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.NETCore基于RabbitMQ实现延时队列的两方法

2024-04-02 19:55

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前言

此文章用来记录自己学习延时队列过程的文章，并用.NET这两种方式实现了简单的Demo。

延时队列的应用场景应用下单后，30分钟没有支付的话，则自动取消订单活动开始前30分钟，提醒参赛者参加活动。活动结束后，30分钟后提醒未进行评价的参赛人员进行评价…

上述的场景都可以使用延时队列进行对应的处理。

上面的场景虽说可以通过定时器也可以处理，但有点浪费资源，而上述的场景时间是不定的，例如有两个活动需要提醒参赛者参加，一个是7点开始，另一个是8点开始，那么触发处理的一个是6点半，一个是7点半。

实现延时队列的两种方式

使用Rabbitmq实现延时队列可以让消息持久化，也支持分布式

	缺点
第一种	第一种方式的缺陷以及解决方案
第二种	这个插件的当前设计并不真正适合具有大量延迟消息（例如成百上千或数百万）的场景。详情信息

利用rabbitmq死信队列x-dead-letter-exchange和x-dead-letter-routing-key

实现需要创建两对交换机和队列，其中需要对其中一对的队列进行设置x-dead-letter-exchange和x-dead-letter-routing-key属性，属性指定转发到另一对的交换机，

随后实现流程图如下：

.NETCore实现方式

项目：.NET Core 控制台项目

install-package RabbitMQ.Client

生产者代码：

            ConnectionFactory connectionFactory = new ConnectionFactory
            {
                UserName = "guest",
                Password = "guest",
                HostName = "127.0.0.1"
            };

            //创建连接
            var connection = connectionFactory.CreateConnection();

            //创建通道
            var channl = connection.CreateModel();

           //指定队列的x-dead-letter-exchange和x-dead-letter-routing-key
            Dictionary<string, object> queueArgs = new Dictionary<string, object>()
            {
                { "x-dead-letter-exchange","exchange.business.test" },
                {"x-dead-letter-routing-key","businessRoutingkey" }
            };

            //延时的交换机和队列绑定
            channl.ExchangeDeclare("exchange.business.dlx", "direct", true, false, null);
            channl.QueueDeclare("queue.business.dlx", true, false, false, queueArgs);
            channl.QueueBind("queue.business.dlx", "exchange.business.dlx", "");

            //业务的交换机和队列绑定
            channl.ExchangeDeclare("exchange.business.test", "direct", true, false, null);
            channl.QueueDeclare("queue.business.test", true, false, false, null);
            channl.QueueBind("queue.business.test", "exchange.business.test", "businessRoutingkey", null);

            Console.WriteLine("生产者开始发送消息");
            while (true)
            {

                string message = Console.ReadLine();
                var body = Encoding.UTF8.GetBytes(message);
                var properties = channl.CreateBasicProperties();
                properties.Persistent = true;
                properties.Expiration = "5000";
                //发送一条延时5秒的消息
                channl.BasicPublish("exchange.business.dlx", "", properties, body);

            }

消费者

            ConnectionFactory connectionFactory = new ConnectionFactory
            {
                UserName = "guest",
                Password = "guest",
                HostName = "127.0.0.1"
            };

            //创建连接
            var connection = connectionFactory.CreateConnection();

            var channel = connection.CreateModel();

            EventingBasicConsumer consumer = new EventingBasicConsumer(channel);

            //给消费时添加一个委托
            consumer.Received += (obj, ea) =>
            {
                var message = Encoding.UTF8.GetString(ea.Body.ToArray());
                //打印消费的消息
                Console.WriteLine(message);
                channel.BasicAck(ea.DeliveryTag, false);
            };

            //消费queue.business.test队列的消息
            channel.BasicConsume("queue.business.test", false, consumer);

            Console.ReadKey();
            channel.Dispose();
            connection.Close();

实现效果：

rabbitmq通过安装插件的形式实现(推荐)

使用rabbitmq_delayed_message_exchange 插件提供的x-delayed-message类型的交换机

下载插件的地址：https://www.rabbitmq.com/community-plugins.html
选中rabbitmq_delayed_message_exchange插件

