运用.NetCore实例讲解RabbitMQ死信队列,延时队列

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一、死信队列

描述：Q1队列绑定了x-dead-letter-exchange(死信交换机)为X2，x-dead-letter-routing-key（死信路由key)指向Q2(队列2)

P(生产者)发送消息经X1(交换机1)路由到Q1(队列1)，Q1的消息触发特定情况，自动把消息经X2(交换机2)路由到Q2(队列2)，C(消费者)直接消息Q2的消息。

特定情况有哪些呢：

1.消息被拒(basic.reject or basic.nack)并且没有重新入队(requeue=false)；
2.当前队列中的消息数量已经超过最大长度(创建队列时指定" x-max-length参数设置队列最大消息数量)。
3.消息在队列中过期，即当前消息在队列中的存活时间已经超过了预先设置的TTL(Time To Live)时间；

这里演示情况1：

假如场景：Q1中队列数据不完整，就算从新处理也会报错，那就可以不ack，把这个消息转到死信队列另外处理。

生产者：

public static void SendMessage()
        {
            //死信交换机
            string dlxexChange = "dlx.exchange";
            //死信队列
            string dlxQueueName = "dlx.queue";

            //消息交换机
            string exchange = "direct-exchange";
            //消息队列
            string queueName = "queue_a";

            using (var connection = RabbitMQHelper.GetConnection())
            {
                using (var channel = connection.CreateModel())
                {

                    //创建死信交换机
                    channel.ExchangeDeclare(dlxexChange, type: ExchangeType.Direct, durable: true, autoDelete: false);
                    //创建死信队列
                    channel.QueueDeclare(dlxQueueName, durable: true, exclusive: false, autoDelete: false);
                    //死信队列绑定死信交换机
                    channel.QueueBind(dlxQueueName, dlxexChange, routingKey: dlxQueueName);

                    // 创建消息交换机
                    channel.ExchangeDeclare(exchange, type: ExchangeType.Direct, durable: true, autoDelete: false);
                    //创建消息队列,并指定死信队列
                    channel.QueueDeclare(queueName, durable: true, exclusive: false, autoDelete: false, arguments:
                                        new Dictionary<string, object> {
                                             { "x-dead-letter-exchange",dlxexChange}, //设置当前队列的DLX(死信交换机)
                                             { "x-dead-letter-routing-key",dlxQueueName}, //设置DLX的路由key，DLX会根据该值去找到死信消息存放的队列
                                         });
                    //消息队列绑定消息交换机
                    channel.QueueBind(queueName, exchange, routingKey: queueName);

                    string message = "hello rabbitmq message";
                    var properties = channel.CreateBasicProperties();
                    properties.Persistent = true;
                    //发布消息
                    channel.BasicPublish(exchange: exchange,
                                         routingKey: queueName,
                                         basicProperties: properties,
                                         body: Encoding.UTF8.GetBytes(message));
                    Console.WriteLine($"向队列:{queueName}发送消息:{message}");
                }
            }
        }

消费者：

public static void Consumer()
        {
            //死信交换机
            string dlxexChange = "dlx.exchange";
            //死信队列
            string dlxQueueName = "dlx.queue";

            //消息交换机
            string exchange = "direct-exchange";
            //消息队列
            string queueName = "queue_a";
            var connection = RabbitMQHelper.GetConnection();
            {
                //创建信道
                var channel = connection.CreateModel();
                {

                    //创建死信交换机
                    channel.ExchangeDeclare(dlxexChange, type: ExchangeType.Direct, durable: true, autoDelete: false);
                    //创建死信队列
                    channel.QueueDeclare(dlxQueueName, durable: true, exclusive: false, autoDelete: false);
                    //死信队列绑定死信交换机
                    channel.QueueBind(dlxQueueName, dlxexChange, routingKey: dlxQueueName);

