RabbitMQ死信队列和备份交换器

1.引言

死信交换机(Dead-Letter-Exchange):当消息在一个队列中由于过期、被拒绝等原因变成死信 (dead message) 之后,它能被重新被发送到另一个交换器中,这个交换器就是死信交换机,绑定死信交换机的队列就称之为死信队列。

判断一个消息是否是死信消息(Dead Message)的依据:

a. 消息被拒绝(Basic.Reject或Basic.Nack)并且设置 requeue 参数的值为 false;
b. 消息过期; 消息过期时间设置主要有两种方式:

1.设置队列的过期时间,这样该队列中所有的消息都存在相同的过期时间(在队列申明的时候使用 x-message-ttl 参数,单位为 毫秒);
2.单独设置某个消息的过期时间,每条消息的过期时间都不一样;(设置消息属性的 expiration 参数的值,单位为 毫秒); 
3.如果同时使用了两种方式设置过期时间,以两者之间较小的那个数值为准;

c. 队列已满(队列满了,无法再添加消息到mq中);

使用方法:申明队列的时候设置 x-dead-letter-exchange 参数

备份交换器(alternate-exchange):未被正确路由的消息将会经过此交换器

使用方法:申明交换器的时候设置 alternate-exchange 参数

2.案例模拟

下面通过一个简单的示例说明在RabbitMQ中死信队列和备份交换机的使用方法。

2.1.示意图

RabbitMQ死信队列和备份交换器_第1张图片

2.2.配置文件

RabbitMQ配置信息,绑定交换器、队列、路由键设置

package com.bruceliu.config;


import org.springframework.amqp.core.*;
import org.springframework.context.annotation.Bean;
import org.springframework.stereotype.Component;

import java.util.HashMap;
import java.util.Map;

/**
 * @Description: RabbitMQ配置信息,绑定交换器、队列、路由键设置
 * @author: weishihuai
 * @Date: 2019/6/27 15:38
 * 

* 说明: *

* 死信交换机(Dead-Letter-Exchange): 当消息变成一个死信之后,如果这个消息所在的队列存在x-dead-letter-exchange参数,那么它会被发送到x-dead-letter-exchange对应值的交换器上 *

* 使用方法:申明队列的时候设置 x-dead-letter-exchange 参数 *

* 判断一个消息是否是死信消息(Dead Message)的依据: * a. 消息被拒绝(Basic.Reject或Basic.Nack)并且设置 requeue 参数的值为 false; * b. 消息过期; 消息过期时间设置主要有两种方式: * 1.设置队列的过期时间,这样该队列中所有的消息都存在相同的过期时间(在队列申明的时候使用 x-message-ttl 参数,单位为 毫秒) * 2.单独设置某个消息的过期时间,每条消息的过期时间都不一样;(设置消息属性的 expiration 参数的值,单位为 毫秒) * 3.如果同时使用了两种方式设置过期时间,以两者之间较小的那个数值为准; * c. 队列已满(队列满了,无法再添加数据到mq中); *

