Azure Messaging-ServiceBus Messaging消息队列技术系列6-消息回执

上篇博文中我们介绍了Azure Messaging的重复消息机制、At most once 和At least once.

Azure Messaging-ServiceBus Messaging消息队列技术系列5-重复消息：at-least-once at-most-once

本文中我们主要研究并介绍Azure Messaging的消息回执机制：实际应用场景：

同步收发场景下，消息生产者和消费者双向应答模式，例如：张三写封信送到邮局中转站，然后李四从中转站获得信，然后在写一份回执信，放到中转站，然后张三去取，当然张三写信的时候就得写明回信地址。还

有，生成订单编号场景，发送一个生成订单编号的消息，消息消费者接收生成订单编号的消息，并通过消息回执返回。

Azure Messaging的消息回执机制主要通过：基于带会话的Queue/Topic、SessionId、ReplyTo属性来实现

在代码实现中，我们需要：

1. 两个工作线程，一个线程用于消息发送和接收回执消息，一个线程用于消息接收和发送消息回执。

2. 一个会话标识：ReceiptSession　　

3. 两个队列Queue：RequestQueue：发送消息、接收消息，ResponseQueue：发送回执消息，接收回执消息。

直接Show Code：

首先，我们在ServiceBusMQManager增加一个线程安全的创建带回话的QueueClient方法：

private static object syncObj = new object();/// <summary>/// 获取要求会话带Session的QueueClient/// </summary>/// <param name="queueName">队列名称</param>/// <returns>QueueClient</returns>public QueueClient GetSessionQueueClient(string queueName){var namespaceClient = NamespaceManager.Create();if (!namespaceClient.QueueExists(queueName)){lock (syncObj){if (!namespaceClient.QueueExists(queueName)){var queue = new QueueDescription(queueName) { RequiresSession = true };namespaceClient.CreateQueue(queue);}}}return QueueClient.Create(queueName, ReceiveMode.ReceiveAndDelete);}

然后我们定义一些常量：

        private static readonly string ReplyToSessionId = "ReceiptSession";const double ResponseMessageTimeout = 20.0;private static readonly string requestQueueName = "RequestQueue";private static readonly string responseQueueName = "ResponseQueue";

实现发送并接收回执消息的方法：

        /// <summary>/// 发送并接收回执消息/// </summary>/// <param name="bills"></param>public static void SendMessage(){var manager = new ServiceBusUtils();var responseClient = manager.GetSessionQueueClient(responseQueueName);var requestClient = manager.GetSessionQueueClient(requestQueueName);var messsageReceiver = responseClient.AcceptMessageSession(ReplyToSessionId);var order = CreateSalesOrder(1);//发送消息var message = new BrokeredMessage(order);message.Properties.Add("Type", order.GetType().ToString());message.SessionId = ReplyToSessionId;message.MessageId = "OrderMessage001";message.ReplyTo = responseQueueName;requestClient.Send(message);Console.WriteLine("Send message: " + message.MessageId + ", SalesOrder ID: " + order.OrderID);//接收消息回执var receivedMessage = messsageReceiver.Receive(TimeSpan.FromSeconds(ResponseMessageTimeout * 2));var receivedOrder = receivedMessage.GetBody<SalesOrder>();Console.WriteLine("Receive receipt message: " + receivedMessage.MessageId + ", SalesOrder ID: " + receivedOrder.OrderID);messsageReceiver.Close();}

实现接收消息并发送回执方法：

 1         /// <summary>
 2         /// 接收消息并回执
 3         /// </summary>
 4         public static void ReceiveMessage()
 5         {
 6             var manager = new ServiceBusUtils();
 7 
 8             var requestClient = manager.GetSessionQueueClient(requestQueueName);
 9             var session = requestClient.AcceptMessageSession();
10             var requestMessage = session.Receive();
11            
12             if (requestMessage != null)
13             {
14                 var receivedOrder = requestMessage.GetBody<SalesOrder>();
15                 Console.WriteLine("Receive message: " + requestMessage.MessageId + ", SalesOrder ID: " + receivedOrder.OrderID);
16 
17                 var responseMessage = new BrokeredMessage(receivedOrder);
18                 responseMessage.Properties.Add("Type", receivedOrder.GetType().ToString());
19                 responseMessage.ReplyToSessionId = ReplyToSessionId;
20                 responseMessage.MessageId = "ResponseOrderMessage001";
21                 responseMessage.SessionId = requestMessage.SessionId;
22                
23                 //发送回执消息
24                 var responseClient = manager.GetSessionQueueClient(requestMessage.ReplyTo);
25                 responseClient.Send(responseMessage);
26                 Console.WriteLine("Send receipt message: " + responseMessage.MessageId + ", SalesOrder ID: " + receivedOrder.OrderID);               
27             }
28         }

Main方法中，启动两个工作线程：一个线程用于消息发送和接收回执消息，一个线程用于消息接收和发送消息回执。

因为涉及到Azure Messaging中队列的第一次创建，Azure Messaging是不支持多个请求同时创建同一个队列的，因此，我们两个线程间做一个简单的Task.Delay(3000).Wait();

 1         static void Main(string[] args)
 2         {
 3             var sendTask = Task.Factory.StartNew(() => { SendMessage(); });
 4             Task.Delay(3000).Wait();
 5             var receiveTask = Task.Factory.StartNew(() => { ReceiveMessage(); });
 6 
 7             Task.WaitAll(sendTask, receiveTask);
 8 
 9             Console.ReadKey();           
10         }