                    // 创建消息交换机
                    channel.ExchangeDeclare(exchange, type: ExchangeType.Direct, durable: true, autoDelete: false);
                    //创建消息队列,并指定死信队列
                    channel.QueueDeclare(queueName, durable: true, exclusive: false, autoDelete: false, arguments:
                                        new Dictionary<string, object> {
                                             { "x-dead-letter-exchange",dlxexChange}, //设置当前队列的DLX
                                             { "x-dead-letter-routing-key",dlxQueueName}, //设置DLX的路由key，DLX会根据该值去找到死信消息存放的队列
                                         });
                    //消息队列绑定消息交换机
                    channel.QueueBind(queueName, exchange, routingKey: queueName);


                    var consumer = new EventingBasicConsumer(channel);
                    channel.BasicQos(prefetchSize: 0, prefetchCount: 1, global: true);
                    consumer.Received += (model, ea) =>
                    {
                        //处理业务
                        var message = Encoding.UTF8.GetString(ea.Body.ToArray());
                        Console.WriteLine($"队列{queueName}消费消息:{message},不做ack确认");
                        //channel.BasicAck(ea.DeliveryTag, false);
                        //不ack(BasicNack),且不把消息放回队列(requeue:false)
                        channel.BasicNack(ea.DeliveryTag, false, requeue: false);
                    };
                    channel.BasicConsume(queueName, autoAck: false, consumer);
                }
            }
        }

消费者加上channel.BasickNack()模拟消息处理不了，不ack确认。

执行结果：

RabbitMQ管理界面：

看到消息队列为queue_a，特性有DLX(死信交换机)，DLK（死信路由）。因为消费端不nack，触发了死信，被转发到了死信队列dlx.queue。

二、延时队列

延时队列其实也是配合死信队列一起用，其实就是上面死信队列的第二中情况。给队列添加消息过时时间（TTL），变成延时队列。

简单的描述就是：P(生产者)发送消息到Q1(延时队列)，Q1的消息有过期时间，比如10s，那10s后消息过期就会触发死信，从而把消息转发到Q2（死信队列）。

解决问题场景：像商城下单，未支付时取消订单场景。下单时写一条记录入Q1,延时30分钟后转到Q2，消费Q2，检查订单，支付则不做操作，没支付则取消订单，恢复库存。

生产者代码：

public static void SendMessage()
        {
            //死信交换机
            string dlxexChange = "dlx.exchange";
            //死信队列
            string dlxQueueName = "dlx.queue";

            //消息交换机
            string exchange = "direct-exchange";
            //消息队列
            string queueName = "delay_queue";

            using (var connection = RabbitMQHelper.GetConnection())
            {
                using (var channel = connection.CreateModel())
                {
                    //创建死信交换机
                    channel.ExchangeDeclare(dlxexChange, type: ExchangeType.Direct, durable: true, autoDelete: false);
                    //创建死信队列
                    channel.QueueDeclare(dlxQueueName, durable: true, exclusive: false, autoDelete: false);
                    //死信队列绑定死信交换机
                    channel.QueueBind(dlxQueueName, dlxexChange, routingKey: dlxQueueName);

                    // 创建消息交换机
                    channel.ExchangeDeclare(exchange, type: ExchangeType.Direct, durable: true, autoDelete: false);
                    //创建消息队列,并指定死信队列，和设置这个队列的消息过期时间为10s
                    channel.QueueDeclare(queueName, durable: true, exclusive: false, autoDelete: false, arguments:
                                        new Dictionary<string, object> {
                                             { "x-dead-letter-exchange",dlxexChange}, //设置当前队列的DLX(死信交换机)
                                             { "x-dead-letter-routing-key",dlxQueueName}, //设置DLX的路由key，DLX会根据该值去找到死信消息存放的队列
                                             { "x-message-ttl",10000} //设置队列的消息过期时间
                                        });
                    //消息队列绑定消息交换机
                    channel.QueueBind(queueName, exchange, routingKey: queueName);

                    string message = "hello rabbitmq message";
                    var properties = channel.CreateBasicProperties();
                    properties.Persistent = true;
                    //发布消息
                    channel.BasicPublish(exchange: exchange,
                                         routingKey: queueName,
                                         basicProperties: properties,
                                         body: Encoding.UTF8.GetBytes(message));
                    Console.WriteLine($"{DateTime.Now},向队列:{queueName}发送消息:{message}");
                }
            }
        }

