提交)

手动提交顾名思义就是每次我们消费后，kafka不会手动更新offset 位置，同时 auto.commit.interval.ms 也就不被再考虑了。

    @Bean
    public KafkaConsumer<String, String> kafkaConsumer() {
        Map<String, Object> config = new HashMap<>();
        config.put(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG, "127.0.0.1:9092");
        config.put(ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG, "org.apache.kafka.common.serialization.StringDeserializer");
        config.put(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG, "org.apache.kafka.common.serialization.StringDeserializer");
        config.put(ConsumerConfig.GROUP_ID_CONFIG, "groupId");
        // 与自动提交的区别
        config.put(ConsumerConfig.ENABLE_AUTO_COMMIT_CONFIG, false);
        KafkaConsumer<String, String> consumer = new KafkaConsumer<>(config);
        return consumer;
    }

当我们设置成手动提交后，不修改其他代码会发现每次重启程序，kafka都会将我们没清理的所有数据都重新消费一遍，与我们需求的幂等性不符，将代码进行完善

    @Bean
    public KafkaConsumer<String, String> kafkaConsumer() {
        Map<String, Object> config = new HashMap<>();
        config.put(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG, "127.0.0.1:9092");
        config.put(ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG, "org.apache.kafka.common.serialization.StringDeserializer");
        config.put(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG, "org.apache.kafka.common.serialization.StringDeserializer");
        config.put(ConsumerConfig.GROUP_ID_CONFIG, "groupId");
        // 与自动提交的区别
        config.put(ConsumerConfig.AUTO_COMMIT_INTERVAL_MS_CONFIG, "100");// 自动提交时间间隔
        config.put(ConsumerConfig.ENABLE_AUTO_COMMIT_CONFIG, false);
        KafkaConsumer<String, String> consumer = new KafkaConsumer<>(config);
        return consumer;
    }

@Slf4j
@Component
public class DependPackageMessageConsumer {

 @Autowired
    KafkaConsumer<String, String> kafkaConsumer;
    @Autowired
    EventProcessMaster eventProcessMaster;

    @PostConstruct
    public void listenRealTimeGroup() {
        new Thread(() -> consumer()).start();
    }

 private void consumer() {
 List<String> topics = new ArrayList<>();
        topics.add("test-kafka-auto.commit");
        kafkaConsumer.subscribe(topics);
        while(true) {
            try {
                ConsumerRecords<String, String> records = kafkaConsumer.poll(10);
                for (ConsumerRecord<String, String> record : records) {
                    String key = record.key();
                    Object content =  record.value();
                    eventProcessMaster.processRequest(new Event(record.topic(), key, content));
                }
                // 手动提交 offset 位置
                kafkaConsumer.commitSync();
            } catch (Exception e){
                log.error(e.getMessage());
            }
        }
    }
}

加上手动确认后服务重启，每次都会从上次offset 确认的位置开始消费