利用Service bus中的queue中转消息

有需求就有对策就有市场。

由于公司global的policy，导致对公司外发邮件的service必须要绑定到固定的ip地址，所以别的程序需要调用发邮件程序时，问题就来了，如何在azure上跨service进行work role的调用呢？（work role和web role是两个不同的东西，主要区别在work role是每个单独的不依附与web application，web role则不是）

微软的解决方案有几：

1，  目前发送Email的Cloud Service的workrole同时实现接收发送email的请求，可以有多种接收请求的模式：

a)         通过Azure Service Bus Queue实现，需要发送email的应用将发生的信息打包发送到指定的Azure Service Bus Queue，workrole会侦听该queue，有信息到时接收信息，并触发email发送功能

b)        通过TCP或HTTP协议对外提供侦听服务，该协议的侦听端口通过Cloud Service的endpoint对外开放，需要发送email的应用通过这些服务端口向该workrole发送信息，通知workrole发送email

c)　　　（不推荐，需前期部署时就进行分配）watch out net

此次贪图方便，选了方案一：利用queue进行监听，并触发Email发送功能

Azure Service Bus Queue是一个云端的消息队列PAAS服务，可以参考以下的文档来创建和开发Service Bus Queue的功能：

1，  管理和初步Queue代码：https://www.azure.cn/documentation/articles/service-bus-dotnet-how-to-use-queues/

2，  Service Bus开发指南：https://www.azure.cn/documentation/articles/service-bus-create-queues/

3，  样例代码：https://www.azure.cn/documentation/articles/service-bus-samples/

首先在请求的project中web.config配置：

 <appSettings>
    <add key="Microsoft.ServiceBus.ConnectionString" value="Endpoint=sb://xxx.servicebus.chinacloudapi.cn;SharedAccessKeyName=RootManageSharedAccessKey;SharedAccessKey=xxx" />
  </appSettings>

发送请求的代码：

string connectionString = ConfigurationManager.AppSettings["Microsoft.ServiceBus.ConnectionString"];

            var namespaceManager =
                NamespaceManager.CreateFromConnectionString(connectionString);
            if (!namespaceManager.QueueExists("EmailQueue"))
            {
                namespaceManager.CreateQueue("EmailQueue");
            }
            //queue.AddMessageAsync(new CloudQueueMessage(message));
            QueueClient Client =
    QueueClient.CreateFromConnectionString(connectionString, "EmailQueue");

            // Create message, passing a string message for the body.
            BrokeredMessage message = new BrokeredMessage("Email Message");

            // Set some addtional custom app-specific properties.
            message.Properties["sender"] = sender;
            message.Properties["subject"] = mailSubject;
            message.Properties["address"] = mailAddress;
            message.Properties["body"] = mailBody;

            try
            {
                // Send message to the queue.
                Client.Send(message);
            }
            catch (Exception ex)
            {
                throw ex;
            }

接收service的app.config配置：

<appSettings>
    <!-- Service Bus specific app setings for messaging connections -->
    <add key="Microsoft.ServiceBus.ConnectionString" value="Endpoint=sb://xxx.servicebus.chinacloudapi.cn;SharedAccessKeyName=RootManageSharedAccessKey;SharedAccessKey=xxx" />
  </appSettings>

接收的程序代码：

private void RunServiceBus()
        {
            string connectionString =
   CloudConfigurationManager.GetSetting("Microsoft.ServiceBus.ConnectionString");
            Microsoft.ServiceBus.Messaging.QueueClient Client =
              Microsoft.ServiceBus.Messaging.QueueClient.CreateFromConnectionString(connectionString, "EmailQueue");

            // Configure the callback options.
            OnMessageOptions options = new OnMessageOptions();
            options.AutoComplete = false;
            options.AutoRenewTimeout = TimeSpan.FromMinutes(1);

            string sender = string.Empty;
            string mailSubject = string.Empty;
            string mailAddress = string.Empty;
            string mailBody = string.Empty;

            // Callback to handle received messages.
            Client.OnMessage((message) =>
            {
                try
                {
                    // Process message from queue.                  
                    sender = message.Properties["sender"].ToString();
                    mailSubject = message.Properties["subject"].ToString();
                    mailAddress = message.Properties["address"].ToString();
                    mailBody = message.Properties["body"].ToString();
                    SendEmail(sender, mailSubject, mailAddress, mailBody);

                    // Remove message from queue.
                    message.Complete();
                }
                catch (Exception)
                {
                    // Indicates a problem, unlock message in queue.
                    message.Abandon();
                }
            }, options);

        }