* 备份交换器(alternate-exchange):未被正确路由的消息将会经过此交换器 * 使用方法:申明交换器的时候设置 alternate-exchange 参数 */ /** * @author bruceliu * @create 2019-11-03 17:41 * @description */ @Component public class RabbitMQConfig { //没有被正确路由的消息 备份队列 private static final String MESSAGE_BAK_QUEUE_NAME = "un_routing_queue_name"; //没有被正确路由的消息 备份交换机 private static final String MESSAGE_BAK_EXCHANGE_NAME = "un_routing_exchange_name"; //死信队列 private static final String DEAD_LETTERS_QUEUE_NAME = "dead_letters_queue_name"; //死信交换机 private static final String DEAD_LETTERS_EXCHANGE_NAME = "dead_letters_exchange_name"; //目标队列 private static final String QUEUE_NAME = "test_dlx_queue_name"; //目标消息交换机 private static final String EXCHANGE_NAME = "test_dlx_exchange_name"; //ROUTING_KEY private static final String ROUTING_KEY = "user.add"; /** * 声明备份队列、备份交换机、绑定队列到备份交换机 * 建议使用FanoutExchange广播式交换机 */ @Bean public Queue msgBakQueue() { return new Queue(MESSAGE_BAK_QUEUE_NAME); } @Bean public FanoutExchange msgBakExchange() { return new FanoutExchange(MESSAGE_BAK_EXCHANGE_NAME); } @Bean public Binding msgBakBinding() { return BindingBuilder.bind(msgBakQueue()).to(msgBakExchange()); } /** * 声明死信队列、死信交换机、绑定队列到死信交换机 * 建议使用FanoutExchange广播式交换机 */ @Bean public Queue deadLettersQueue() { return new Queue(DEAD_LETTERS_QUEUE_NAME); } @Bean public FanoutExchange deadLettersExchange() { return new FanoutExchange(DEAD_LETTERS_EXCHANGE_NAME); } @Bean public Binding deadLettersBinding() { return BindingBuilder.bind(deadLettersQueue()).to(deadLettersExchange()); } /** * 声明普通队列,并指定相应的备份交换机、死信交换机 */ @Bean public Queue queue() { Map<String, Object> arguments = new HashMap<>(10); //指定死信发送的Exchange arguments.put("x-dead-letter-exchange", DEAD_LETTERS_EXCHANGE_NAME); return new Queue(QUEUE_NAME, true, false, false, arguments); } @Bean public Exchange exchange() { Map<String, Object> arguments = new HashMap<>(10); //声明备份交换机 arguments.put("alternate-exchange", MESSAGE_BAK_EXCHANGE_NAME); return new DirectExchange(EXCHANGE_NAME, true, false, arguments); } @Bean public Binding binding() { return BindingBuilder.bind(queue()).to(exchange()).with(ROUTING_KEY).noargs(); } }

2.3.生产者

package com.bruceliu.producer;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.amqp.rabbit.connection.CorrelationData;
import org.springframework.amqp.rabbit.core.RabbitTemplate;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

import java.util.UUID;

/**
 * @author bruceliu
 * @create 2019-11-03 17:42
 * @description
 */
@Component
public class Producer {

    private static final Logger logger = LoggerFactory.getLogger(Producer.class);
    private static final String EXCHANGE_NAME = "test_dlx_exchange_name";
    private static final String ROUTING_KEY = "user.add";
    private static final String UN_ROUTING_KEY = "user.delete";

    @Autowired
    private RabbitTemplate rabbitTemplate;

    public void sendMessage() {
        // 发送10条能够正确被路由的消息
        for (int i = 1; i <= 10; i++) {
            String message = "发送第" + i + "条消息.";
            rabbitTemplate.convertAndSend(EXCHANGE_NAME, ROUTING_KEY, message, new CorrelationData(UUID.randomUUID().toString()));
            logger.info("【发送了一条能够正确被路由的消息】,exchange:[{}],routingKey:[{}],message:[{}]", EXCHANGE_NAME, ROUTING_KEY, message);
        }

        // 发送两条不能正确被路由的消息,该消息将会被转发到我们指定的备份交换器中
        for (int i = 1; i <= 2; i++) {
            String message = "不能正确被路由的消息" + i;
            rabbitTemplate.convertAndSend(EXCHANGE_NAME, UN_ROUTING_KEY, message, new CorrelationData(UUID.randomUUID().toString()));
            logger.info("【发送了第一条不能正确被路由的消息】,exchange:[{}],routingKey:[{}],message:[{}]", EXCHANGE_NAME, UN_ROUTING_KEY, message);
        }
    }

}

2.4.回调

自定义消息发送确认的回调

package com.bruceliu.callback;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.amqp.rabbit.connection.CorrelationData;
import org.springframework.amqp.rabbit.core.RabbitTemplate;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

import javax.annotation.PostConstruct;

/**
 * @author bruceliu
 * @create 2019-11-03 17:44
 * @description
 */
@Component
public class CustomConfirmCallback implements RabbitTemplate.ConfirmCallback {
    private static final Logger logger = LoggerFactory.getLogger(CustomConfirmCallback.class);

    @Autowired
    private RabbitTemplate rabbitTemplate;

    /**
     * PostConstruct: 用于在依赖关系注入完成之后需要执行的方法上,以执行任何初始化.
     */
    @PostConstruct
    public void init() {
        //指定 ConfirmCallback
        rabbitTemplate.setConfirmCallback(this);
    }

