RabbitMQ 死信队列DLX

Posted 2022-02-25 lflying

死信队列的简单介绍

利用dlx，当消息在一个队列中变成死信之后，它能被重新publish到另一个exchange，这个exchange就是dlx
消息变成死信的以下几种情况
消息被拒绝，并且requeue= false
消息ttl过期
队列达到最大的长度
dlx也是一个正常的exchange，和一般的exchange没什么区别，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，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。

消费端：

package com.flying.rabbitmq.api.dlx;

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

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

public class Consumer 

    
    public static void main(String[] args) throws Exception 
        
        
        ConnectionFactory connectionFactory = new ConnectionFactory();
        connectionFactory.setHost("192.168.11.76");
        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));
        
        
    

自定义消费端：

package com.flying.rabbitmq.api.dlx;

import java.io.IOException;

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

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));
    

生产端：

package com.flying.rabbitmq.api.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("192.168.11.76");
        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<1; i ++)
            
            AMQP.BasicProperties properties = new AMQP.BasicProperties.Builder()
                    .deliveryMode(2)
                    .contentEncoding("UTF-8")
                    .expiration("10000")
                    .build();
            channel.basicPublish(exchange, routingKey, true, properties, msg.getBytes());