rabbitMQ死信队列快速编写记录

1.介绍

1.1 什么是死信队列

再rabbitMQ中，有两个重要的组件。exchange（交换机），queue（队列）。交换机用于路由消息，简单来说就是接收客户端传递的消息，转发到queue中。队列做的事情就是存储消息。
但消息并不会一只存储在队列中。当存在一下三种情况，消息就会死掉

• 队列存储不了过多的消息
• 消息本身存在过期时间

当遇到死掉的消息时，我们通常会将这些死信转发到新的交换机中，这个交换机就叫做死信交换机，而配合死信交换机存储信息的队列，叫做死信队列

1.2 死信队列有什么用

死信队列在构建延迟队列时，有巨大作用。比如用户购票订单，30min不支付就过期。在rabbitMQ中可以这样实现

• 1 存储购票信息到exchange-queue中
• 2 设置消息过期时间为30min
• 3 如果超过30min消息未被消费（消息过期，成为死信），存储死信队列，通知服务取消订单

2. 如何编码

2.1 架构分析

先上绑定架构图

整个流程中，出现了三方。在编写代码时，我们可以分三个大类，分别是producer,consumer1,consumer2。其消息传递顺序如下

• producer -> normal_exchange
• normal_queue -> consumer1
• dead_queue-> consumer2

我们可以在编写consumer1的时候，完成exchange和queue的创建与绑定

2.2 maven坐标

        <dependency>
            <groupId>com.rabbitmqgroupId>
            <artifactId>amqp-clientartifactId>
            <version>5.9.0version>
        dependency>

2.3 工具类编写

rabbitMQ整体的编写流程如下

• 创建Connection工厂
• 配置工厂
• 创建链接
• 获取channel
• 通过channel创建exchange, queue, 关系绑定, 监听消息, 发送消息

因此，我们可以先创建工具类，帮我们获取channel，以此减少开发代码量

public class MQUtils {
    public static Channel getChannel() throws Exception {
        // 创建工厂链接
        ConnectionFactory factory = new ConnectionFactory();
        // 设置工厂
        factory.setHost("your_ip");
        factory.setUsername("your_username");
        factory.setPassword("your_password");
        factory.setVirtualHost("/"); // 基本都是/
        Connection connection = factory.newConnection();
        Channel channel = connection.createChannel();
        return channel;
    }
}

2.4 consumer1编写

public class Consumer1 {
    static String EXCHANGE_NAME = "normal_exchange";
    static String QUEUE_NAME = "normal_queue";
    static String DEAD_EXCHANGE_NAME = "dead_exchange";
    static String DEAD_QUEUE_NAME = "dead_queue";

    public static void main(String[] args) throws Exception{
        Channel channel = MQUtils.getChannel();
        // 普通交换机
        channel.exchangeDeclare(EXCHANGE_NAME, BuiltinExchangeType.DIRECT, false, true, null);
        // 普通队列
        // 配置死信交换机参数
        HashMap<String, Object> map = new HashMap<>();
        // 配置normal_queue连接的dead_exchange
        map.put("x-dead-letter-exchange", DEAD_EXCHANGE_NAME);
        // 设置normal_queue的消息过期时间
        map.put("x-message-ttl", 10000);
        // 设置路由到死信交换机的路由key: lisi
        map.put("x-dead-letter-routing-key", "lisi");
        // map.put("x-max-length", 6); // 设置队列最大长度
        channel.queueDeclare(QUEUE_NAME, false, false, true, map);
        // 绑定普通交换机和普通队列
        channel.queueBind(QUEUE_NAME, EXCHANGE_NAME, "zhangsan");
        // 死信交换机
        channel.exchangeDeclare(DEAD_EXCHANGE_NAME, BuiltinExchangeType.DIRECT, false, true, false, null);
        // 死信队列
        channel.queueDeclare(DEAD_QUEUE_NAME, false, false, true, null);
        // 绑定死信交换机和死信队列
        channel.queueBind(DEAD_QUEUE_NAME, DEAD_EXCHANGE_NAME, "lisi");
        // 监听
        channel.basicConsume(QUEUE_NAME, false, (consumerTag, message) -> {
            System.out.println("监听普通队列: " + new String(message.getBody()));
        }, consumerTag -> {});
    }
}

2.5 consumer2编写

public class Consumer2{
    static String DEAD_QUEUE_NAME = "dead_queue";

    public static void main(String[] args) throws Exception{
        Channel channel = MQUtils.getChannel();