该插件使用只需要声明交换机的时候，指定x-delayed-message类型，然后添加x-delayed-type参数即可

.NET Core 实现

生产者

            ConnectionFactory connectionFactory = new ConnectionFactory()
            {
                UserName = "guest",
                Password = "guest",
                HostName = "127.0.0.1"
            };

            var connection = connectionFactory.CreateConnection();

            var channel = connection.CreateModel();

            Dictionary<string, object> exchangeArgs = new Dictionary<string, object>()
            {
                {"x-delayed-type","direct" }
            };

            //指定x-delayed-message 类型的交换机，并且添加x-delayed-type属性
            channel.ExchangeDeclare("plug.delay.exchange", "x-delayed-message", true, false, exchangeArgs);

            channel.QueueDeclare("plug.delay.queue", true, false, false, null);

            channel.QueueBind("plug.delay.queue", "plug.delay.exchange", "plugdelay");

            var properties = channel.CreateBasicProperties();
            Console.WriteLine("生产者开始发送消息");
            Dictionary<string, object> headers = new Dictionary<string, object>()
            {
                {"x-delay","5000" }
            };
            properties.Persistent = true;
            properties.Headers = headers;
            while (true)
            {

                string message = Console.ReadLine();
                var body = Encoding.UTF8.GetBytes(message);
                channel.BasicPublish("plug.delay.exchange", "plugdelay", properties, body);

            }

消费者：

            ConnectionFactory connectionFactory = new ConnectionFactory
            {
                UserName = "guest",
                Password = "guest",
                HostName = "127.0.0.1"
            };

            //创建连接
            var connection = connectionFactory.CreateConnection();

            var channel = connection.CreateModel();

            EventingBasicConsumer consumer = new EventingBasicConsumer(channel);

            consumer.Received += (obj, ea) =>
            {
                var message = Encoding.UTF8.GetString(ea.Body.ToArray());
                Console.WriteLine(message);
                channel.BasicAck(ea.DeliveryTag, false);
            };

            channel.BasicConsume("plug.delay.queue", false, consumer);

            Console.ReadKey();
            channel.Dispose();
            connection.Close();

实现效果：

第一种方式的缺陷以及解决方案

如果存在A、B消息进入了队列中，A在前，B在后，如果B消息的过期时间比A的过期时间要早，消费的时候，并不会先消费B，再消费A，而是B会等A先消费，即使A要晚过期

举例

生产者代码修改成如下：

            ConnectionFactory connectionFactory = new ConnectionFactory
            {
                UserName = "guest",
                Password = "guest",
                HostName = "127.0.0.1"
            };

            //创建连接
            var connection = connectionFactory.CreateConnection();

            //创建通道
            var channl = connection.CreateModel();

            Dictionary<string, object> queueArgs = new Dictionary<string, object>()
            {
                { "x-dead-letter-exchange","exchange.business.test" },
                {"x-dead-letter-routing-key","businessRoutingkey" }
            };

            //延时的交换机和队列绑定
            channl.ExchangeDeclare("exchange.business.dlx", "direct", true, false, null);
            channl.QueueDeclare("queue.business.dlx", true, false, false, queueArgs);
            channl.QueueBind("queue.business.dlx", "exchange.business.dlx", "");

            //业务的交换机和队列绑定
            channl.ExchangeDeclare("exchange.business.test", "direct", true, false, null);
            channl.QueueDeclare("queue.business.test", true, false, false, null);
            channl.QueueBind("queue.business.test", "exchange.business.test", "businessRoutingkey", null);

            string message1 = "Hello Word!1";
            string message2 = "Hello Word!2";
            var body1 = Encoding.UTF8.GetBytes(message1);
            var body2 = Encoding.UTF8.GetBytes(message2);
            var properties = channl.CreateBasicProperties();
            properties.Persistent = true;
            //先发送过期时间5秒的消息
            properties.Expiration = "5000";
            channl.BasicPublish("exchange.business.dlx", "", properties, body2);

            //再发送过期时间3秒的消息
            properties.Expiration = "3000";
            channl.BasicPublish("exchange.business.dlx", "", properties, body1);

结果：