C#通过rabbitmq实现定时任务(延时队列)

本文主要讲解如何通过RabbitMQ实现定时任务(延时队列)

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环境准备

需要在MQ中进行安装插件 地址链接
插件介绍地址：https://www.rabbitmq.com/blog/2015/04/16/scheduling-messages-with-rabbitmq/

使用场景

作为一个新的预支付订单被初始化放置，如果该订单在指定时间内未进行支付，则将被认为超时订单进行关闭处理；电商系统中应用较多，用户购买商品产生订单，但未进行支付，订单产生30分钟内未支付将关闭订单（且满足该场景数量庞大），不可能采用人工干预。

代码介绍

生产者

          var factory = new ConnectionFactory()
            {
                Uri = new Uri("MQ地址")
            };
           
            using var connection = factory.CreateConnection();
            using var channel = connection.CreateModel();


            var exchangeName = "delay-exchange";
            var routingkey = "delay.delay";
            var queueName = "delay_queueName";
            //设置Exchange队列类型
            var argMaps = new Dictionary<string, object>()
            {
                {"x-delayed-type", "topic"}
            };
            //设置当前消息为延时队列
            channel.ExchangeDeclare(exchange: exchangeName, type: "x-delayed-message", true, false, argMaps);
            channel.QueueDeclare(queueName, true, false, false, argMaps);
            channel.QueueBind(queueName, exchangeName, routingkey);
            for (int i = 0; i < 3; i++)
            {
                var time = 1000 * 5;
                var message = $@"发送时间为 {DateTime.Now:yyyy-MM-dd HH:mm:ss} 延时时间为:{time}";
                var body = Encoding.UTF8.GetBytes(message);
                var props = channel.CreateBasicProperties();
                //设置消息的过期时间
                props.Headers = new Dictionary<string, object>()
                {
                    {  "x-delay", 5000 }
                };
                channel.BasicPublish(exchange: exchangeName,
                    routingKey: routingkey,
                    basicProperties: props,
                    body: body);
                Console.WriteLine(message);


            }
            Console.ReadLine();

消费者(自动绑定队列写法)

        var factory = new ConnectionFactory()
            {
                Uri = new Uri(MQ地址)
            };
            using var connection = factory.CreateConnection();
            using var channel = connection.CreateModel();
            var queueName = "delay_queueName";
            channel.QueueDeclare(queueName, true, false, false, null);
            var consumer = new EventingBasicConsumer(channel);
            consumer.Received += (model, ea) =>
            {
                var body = ea.Body;
                var message = Encoding.UTF8.GetString(body);
                var routingKey = ea.RoutingKey;
                Console.WriteLine($@"接受到消息的时间为 {DateTime.Now:yyyy-MM-dd HH:mm:ss},routingKey:{routingKey} message:{message} ");
            };
            channel.BasicConsume(queue: queueName,
                autoAck: true,
                consumer: consumer);
            Console.ReadLine();

消费者(手动绑定队列写法)

  var factory = new ConnectionFactory()
            {
                Uri = new Uri(MQ地址)
            };
             using var connection = factory.CreateConnection();
            using var channel = connection.CreateModel();
            var exchangeName = "delay-exchange";
            var routingkey = "delay.delay";
            var queueName = "delay_queueName";
            var autoDelete = true;

            var argMaps = new Dictionary<string, object>()
            {
                {"x-delayed-type", "topic"}
            };
            channel.ExchangeDeclare(exchange: exchangeName, type: "x-delayed-message", true, false, argMaps);
            channel.QueueDeclare(queueName, true, false, false, argMaps);
            channel.QueueBind(queue: queueName, exchange: exchangeName, routingKey: routingkey);
            //channel.QueueDeclare(queueName, true, false, false, null);
            var consumer = new EventingBasicConsumer(channel);
            consumer.Received += (model, ea) =>
            {
                var body = ea.Body;
                var message = Encoding.UTF8.GetString(body);
                var routingKey = ea.RoutingKey;
                Console.WriteLine($@"接受到消息的时间为 {DateTime.Now:yyyy-MM-dd HH:mm:ss},routingKey:{routingKey} message:{message} ");
            };
            channel.BasicConsume(queue: queueName,
                autoAck: true,
                consumer: consumer);
            Console.ReadLine();

最终实现效果(两个消费者)

在上述实现中，其实主要靠以下参数来帮我们实现当前功能

声明Exchange中的 type: "x-delayed-message" 这个表明当前队列为延时消息队列
声明Exchange中arguments中的 {"x-delayed-type", "topic"} 当前表明当前队列为Topic模式
最后 我们在CreateBasicProperties的Header中设置 { "x-delay", 5000 }来达到消息延时的功能(单位为ms)

建议

如果使用当前模式来做定时任务,在要求消息不丢失的前提下，需要运维同学提供稳定的MQ环境

如有哪里讲得不是很明白或是有错误，欢迎指正
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