    @Override
    public void confirm(CorrelationData correlationData, boolean isSendSuccess, String error) {
        logger.info("(start)生产者消息确认=========================");
        if (!isSendSuccess) {
            logger.info("消息可能未到达rabbitmq服务器");
        }
        logger.info("(end)生产者消息确认=========================");
    }

}

2.5 消费者

package com.bruceliu.consumer;

import com.rabbitmq.client.Channel;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.amqp.core.Message;
import org.springframework.amqp.rabbit.annotation.RabbitListener;
import org.springframework.stereotype.Component;

import java.io.IOException;
import java.util.Random;

/**
 * @author bruceliu
 * @create 2019-11-03 17:56
 * @description
 */
@Component
public class Consumer {

    private static final Logger logger = LoggerFactory.getLogger(Consumer.class);

    @RabbitListener(queues = "test_dlx_queue_name")
    public void receiveMessage(String receiveMessage, Message message, Channel channel) {
        try {
            logger.info("【Consumer】接收到消息:[{}]", receiveMessage);
            //这里模拟随机拒绝一些消息到死信队列中
            if (new Random().nextInt(10) < 5) {
                logger.info("【Consumer】拒绝一条信息:[{}],该消息将会被转发到死信交换器中", receiveMessage);
                channel.basicNack(message.getMessageProperties().getDeliveryTag(), false, false);
            } else {
                channel.basicAck(message.getMessageProperties().getDeliveryTag(), false);
            }
        } catch (Exception e) {
            logger.info("【Consumer】接消息后的处理发生异常", e);
            try {
                channel.basicAck(message.getMessageProperties().getDeliveryTag(), false);
            } catch (IOException e1) {
                logger.error("手动确认消息异常.", e1);
            }
        }
    }

}

2.6.配置文件

server:
  port: 7777
spring:
  application:
    name: mq-dead-letter-exchange-producer
  rabbitmq:
    host: 127.0.0.1
    virtual-host: /
    username: guest
    password: guest
    port: 5672
    #消息发送确认回调
    publisher-confirms: true
    listener:
      simple:
        acknowledge-mode: manual
        retry:
          enabled: true
        prefetch: 1
        auto-startup: true
        default-requeue-rejected: false
    # publisher-returns: true
    template:
      #当mandatory设置为true时,如果exchange根据自身类型和消息routingKey无法找到一个合适的queue存储消息,那么broker会调用basic.return方法将消息返还给生产者;
      #当mandatory设置为false时,出现上述情况broker会直接将消息丢弃;
      #通俗的讲,mandatory标志告诉broker代理服务器至少将消息route到一个队列中,否则就将消息return给发送者;
      mandatory: true
    connection-timeout: 10000

2.7.测试用例

package com.bruceliu.test;

import com.bruceliu.producer.Producer;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;

/**
 * @author bruceliu
 * @create 2019-11-03 17:47
 * @description
 */
@RunWith(SpringRunner.class)
@SpringBootTest
public class SpringbootRabbitmqDeadLetterExchangeApplicationTests {

    @Autowired
    private Producer producer;

    @Test
    public void contextLoads() {
        producer.sendMessage();
    }

}

2.8.运行结果

生产者:

