C#通過rabbitmq實現定時任務(延時佇列)

本文主要講解如何通過RabbitMQ實現定時任務(延時佇列)

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環境準備

需要在MQ中進行安裝外掛 地址連結
外掛介紹地址：https://www.rabbitmq.com/blog/2015/04/16/scheduling-messages-with-rabbitmq/

使用場景

作為一個新的預支付訂單被初始化放置，如果該訂單在指定時間內未進行支付，則將被認為超時訂單進行關閉處理；電商系統中應用較多，使用者購買商品產生訂單，但未進行支付，訂單產生30分鐘內未支付將關閉訂單（且滿足該場景數量龐大），不可能採用人工干預。

程式碼介紹

生產者

          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";
            //設定Exchange佇列型別
            var argMaps = new Dictionary<string, object>()
            {
                {"x-delayed-type", "topic"}
            };
            //設定當前訊息為延時佇列
            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 = $@"傳送時間為 {DateTime.Now:yyyy-MM-dd HH:mm:ss} 延時時間為:{time}";
                var body = Encoding.UTF8.GetBytes(message);
                var props = channel.CreateBasicProperties();
                //設定訊息的過期時間
                props.Headers = new Dictionary<string, object>()
                {
                    {  "x-delay", 5000 }
                };
                channel.BasicPublish(exchange: exchangeName,
                    routingKey: routingkey,
                    basicProperties: props,
                    body: body);
                Console.WriteLine(message);


            }
            Console.ReadLine();

消費者(自動繫結佇列寫法)

        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($@"接受到訊息的時間為 {DateTime.Now:yyyy-MM-dd HH:mm:ss},routingKey:{routingKey} message:{message} ");
            };
            channel.BasicConsume(queue: queueName,
                autoAck: true,
                consumer: consumer);
            Console.ReadLine();

消費者(手動繫結佇列寫法)

  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($@"接受到訊息的時間為 {DateTime.Now:yyyy-MM-dd HH:mm:ss},routingKey:{routingKey} message:{message} ");
            };
            channel.BasicConsume(queue: queueName,
                autoAck: true,
                consumer: consumer);
            Console.ReadLine();

最終實現效果(兩個消費者)

在上述實現中，其實主要靠以下引數來幫我們實現當前功能

宣告Exchange中的 type: "x-delayed-message" 這個表明當前佇列為延時訊息佇列
宣告Exchange中arguments中的 {"x-delayed-type", "topic"} 當前表明當前佇列為Topic模式
最後 我們在CreateBasicProperties的Header中設定 { "x-delay", 5000 }來達到訊息延時的功能(單位為ms)

建議

如果使用當前模式來做定時任務,在要求訊息不丟失的前提下，需要運維同學提供穩定的MQ環境

如有哪裡講得不是很明白或是有錯誤，歡迎指正
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