消费者代码：

public static void Consumer()
        {
            //死信交换机
            string dlxexChange = "dlx.exchange";
            //死信队列
            string dlxQueueName = "dlx.queue";
            var connection = RabbitMQHelper.GetConnection();
            {
                //创建信道
                var channel = connection.CreateModel();
                {
                    //创建死信交换机
                    channel.ExchangeDeclare(dlxexChange, type: ExchangeType.Direct, durable: true, autoDelete: false);
                    //创建死信队列
                    channel.QueueDeclare(dlxQueueName, durable: true, exclusive: false, autoDelete: false);
                    //死信队列绑定死信交换机
                    channel.QueueBind(dlxQueueName, dlxexChange, routingKey: dlxQueueName);

                    var consumer = new EventingBasicConsumer(channel);
                    channel.BasicQos(prefetchSize: 0, prefetchCount: 1, global: true);
                    consumer.Received += (model, ea) =>
                    {
                        //处理业务
                        var message = Encoding.UTF8.GetString(ea.Body.ToArray());
                        Console.WriteLine($"{DateTime.Now}，队列{dlxQueueName}消费消息:{message}");
                        channel.BasicAck(ea.DeliveryTag, false);
                    };
                    channel.BasicConsume(dlxQueueName, autoAck: false, consumer);
                }
            }
        }

执行代码：

向延时队列发送消息，监听死信队列，发送和收到消息时间刚好是设置的10s。

RabbitMQ管理界面：

三、延时消息设置不同过期时间

上面的延时队列能解决消息过期时间都是相同的场景，能不能解决消息的过期时间是不一样的呢？

例如场景：机器人客服，为了更像人为操作，收到消息后要随机3-10秒回复客户。

1）队列不设置TTL（消息过期时间），把过期时间设置在消息上。

生产者代码：

public static void SendMessage()
        {
            //死信交换机
            string dlxexChange = "dlx.exchange";
            //死信队列
            string dlxQueueName = "dlx.queue";

            //消息交换机
            string exchange = "direct-exchange";
            //消息队列
            string queueName = "delay_queue";

            using (var connection = RabbitMQHelper.GetConnection())
            {
                using (var channel = connection.CreateModel())
                {
                    //创建死信交换机
                    channel.ExchangeDeclare(dlxexChange, type: ExchangeType.Direct, durable: true, autoDelete: false);
                    //创建死信队列
                    channel.QueueDeclare(dlxQueueName, durable: true, exclusive: false, autoDelete: false);
                    //死信队列绑定死信交换机
                    channel.QueueBind(dlxQueueName, dlxexChange, routingKey: dlxQueueName);

                    // 创建消息交换机
                    channel.ExchangeDeclare(exchange, type: ExchangeType.Direct, durable: true, autoDelete: false);
                    //创建消息队列,并指定死信队列，和设置这个队列的消息过期时间为10s
                    channel.QueueDeclare(queueName, durable: true, exclusive: false, autoDelete: false, arguments:
                                        new Dictionary<string, object> {
                                             { "x-dead-letter-exchange",dlxexChange}, //设置当前队列的DLX(死信交换机)
                                             { "x-dead-letter-routing-key",dlxQueueName}, //设置DLX的路由key，DLX会根据该值去找到死信消息存放的队列
                                             //{ "x-message-ttl",10000} //设置队列的消息过期时间
                                        });
                    //消息队列绑定消息交换机
                    channel.QueueBind(queueName, exchange, routingKey: queueName);

                    string message = "hello rabbitmq message 10s后处理";
                    var properties = channel.CreateBasicProperties();
                    properties.Persistent = true;
                    properties.Expiration = "10000";//消息的有效期10s

                    //发布消息,延时10s
                    channel.BasicPublish(exchange: exchange,
                                         routingKey: queueName,
                                         basicProperties: properties,
                                         body: Encoding.UTF8.GetBytes(message));
                    Console.WriteLine($"{DateTime.Now},向队列:{queueName}发送消息:{message},延时:10s");



                    string message2 = "hello rabbitmq message 5s后处理";
                    var properties2 = channel.CreateBasicProperties();
                    properties2.Persistent = true;
                    properties2.Expiration = "5000";//消息有效期5s