2019-11-03 17:59:46.026  INFO 33100 --- [           main] o.s.a.r.c.CachingConnectionFactory       : Attempting to connect to: [127.0.0.1:5672]
2019-11-03 17:59:46.073  INFO 33100 --- [           main] o.s.a.r.c.CachingConnectionFactory       : Created new connection: rabbitConnectionFactory#6134ac4a:0/SimpleConnection@255e5e2e [delegate=amqp://guest@127.0.0.1:5672/, localPort= 54334]
2019-11-03 17:59:46.120  INFO 33100 --- [           main] com.bruceliu.producer.Producer           : 【发送了一条能够正确被路由的消息】,exchange:[test_dlx_exchange_name],routingKey:[user.add],message:[发送第1条消息.]
2019-11-03 17:59:46.120  INFO 33100 --- [           main] com.bruceliu.producer.Producer           : 【发送了一条能够正确被路由的消息】,exchange:[test_dlx_exchange_name],routingKey:[user.add],message:[发送第2条消息.]
2019-11-03 17:59:46.120  INFO 33100 --- [           main] com.bruceliu.producer.Producer           : 【发送了一条能够正确被路由的消息】,exchange:[test_dlx_exchange_name],routingKey:[user.add],message:[发送第3条消息.]
2019-11-03 17:59:46.120  INFO 33100 --- [           main] com.bruceliu.producer.Producer           : 【发送了一条能够正确被路由的消息】,exchange:[test_dlx_exchange_name],routingKey:[user.add],message:[发送第4条消息.]
2019-11-03 17:59:46.120  INFO 33100 --- [           main] com.bruceliu.producer.Producer           : 【发送了一条能够正确被路由的消息】,exchange:[test_dlx_exchange_name],routingKey:[user.add],message:[发送第5条消息.]
2019-11-03 17:59:46.136  INFO 33100 --- [           main] com.bruceliu.producer.Producer           : 【发送了一条能够正确被路由的消息】,exchange:[test_dlx_exchange_name],routingKey:[user.add],message:[发送第6条消息.]
2019-11-03 17:59:46.136  INFO 33100 --- [           main] com.bruceliu.producer.Producer           : 【发送了一条能够正确被路由的消息】,exchange:[test_dlx_exchange_name],routingKey:[user.add],message:[发送第7条消息.]
2019-11-03 17:59:46.151  INFO 33100 --- [ 127.0.0.1:5672] c.b.callback.CustomConfirmCallback       : (start)生产者消息确认=========================
2019-11-03 17:59:46.151  INFO 33100 --- [ 127.0.0.1:5672] c.b.callback.CustomConfirmCallback       : (end)生产者消息确认=========================
2019-11-03 17:59:46.151  INFO 33100 --- [ 127.0.0.1:5672] c.b.callback.CustomConfirmCallback       : (start)生产者消息确认=========================
2019-11-03 17:59:46.151  INFO 33100 --- [ 127.0.0.1:5672] c.b.callback.CustomConfirmCallback       : (end)生产者消息确认=========================
2019-11-03 17:59:46.151  INFO 33100 --- [ 127.0.0.1:5672] c.b.callback.CustomConfirmCallback       : (start)生产者消息确认=========================
2019-11-03 17:59:46.151  INFO 33100 --- [ 127.0.0.1:5672] c.b.callback.CustomConfirmCallback       : (end)生产者消息确认=========================
2019-11-03 17:59:46.151  INFO 33100 --- [ 127.0.0.1:5672] c.b.callback.CustomConfirmCallback       : (start)生产者消息确认=========================
2019-11-03 17:59:46.151  INFO 33100 --- [ 127.0.0.1:5672] c.b.callback.CustomConfirmCallback       : (end)生产者消息确认=========================
2019-11-03 17:59:46.151  INFO 33100 --- [ 127.0.0.1:5672] c.b.callback.CustomConfirmCallback       : (start)生产者消息确认=========================
2019-11-03 17:59:46.151  INFO 33100 --- [ 127.0.0.1:5672] c.b.callback.CustomConfirmCallback       : (end)生产者消息确认=========================
2019-11-03 17:59:46.151  INFO 33100 --- [ 127.0.0.1:5672] c.b.callback.CustomConfirmCallback       : (start)生产者消息确认=========================
2019-11-03 17:59:46.151  INFO 33100 --- [ 127.0.0.1:5672] c.b.callback.CustomConfirmCallback       : (end)生产者消息确认=========================
2019-11-03 17:59:46.151  INFO 33100 --- [           main] com.bruceliu.producer.Producer           : 【发送了一条能够正确被路由的消息】,exchange:[test_dlx_exchange_name],routingKey:[user.add],message:[发送第8条消息.]
2019-11-03 17:59:46.151  INFO 33100 --- [           main] com.bruceliu.producer.Producer           : 【发送了一条能够正确被路由的消息】,exchange:[test_dlx_exchange_name],routingKey:[user.add],message:[发送第9条消息.]
2019-11-03 17:59:46.151  INFO 33100 --- [           main] com.bruceliu.producer.Producer           : 【发送了一条能够正确被路由的消息】,exchange:[test_dlx_exchange_name],routingKey:[user.add],message:[发送第10条消息.]
2019-11-03 17:59:46.151  INFO 33100 --- [           main] com.bruceliu.producer.Producer           : 【发送了第一条不能正确被路由的消息】,exchange:[test_dlx_exchange_name],routingKey:[user.delete],message:[不能正确被路由的消息1]
2019-11-03 17:59:46.151  INFO 33100 --- [           main] com.bruceliu.producer.Producer           : 【发送了第一条不能正确被路由的消息】,exchange:[test_dlx_exchange_name],routingKey:[user.delete],message:[不能正确被路由的消息2]
2019-11-03 17:59:46.151  INFO 33100 --- [ 127.0.0.1:5672] c.b.callback.CustomConfirmCallback       : (start)生产者消息确认=========================
2019-11-03 17:59:46.151  INFO 33100 --- [ 127.0.0.1:5672] c.b.callback.CustomConfirmCallback       : (end)生产者消息确认=========================

