RabbitMQ消息模式（TTL消息、死信队列）

什么是TTL消息

TTL是Time To Live的缩写，也就是生存时间

RabbitMQ支持消息的过期时间，在消息发送时可以进行指定

RabbitMQ支持队列的过期时间，从消息入队列开始计算，只要超过了队列的超时时间配置，那么消息自动的清除；针对队列，只要是这个队列的消息，就只有这么长的存活时间

注意：主要针对消息设置，跟交换机、队列、消费者设置毫无关系

消费端代码：

package com.ue.ttl;

import com.rabbitmq.client.Channel;
import com.rabbitmq.client.Connection;
import com.rabbitmq.client.ConnectionFactory;
import com.rabbitmq.client.QueueingConsumer;

import java.util.Map;

public class Consumer {
    public static void main(String[] args) throws Exception {

        //1、创建一个ConnectionFactory, 并进行配置
        ConnectionFactory connectionFactory = new ConnectionFactory();
        connectionFactory.setHost("192.168.14.758");
        connectionFactory.setPort(5672);
        connectionFactory.setVirtualHost("/");

        //2、通过连接工厂创建连接
        Connection connection = connectionFactory.newConnection();

        //3、通过connection创建一个Channel
        Channel channel = connection.createChannel();

        //4、声明（创建）一个队列
        String queueName = "test001";
        channel.queueDeclare(queueName, true, false, false, null);

        //5、创建消费者
        QueueingConsumer queueingConsumer = new QueueingConsumer(channel);

        //6、设置Channel
        channel.basicConsume(queueName, true, queueingConsumer);

        while(true){
            //7、获取消息
            QueueingConsumer.Delivery delivery = queueingConsumer.nextDelivery();
            String msg = new String(delivery.getBody());
            System.err.println("消费端: " + msg);
            Map<String, Object> headers = delivery.getProperties().getHeaders();
            System.err.println("headers get my1 value: " + headers.get("my1"));
        }
    }
}

生产端代码：

package com.ue.ttl;

import com.rabbitmq.client.AMQP;
import com.rabbitmq.client.Channel;
import com.rabbitmq.client.Connection;
import com.rabbitmq.client.ConnectionFactory;

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

public class Procuder {
    public static void main(String[] args) throws Exception {
        //1、创建一个ConnectionFactory, 并进行配置
        ConnectionFactory connectionFactory = new ConnectionFactory();
        connectionFactory.setHost("192.168.14.758");
        connectionFactory.setPort(5672);
        connectionFactory.setVirtualHost("/");

        //2、通过连接工厂创建连接
        Connection connection = connectionFactory.newConnection();

        //3、通过connection创建一个Channel
        Channel channel = connection.createChannel();

        Map<String, Object> headers = new HashMap<>();
        headers.put("my1", "111");
        headers.put("my2", "222");

        AMQP.BasicProperties properties = new AMQP.BasicProperties.Builder()
                .deliveryMode(2)
                .contentEncoding("UTF-8")
                .expiration("10000")
                .headers(headers)
                .build();

        //4、通过Channel发送数据
        for(int i=0; i < 5; i++){
            String msg = "Hello RabbitMQ!";
            channel.basicPublish("", "test001", properties, msg.getBytes());
        }

        //5、记得要关闭相关的连接
        channel.close();
        connection.close();
    }
}

死信队列

死信队列：DLX，Dead-Letter-Exchange；利用DLX，当消息在一个队列中变成死信（dead message）之后，它能被重新publish到另一个Exchange，这个Exchange就是DLX

消息变成死信有以下几种情况

• 消息被拒绝（basic.reject/basic.nack）并且requeue=false
• 消息TTL过期
• 队列达到最大长度

死信队列的特点

• DLX也是一个正常的Exchange，和一般的Exchange没有区别，它能在任何的队列上被指定，实际上就是设置某个队列的属性
• 当这个队列中有死信时，RabbitMQ就会自动的将这个消息重新发布到设置的Exchange上去，进而被路由到另一个队列
• 可以监听这个队列中消息做相应的处理，这个特性可以弥补RabbitMQ3.0以前支持的immediate参数的功能