                    //发布消息,延时5s
                    channel.BasicPublish(exchange: exchange,
                                         routingKey: queueName,
                                         basicProperties: properties2,
                                         body: Encoding.UTF8.GetBytes(message2));
                    Console.WriteLine($"{DateTime.Now},向队列:{queueName}发送消息:{message2},延时:5s");


                }
            }
        }

消费者代码还是上面延时队列的不变，先试下效果。

生产者向队列中发送一条延时10s的消息再发一条延时5秒的消息，但消费者却先拿到延时10s的，再拿到延时5秒的，我想要的结果是先拿到延时5s的再拿到延时10s的，是什么原因呢。

原因是：队列是先进先出的，而RabbitMQ只会对首位第一条消息做检测，第一条没过期，那么后面的消息就会阻塞住等待前面的过期。

解决办法：增加一个消费者对延时队列消费，不ack，把第一条消息放到队列尾部。一直让消息在流动，这样就能检测到了。

2）新增消费者代码：

public static void SendMessage()
        {
            //死信交换机
            string dlxexChange = "dlx.exchange";
            //死信队列
            string dlxQueueName = "dlx.queue";

            //消息交换机
            string exchange = "direct-exchange";
            //消息队列
            string queueName = "delay_queue";

            using (var connection = RabbitMQHelper.GetConnection())
            {
                using (var channel = connection.CreateModel())
                {
                    //创建死信交换机
                    channel.ExchangeDeclare(dlxexChange, type: ExchangeType.Direct, durable: true, autoDelete: false);
                    //创建死信队列
                    channel.QueueDeclare(dlxQueueName, durable: true, exclusive: false, autoDelete: false);
                    //死信队列绑定死信交换机
                    channel.QueueBind(dlxQueueName, dlxexChange, routingKey: dlxQueueName);

                    // 创建消息交换机
                    channel.ExchangeDeclare(exchange, type: ExchangeType.Direct, durable: true, autoDelete: false);
                    //创建消息队列,并指定死信队列，和设置这个队列的消息过期时间为10s
                    channel.QueueDeclare(queueName, durable: true, exclusive: false, autoDelete: false, arguments:
                                        new Dictionary<string, object> {
                                             { "x-dead-letter-exchange",dlxexChange}, //设置当前队列的DLX(死信交换机)
                                             { "x-dead-letter-routing-key",dlxQueueName}, //设置DLX的路由key，DLX会根据该值去找到死信消息存放的队列
                                             //{ "x-message-ttl",10000} //设置队列的消息过期时间
                                        });
                    //消息队列绑定消息交换机
                    channel.QueueBind(queueName, exchange, routingKey: queueName);

                    string message = "hello rabbitmq message 10s后处理";
                    var properties = channel.CreateBasicProperties();
                    properties.Persistent = true;
                    properties.Expiration = "10000";//消息的有效期10s

                    //发布消息,延时10s
                    channel.BasicPublish(exchange: exchange,
                                         routingKey: queueName,
                                         basicProperties: properties,
                                         body: Encoding.UTF8.GetBytes(message));
                    Console.WriteLine($"{DateTime.Now},向队列:{queueName}发送消息:{message},延时:10s");



                    string message2 = "hello rabbitmq message 5s后处理";
                    var properties2 = channel.CreateBasicProperties();
                    properties2.Persistent = true;
                    properties2.Expiration = "5000";//消息有效期5s

                    //发布消息,延时5s
                    channel.BasicPublish(exchange: exchange,
                                         routingKey: queueName,
                                         basicProperties: properties2,
                                         body: Encoding.UTF8.GetBytes(message2));
                    Console.WriteLine($"{DateTime.Now},向队列:{queueName}发送消息:{message2},延时:5s");


                }
            }
        }

执行效果：

这会得到了想要的效果。

RabbitMQ管理界面：

四、延时消息用延时插件的方式实现

相比上面第三的延时消息，这里的插件方式会显的更加简单，也推荐用这种。

因为这里只需要一个交换机和一个对队列，生产者向队列发送消息，会直接是延时才会到队列。

安装插件：

地址：https://www.rabbitmq.com/community-plugins.html

找到和自己RabbitMQ一样的版本，下载下来上传到Linux，或F12查看这个文件的地址，直接Linux上下载(这里用这种)