2019-11-03 17:59:46.151  INFO 33100 --- [ 127.0.0.1:5672] c.b.callback.CustomConfirmCallback       : (start)生产者消息确认=========================
2019-11-03 17:59:46.151  INFO 33100 --- [ 127.0.0.1:5672] c.b.callback.CustomConfirmCallback       : (end)生产者消息确认=========================

2019-11-03 17:59:46.151  INFO 33100 --- [ 127.0.0.1:5672] c.b.callback.CustomConfirmCallback       : (start)生产者消息确认=========================
2019-11-03 17:59:46.151  INFO 33100 --- [ 127.0.0.1:5672] c.b.callback.CustomConfirmCallback       : (end)生产者消息确认=========================
2019-11-03 17:59:46.151  INFO 33100 --- [ 127.0.0.1:5672] c.b.callback.CustomConfirmCallback       : (start)生产者消息确认=========================
2019-11-03 17:59:46.151  INFO 33100 --- [ 127.0.0.1:5672] c.b.callback.CustomConfirmCallback       : (end)生产者消息确认=========================
2019-11-03 17:59:46.167  INFO 33100 --- [ 127.0.0.1:5672] c.b.callback.CustomConfirmCallback       : (start)生产者消息确认=========================
2019-11-03 17:59:46.167  INFO 33100 --- [ 127.0.0.1:5672] c.b.callback.CustomConfirmCallback       : (end)生产者消息确认=========================
2019-11-03 17:59:46.167  INFO 33100 --- [ 127.0.0.1:5672] c.b.callback.CustomConfirmCallback       : (start)生产者消息确认=========================
2019-11-03 17:59:46.167  INFO 33100 --- [ 127.0.0.1:5672] c.b.callback.CustomConfirmCallback       : (end)生产者消息确认=========================
2019-11-03 17:59:46.167  INFO 33100 --- [       Thread-2] o.s.s.concurrent.ThreadPoolTaskExecutor  : Shutting down ExecutorService 'applicationTaskExecutor'

消费者:

2019-11-03 17:59:46.151  INFO 32904 --- [ntContainer#0-1] com.bruceliu.consumer.Consumer           : 【Consumer】接收到消息:[发送第1条消息.]
2019-11-03 17:59:46.151  INFO 32904 --- [ntContainer#0-1] com.bruceliu.consumer.Consumer           : 【Consumer】拒绝一条信息:[发送第1条消息.],该消息将会被转发到死信交换器中
2019-11-03 17:59:46.151  INFO 32904 --- [ntContainer#0-1] com.bruceliu.consumer.Consumer           : 【Consumer】接收到消息:[发送第2条消息.]
2019-11-03 17:59:46.151  INFO 32904 --- [ntContainer#0-1] com.bruceliu.consumer.Consumer           : 【Consumer】拒绝一条信息:[发送第2条消息.],该消息将会被转发到死信交换器中
2019-11-03 17:59:46.151  INFO 32904 --- [ntContainer#0-1] com.bruceliu.consumer.Consumer           : 【Consumer】接收到消息:[发送第3条消息.]
2019-11-03 17:59:46.167  INFO 32904 --- [ntContainer#0-1] com.bruceliu.consumer.Consumer           : 【Consumer】接收到消息:[发送第4条消息.]
2019-11-03 17:59:46.167  INFO 32904 --- [ntContainer#0-1] com.bruceliu.consumer.Consumer           : 【Consumer】拒绝一条信息:[发送第4条消息.],该消息将会被转发到死信交换器中
2019-11-03 17:59:46.167  INFO 32904 --- [ntContainer#0-1] com.bruceliu.consumer.Consumer           : 【Consumer】接收到消息:[发送第5条消息.]
2019-11-03 17:59:46.167  INFO 32904 --- [ntContainer#0-1] com.bruceliu.consumer.Consumer           : 【Consumer】拒绝一条信息:[发送第5条消息.],该消息将会被转发到死信交换器中
2019-11-03 17:59:46.167  INFO 32904 --- [ntContainer#0-1] com.bruceliu.consumer.Consumer           : 【Consumer】接收到消息:[发送第6条消息.]
2019-11-03 17:59:46.167  INFO 32904 --- [ntContainer#0-1] com.bruceliu.consumer.Consumer           : 【Consumer】拒绝一条信息:[发送第6条消息.],该消息将会被转发到死信交换器中
2019-11-03 17:59:46.167  INFO 32904 --- [ntContainer#0-1] com.bruceliu.consumer.Consumer           : 【Consumer】接收到消息:[发送第7条消息.]
2019-11-03 17:59:46.167  INFO 32904 --- [ntContainer#0-1] com.bruceliu.consumer.Consumer           : 【Consumer】拒绝一条信息:[发送第7条消息.],该消息将会被转发到死信交换器中
2019-11-03 17:59:46.167  INFO 32904 --- [ntContainer#0-1] com.bruceliu.consumer.Consumer           : 【Consumer】接收到消息:[发送第8条消息.]
2019-11-03 17:59:46.167  INFO 32904 --- [ntContainer#0-1] com.bruceliu.consumer.Consumer           : 【Consumer】接收到消息:[发送第9条消息.]
2019-11-03 17:59:46.167  INFO 32904 --- [ntContainer#0-1] com.bruceliu.consumer.Consumer           : 【Consumer】接收到消息:[发送第10条消息.]
2019-11-03 17:59:46.167  INFO 32904 --- [ntContainer#0-1] com.bruceliu.consumer.Consumer           : 【Consumer】拒绝一条信息:[发送第10条消息.],该消息将会被转发到死信交换器中

由上图可见,生产者发送了12条消息,其中有两条消息不能被正确路由到队列的,那么这两条消息应该被转发到备份交换机上所绑定的队列上面;其中也有7条消息被拒绝了,那么将会被转发到死信交换机对应的死信队列中,可以观察MQ管理控制台:
RabbitMQ死信队列和备份交换器_第2张图片
RabbitMQ死信队列和备份交换器_第3张图片

arguments.put("x-dead-letter-exchange", DEAD_LETTERS_EXCHANGE_NAME);    //指定死信发送的Exchange
arguments.put("alternate-exchange", MESSAGE_BAK_EXCHANGE_NAME);     //声明备份交换机

3.应用场景

实际工作中,死信队列可以应用在许多场景中,例如常见的过期未支付订单自动取消就可以通过 (死信队列 + 过期时间)来实现,就是当有一个队列 queue1,其 对应的死信交换机 为 deadEx1,deadEx1 绑定了一个队列 deadQueue1,
当队列 queue1 中有一条消息因过期(假设30分钟未支付就取消订单)或者其他原因成为死信的消息,消息就会被转发到死信队列上面,然后我们可以通过监听死信队列中的消息,同时可以加上判断订单的状态是否已经支付,如果已经支付那么不处理,如果未支付,那么可以更新订单状态为已取消。(也就相当于消费的是因过期产生的死信订单信息)。

对比未使用消息队列的时候的解决方案:

设置一个定时器,每秒轮询数据库查找超出过期时间且未支付的订单,然后修改状态,但是这种方式会占用很多资源

相比较而言,使用消息队列可以减少对数据库的压力,在高流量的情况下可以提高系统的响应速度。

4.总结

本文通过一个简单的示例说明了在RabbitMQ中如何使用死信队列和备份交换机,主要点就是声明队列的时候使用x-dead-letter-exchange参数指定死信交换机,声明交换机的时候使用alternate-exchange参数指定备份交换机是哪一个,这样死信消息就会被正确转发到死信交换机绑定的队列上,未被正确路由的消息会被转发到备份交换机对应的备份队列上,根据具体的业务场景,我们可通过监听死信队列或者备份队列进行进一步的处理工作。

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