RabbitMQ延迟队列

1.  延迟队列的使用场景

• 延迟消费

  (a)未按时支付的订单，30分钟过期之后取消订单
  (b)给活跃度低的用户间隔N天推送消息
  (c)新注册用户1分钟后发送邮件

• 延迟重试

  消费者从队列里消费消息时失败了，但是想要延迟一段时间后自动重试（设想支付宝的支付回调是怎么实现的）

2.  实现延迟队列的方式有两种

1. 通过消息过期后进入死信交换器，再由交换器转发到延迟消费队列，实现延迟功能；
2. 使用rabbitmq-delayed-message-exchange插件实现延迟功能（注意： 延迟插件rabbitmq-delayed-message-exchange是在RabbitMQ 3.5.7及以上的版本才支持的，依赖Erlang/OPT 18.0及以上运行环境。）

 本文采用第二种延迟插件方式，安装过程见https://www.cnblogs.com/yangjiming/p/11024072.html

1.  配置队列

@Configuration
public class DelayRabbitConfig {

    public final static String QUEUE_NAME = "delayed.goods.order";
    public final static String EXCHANGE_NAME = "delayedExchange";
    public final static Long DELAY_TIME=5000L;
    @Bean
    public Queue delayQueue() {
        return new Queue(DelayRabbitConfig.QUEUE_NAME);
    }

    // 配置默认的交换机
    @Bean
    public CustomExchange delayedExchange() {
        Map<String, Object> args = new HashMap<>(16);
        args.put("x-delayed-type", "direct");
        //参数二为类型：必须是x-delayed-message
        return new CustomExchange(DelayRabbitConfig.EXCHANGE_NAME, "x-delayed-message",true, false, args);
    }

    // 绑定队列到交换器
    @Bean
    public Binding binding() {
        return BindingBuilder
                .bind(delayQueue())
                .to((delayedExchange()))
                .with(DelayRabbitConfig.QUEUE_NAME)
                .noargs();
    }
}

2.  发送消息

@Component
public class DelaySender {
    @Autowired
    private AmqpTemplate rabbitTemplate;

    public void sendMsg(String msg) {
        LocalDateTime localDateTime = LocalDateTime.now();

        rabbitTemplate.convertAndSend(DelayRabbitConfig.EXCHANGE_NAME,
                DelayRabbitConfig.QUEUE_NAME,
                "helo "+msg+" 发送时间"+localDateTime,
                message ->  {
                    message.getMessageProperties().setHeader("x-delay", DelayRabbitConfig.DELAY_TIME);
                    return message;
                }
        );
    }
}

3. 消费消息

@Component
@RabbitListener(queues = DelayRabbitConfig.QUEUE_NAME)
public class DelayReceiver {

    @RabbitHandler
    public void helloConsumer(String content) throws IOException {
        LocalDateTime localDateTime = LocalDateTime.now();
        System.out.println("接收时间:" + localDateTime);
        System.out.println("消息内容：" + content);
    }
}

4.  测试类

@RunWith(SpringRunner.class)
@SpringBootTest
public class DelayTest {

    @Autowired
    private DelaySender delaySender;
    @Test
    public void hello() throws Exception {
        delaySender.sendMsg("麦粒肿");
        Thread.sleep(5000);
    }
}