        // 监听
        channel.basicConsume(DEAD_QUEUE_NAME, true, (consumerTag, message) -> {
            System.out.println("监听死信队列: " + new String(message.getBody()));
        }, consumerTag -> {});
    }
}

2.6 producer编写

public class Producer {
    static String EXCHANGE_NAME = "normal_exchange";

    public static void main(String[] args) throws Exception{
        Channel channel = MQUtils.getChannel();
        for (int i = 0; i < 10; i++) {
            String msg = i + "";
            channel.basicPublish(EXCHANGE_NAME, "zhangsan",
                    null,
                    msg.getBytes());
        }
    }
}

3.整合springboot

3.1 架构图

3.2 maven坐标

        <dependency>
            <groupId>org.springframework.bootgroupId>
            <artifactId>spring-boot-starter-amqpartifactId>
            <version>2.3.9.RELEASEversion>
        dependency>

3.3 构建配置类，创建exchange，queue，并绑定

package com.xhf.mq.config;

import org.springframework.amqp.core.*;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class TTLConfig {
    /*-----交换机名称-----*/
    private static final String EXCHANGE_NAME = "X";
    private static final String DEAD_EXCHANGE_NAME = "Y";
    /*-----队列名称-----*/
    private static final String QUEUE_NAME1 = "QA";
    private static final String QUEUE_NAME2 = "QB";
    private static final String DEAD_QUEUE_NAME = "QD";

    // 注册交换机
    @Bean("xExchange")
    public DirectExchange xExchange() {
        return ExchangeBuilder.directExchange(EXCHANGE_NAME)
                .autoDelete()
                .build();
//        return new DirectExchange(EXCHANGE_NAME);
    }

    // 注册死信交换机
    @Bean("deadExchange")
    public DirectExchange deadExchange() {
        return ExchangeBuilder.directExchange(DEAD_EXCHANGE_NAME)
                .autoDelete()
                .build();
    }

    // 注册队列QA
    @Bean("queueA")
    public Queue queueA() {
        return QueueBuilder
                .nonDurable(QUEUE_NAME1)
                .withArgument("x-message-ttl", 10000)
                .withArgument("x-dead-letter-exchange", DEAD_EXCHANGE_NAME)
                .withArgument("x-dead-letter-routing-key", "YD")
                .build();
    }

    // 注册队列QB
    @Bean("queueB")
    public Queue queueB() {
        return QueueBuilder
                .nonDurable(QUEUE_NAME2)
                .withArgument("x-message-ttl", 40000)
                .withArgument("x-dead-letter-exchange", DEAD_EXCHANGE_NAME)
                .withArgument("x-dead-letter-routing-key", "YD")
                .build();
    }

    // 注册队列QD
    @Bean("queueD")
    public Queue queueD() {
        return QueueBuilder
                .nonDurable(DEAD_QUEUE_NAME)
                .build();
    }

    // 绑定普通交换机, 队列
    @Bean
    public Binding queueABindingX(@Qualifier("queueA") Queue queueA, @Qualifier("xExchange") Exchange xExchange) {
        return BindingBuilder.bind(queueA).to(xExchange).with("XA").and(null);
    }

    @Bean
    public Binding queueBBindingX(@Qualifier("queueB") Queue queueB, @Qualifier("xExchange") Exchange xExchange) {
        return BindingBuilder.bind(queueB).to(xExchange).with("XB").and(null);
    }

    // 绑定死信交换机, 队列
    @Bean
    public Binding queueDBindingY(@Qualifier("queueD") Queue queueD, @Qualifier("deadExchange") Exchange deadExchange) {
        return BindingBuilder.bind(queueD).to(deadExchange).with("YD").and(null);
    }
}

3.4 编写生产者(controller的一个方法)

   @GetMapping("/sendToQA")
    public void sendToQA() {
    	// 向X交换机发送消息, 消息通过"XA"路由到队列
        rabbitTemplate.convertAndSend("X", "XA", "hello".getBytes());
    }

3.5 编写消费者(一个类, 方法上加上@RabbitListenner，表明需要监听的queue)

@Component
public class Customer {
    @RabbitListener(queues = "QD")
    public void customer(Message message, Channel channel) {
        byte[] body = message.getBody();
        System.out.println(new String(body));
    }
}

4. 常见参数汇总

• x-dead-letter-exchange ：死信交换机名称
• x-message-ttl：消息time to live时间（过期时间）
• x-dead-letter-routing-key：死信交换机路由key
• x-max-length：队列最大长度