RabbitMQ 設置消息的優先級

在RabbitMQ中，可以設置消息的優先級，也就相當於在隊列中置頂某條消息，讓某個消息優先得到處理的功能。

既然是設置消息的優先級，那么就是針對生產者，也就是消息發布端。

設置消息的優先級一共有2個步驟：

1、設置隊列的x-max-priority參數；

2、設置消息的Priority參數。

話不多說，上代碼！

發送端：

            var factory = new ConnectionFactory() { HostName = "localhost",UserName="ty2017",Password="123456",VirtualHost="log" };
            using (var connection = factory.CreateConnection()) {
                using (var channel = connection.CreateModel()) {   
                    //聲明一個隊列，設置x-max-priority參數
                    channel.QueueDeclare("q.test", true, false, false, new Dictionary<string, object> { { "x-max-priority", 30 } });
                   
                    for (int i = 0; i < 6; i++) {
                        var body = Encoding.UTF8.GetBytes(string.Format("第{0}個消息",i+1));
                        var properties = channel.CreateBasicProperties();
                        properties.SetPersistent(true);
                        //設置消息的優先級
                        properties.Priority = (byte)((i == 3)?30:i);  
                        //發布消息
                        channel.BasicPublish(exchange: "",
                                             routingKey: "q.test",
                                             basicProperties: properties,
                                             body: body);                       
                    }

                }
            }

將第四個消息的優先級設置為最大，我們打開Consumer端，看看第四個消息是否被優先處理！

Consumer端代碼如下：

            var factory = new ConnectionFactory() { HostName = "localhost", UserName = "ty2017", Password = "123456",VirtualHost="log" };
            using (var connection = factory.CreateConnection()) {
                using (var channel = connection.CreateModel()) {                  
                    channel.QueueDeclare("q.test", true, false, false, new Dictionary<string, object> { { "x-max-priority", 30 } });                   

                    channel.BasicQos(0, 1, false);

                    var consumer = new EventingBasicConsumer(channel);
                    consumer.Received += (model, ea) => {
                        var body = ea.Body;
                        
                        var message = Encoding.UTF8.GetString(body);
                        Console.WriteLine("優先級:{0}  消息內容:{1}",ea.BasicProperties.Priority, message);  
                        channel.BasicAck(ea.DeliveryTag, false);

                    };
                    channel.BasicConsume(queue: "q.test",
                                         noAck: false,
                                         consumer: consumer);                  
                    Console.ReadLine();
                }
            }

運行Consumer端程序，得到如下結果：

根據結果可以看出，優先級越大的消息越是被優先處理！