Linux下载插件：

#下载插件
wget https://github.com/rabbitmq/rabbitmq-delayed-message-exchange/releases/download/3.9.0/rabbitmq_delayed_message_exchange-3.9.0.ez

已经下载到Linux上

#把文件复制到rabbitmq docker容器下的plugins文件夹
docker cp rabbitmq_delayed_message_exchange-3.9.0.ez rabbitmq:/plugins

#进入rabbitmq docker容器
docker exec -it rabbitmq bash

#开启插件：
rabbitmq-plugins enable rabbitmq_delayed_message_exchange

做完上面这些在RabbitMQ管理界面可以看到多了一个延时消息的交换机。

插件装好了，生产者代码：

public static void SendMessage()
        {
            //延时消息交换机
            string delayExchange = "delay.exchange";
            //延时消息队列
            string delayQueueName = "delay_queue";

            using (var connection = RabbitMQHelper.GetConnection())
            {
                using (var channel = connection.CreateModel())
                {
                    Dictionary<string, object> args = new Dictionary<string, object>();
                    args.Add("x-delayed-type", "direct"); //x-delayed-type必须加

                    //创建延时交换机,type类型为x-delayed-message
                    channel.ExchangeDeclare(delayExchange, type: "x-delayed-message", durable: true, autoDelete: false,arguments: args);
                    //创建延时消息队列
                    channel.QueueDeclare(delayQueueName, durable: true, exclusive: false, autoDelete: false);
                    //交换机绑定队列
                    channel.QueueBind(delayQueueName, delayExchange, routingKey: delayQueueName);




                    string message = "hello rabbitmq message 10s后处理";
                    var properties = channel.CreateBasicProperties();
                    properties.Persistent = true;
                    //延时时间从header赋值
                    Dictionary<string, object> headers = new Dictionary<string, object>();
                    headers.Add("x-delay", 10000);

                    properties.Headers = headers;
                   

                    //发布消息,按时10s
                    channel.BasicPublish(exchange: delayExchange,
                                         routingKey: delayQueueName,
                                         basicProperties: properties,
                                         body: Encoding.UTF8.GetBytes(message));
                    Console.WriteLine($"{DateTime.Now},向队列:{delayQueueName}发送消息:{message},延时:10s");

                   

                    string message2 = "hello rabbitmq message 5s后处理";
                    var properties2 = channel.CreateBasicProperties();
                    properties2.Persistent = true;
                    //延时时间从header赋值
                    Dictionary<string, object> headers2 = new Dictionary<string, object>();
                    headers2.Add("x-delay", 5000);
                    properties2.Headers = headers2;

                    //发布消息,延时5s
                    channel.BasicPublish(exchange: delayExchange,
                                         routingKey: delayQueueName,
                                         basicProperties: properties2,
                                         body: Encoding.UTF8.GetBytes(message2));
                    Console.WriteLine($"{DateTime.Now},向队列:{delayQueueName}发送消息:{message2},延时:5s");
                }
            }
        }

消费者代码：

public static void DelayMessageConsumer()
        {
            //延时队列
            string queueName = "delay_queue";
            var connection = RabbitMQHelper.GetConnection();
            {
                //创建信道
                var channel = connection.CreateModel();
                {
                    var consumer = new EventingBasicConsumer(channel);
                    channel.BasicQos(prefetchSize: 0, prefetchCount: 1, global: true);
                    consumer.Received += (model, ea) =>
                    {
                        //处理业务
                        var message = Encoding.UTF8.GetString(ea.Body.ToArray());
                        Console.WriteLine($"{DateTime.Now},接收到消息:{message}");
                        channel.BasicAck(ea.DeliveryTag, false);
                    };
                    channel.BasicConsume(queueName, autoAck: false, consumer);
                }
            }
        }

执行代码：

RabbitMQ管理界面，只有一个队列：

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