RocketMQ消费端

今天要来跟大家学习怎样使用RocketMQ来进行消息的消费

先简单创建个Maven项目使用

• 添加依赖

<dependency>
    <groupId>org.apache.rocketmq</groupId>
    <artifactId>rocketmq-client</artifactId>
    <version>4.9.2</version>
</dependency>

• 启动消费者

  package mq.consumer;
  
  import org.apache.rocketmq.client.consumer.DefaultMQPushConsumer;
  import org.apache.rocketmq.client.consumer.listener.ConsumeConcurrentlyContext;
  import org.apache.rocketmq.client.consumer.listener.ConsumeConcurrentlyStatus;
  import org.apache.rocketmq.client.consumer.listener.MessageListenerConcurrently;
  import org.apache.rocketmq.client.exception.MQClientException;
  import org.apache.rocketmq.common.message.MessageExt;
  import org.apache.rocketmq.common.protocol.heartbeat.MessageModel;
  
  import java.util.List;
  
  public class BroadcastConsumer {
      public static void main(String[] args) throws MQClientException {
          //创建一个push模式的消费组
          DefaultMQPushConsumer pushConsumer = new DefaultMQPushConsumer("pushConsumer");
          pushConsumer.setNamesrvAddr("localhost:9876");
          //集群模式
          pushConsumer.setMessageModel(MessageModel.CLUSTERING);
          //  订阅的topic tag
          pushConsumer.subscribe("topic_test01","Tag1 || Tag2");
  
          pushConsumer.registerMessageListener(new MessageListenerConcurrently() {
              @Override
              public ConsumeConcurrentlyStatus consumeMessage(List<MessageExt> msgs, ConsumeConcurrentlyContext context) {
                  System.out.printf(Thread.currentThread().getName() + " Receive New Messages: " + msgs + "%n");
                  return ConsumeConcurrentlyStatus.CONSUME_SUCCESS;
              }
          });
          pushConsumer.start();
          System.out.printf("Broadcast Consumer Started.%n");
  
      }
  
  

• 启动生产者

  package mq.producer;
  
  import org.apache.rocketmq.client.exception.MQBrokerException;
  import org.apache.rocketmq.client.exception.MQClientException;
  import org.apache.rocketmq.client.producer.DefaultMQProducer;
  import org.apache.rocketmq.client.producer.SendResult;
  import org.apache.rocketmq.common.message.Message;
  import org.apache.rocketmq.remoting.common.RemotingHelper;
  import org.apache.rocketmq.remoting.exception.RemotingException;
  
  import java.io.UnsupportedEncodingException;
  
  public class SyncProducerV2 {
      /**
       * 同步消息发送
       *
       * @param args
       * @throws MQClientException
       * @throws MQBrokerException
       * @throws RemotingException
       * @throws InterruptedException
       * @throws UnsupportedEncodingException
       */
      public static void main(String[] args) throws MQClientException, MQBrokerException, RemotingException, InterruptedException, UnsupportedEncodingException {
          System.out.println("SyncProducer start......");
          DefaultMQProducer defaultMQProducer = new DefaultMQProducer("pg_sync_01");
          defaultMQProducer.setNamesrvAddr("localhost:9876");
          defaultMQProducer.start();
          for (int i = 0; i < 10; i++) {
              send(defaultMQProducer, i, i % 3);
          }
          defaultMQProducer.shutdown();
          System.out.println("SyncProducer end......");
  
      }
  
      private static void send(DefaultMQProducer defaultMQProducer, Integer i, int tag) throws MQClientException, RemotingException, MQBrokerException, InterruptedException, UnsupportedEncodingException {
          SendResult sendResult = defaultMQProducer.send(new Message("topic_test01", "Tag" + tag, ("hello this is sync message_" + i + "!").getBytes(RemotingHelper.DEFAULT_CHARSET)));
          System.out.println(sendResult);
      }
  }
  

• 消费者消费

可以看到消费了Tag为Tag1、Tag2的消息

其它Tag会被过滤掉

消费分类

RocketMQ的消费模式分为两种：BROADCASTING（广播）和CLUSTERING（集群）

那这两种模式有什么区别呢？

• 广播：相同消费组下的实例会重复消费同一个Topic的消息，可以理解为大家做同样的工作，消费进度存储在客户端，有可能会导致部分消息没有被消费
• 集群：相同消费组下的实例会负载均衡地消费同一个Topic的消息，可以理解为分工合作，消费进度存储在Broker端

所以大部分系统都会使用集群模式去消费信息，毕竟可以水平拓展消费者来承受更大的消费压力

广播模式相对来说使用比较少，一般都是一些消息通知同步的场景，想同步刷新缓存等