死信队列设置

• 首先需要设置死信队列的Exchange和Queue，然后进行绑定：

Exchange：dlx.exchange
Queue：dlx.queue
RoutingKey：#

• 然后我们进行正常声明交换机、队列、绑定，只不过我们需要在队列加上一个参数即可：

Arguments.put(“x-dead-letter-exchange”,”dlx.exchange”);

• 这样消息在过期、requeue、队列在达到最大长度时，消息就可以直接路由到死信队列

自定义消费端代码：

package com.ue.dlx;

import com.rabbitmq.client.AMQP;
import com.rabbitmq.client.Channel;
import com.rabbitmq.client.DefaultConsumer;
import com.rabbitmq.client.Envelope;

import java.io.IOException;

public class MyConsumer extends DefaultConsumer {

    public MyConsumer(Channel channel) {
        super(channel);
    }

    @Override
    public void handleDelivery(String consumerTag, Envelope envelope, AMQP.BasicProperties properties, byte[] body) throws IOException {
        System.err.println("-----------consume message----------");
        System.err.println("consumerTag: " + consumerTag);
        System.err.println("envelope: " + envelope);
        System.err.println("properties: " + properties);
        System.err.println("body: " + new String(body));
    }
}

消费端代码：

package com.ue.dlx;

import com.rabbitmq.client.Channel;
import com.rabbitmq.client.Connection;
import com.rabbitmq.client.ConnectionFactory;

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

public class Consumer {
    public static void main(String[] args) throws Exception {
        ConnectionFactory connectionFactory = new ConnectionFactory();
        connectionFactory.setHost("192.168.14.758");
        connectionFactory.setPort(5672);
        connectionFactory.setVirtualHost("/");

        Connection connection = connectionFactory.newConnection();
        Channel channel = connection.createChannel();

        //这就是一个普通的交换机和队列以及路由
        String exchangeName = "test_dlx_exchange";
        String routingKey = "dlx.#";
        String queueName = "test_dlx_queue";

        channel.exchangeDeclare(exchangeName, "topic", true, false, null);

        Map<String, Object> agruments = new HashMap<String, Object>();
        agruments.put("x-dead-letter-exchange", "dlx.exchange");
        //这个agruments属性，要设置到声明队列上
        channel.queueDeclare(queueName, true, false, false, agruments);
        channel.queueBind(queueName, exchangeName, routingKey);

        //要进行死信队列的声明:
        channel.exchangeDeclare("dlx.exchange", "topic", true, false, null);
        channel.queueDeclare("dlx.queue", true, false, false, null);
        channel.queueBind("dlx.queue", "dlx.exchange", "#");

        channel.basicConsume(queueName, true, new MyConsumer(channel));
    }
}

生产端代码：

package com.ue.dlx;

import com.rabbitmq.client.AMQP;
import com.rabbitmq.client.Channel;
import com.rabbitmq.client.Connection;
import com.rabbitmq.client.ConnectionFactory;

public class Producer {
    public static void main(String[] args) throws Exception {
        ConnectionFactory connectionFactory = new ConnectionFactory();
        connectionFactory.setHost("192.168.14.758");
        connectionFactory.setPort(5672);
        connectionFactory.setVirtualHost("/");

        Connection connection = connectionFactory.newConnection();
        Channel channel = connection.createChannel();

        String exchange = "test_dlx_exchange";
        String routingKey = "dlx.save";

        String msg = "Hello RabbitMQ DLX Message";

        for(int i = 0; i< 3; i ++){

            AMQP.BasicProperties properties = new AMQP.BasicProperties.Builder()
                    .deliveryMode(2)
                    .contentEncoding("UTF-8")
                    .expiration("10000")
                    .build();
            channel.basicPublish(exchange, routingKey, true, properties, msg.getBytes());
        }
    }
}