Windows Azure：Host WCF Service in Azure Worker Role

在Worker Role中承载WCF服务，首先需要配置Endpoint，这个例子配置了Internal和External两个Endpoint，Internal Endpoint仅供Cloud Service内部调用（外部无法访问），External Endpoint可供本地（云之外）的应用调用，配置如图所示：

此处使用TCP协议，注意到对于Internal Endpoint，其端口是动态分配的，在运行时才能获取到分配的端口号。

配置好Endpoint以后，则可以发布WCF服务，代码如下：

this.serviceHost = new ServiceHost(typeof(UserService));

ServiceMetadataBehavior metadataBehavior;
metadataBehavior = this.serviceHost.Description.Behaviors.Find<ServiceMetadataBehavior>();
if (metadataBehavior == null)
{
    metadataBehavior = new ServiceMetadataBehavior();
    this.serviceHost.Description.Behaviors.Add(metadataBehavior);
}

NetTcpBinding tcpBinding = new NetTcpBinding(SecurityMode.None);;

Binding mexTcpBinding = MetadataExchangeBindings.CreateMexTcpBinding();

//Get the Internal Endpoint(dynamic port) at runtime
RoleInstanceEndpoint internalEndpoint = RoleEnvironment.CurrentRoleInstance.InstanceEndpoints["Internal"];

this.serviceHost.AddServiceEndpoint(
   typeof(IUserContract),
   tcpBinding,
   String.Format("net.tcp://{0}/Internal", internalEndpoint.IPEndpoint));


this.serviceHost.AddServiceEndpoint(
    typeof(IMetadataExchange),
    mexTcpBinding,
    String.Format("net.tcp://{0}/MEX", internalEndpoint.IPEndpoint));

RoleInstanceEndpoint externalEndpoint = RoleEnvironment.CurrentRoleInstance.InstanceEndpoints["External"];

this.serviceHost.AddServiceEndpoint(
   typeof(IUserContract),
   tcpBinding,
   String.Format("net.tcp://{0}/External", externalEndpoint.IPEndpoint));

this.serviceHost.AddServiceEndpoint(
    typeof(IMetadataExchange),
    mexTcpBinding,
    String.Format("net.tcp://{0}/MEX", externalEndpoint.IPEndpoint));

try
{
    this.serviceHost.Open();
    Trace.WriteLine("WCF service host started successfully.", "Information");
}
catch (TimeoutException timeoutException)
{
    Trace.WriteLine("The service operation timed out. " + timeoutException.Message, "Error");
}
catch (CommunicationException communicationException)
{
    Trace.WriteLine("Could not start WCF service host. " + communicationException.Message, "Error");
}
catch (Exception ex)
{
    Trace.WriteLine(ex.Message, "Error");
}

这段代码是典型的发布WCF服务的代码，通过添加MEX终结点使得可以解析元数据。在WorkerRole的Run方法中执行该段代码，当Worker Role启动时则会启动WCF服务。
WCF服务发布完成以后，我们来尝试通过Cloud Service内部和外部方式来访问这两个Endpoint。

首先，我们在Cloud Service内部的Web Role中来访问Internal Endpoint。

在访问内部Endpoint时，需要获得Worker Role的Instance，通过InstanceEndpoints获取动态分配的端口号。Client端调用服务的代码如下：

IUserContract service = null;

NetTcpBinding tcpBinding = new NetTcpBinding(SecurityMode.None, false);
EndpointAddress address = null;

string endpointType = "Internal";
string serviceRoleName = "WorkerRoleName";
Role serviceRole = RoleEnvironment.Roles[serviceRoleName];
if (serviceRole.Instances.Count > 0)
{
    RoleInstance instance = serviceRole.Instances[0];
    RoleInstanceEndpoint endpoint = instance.InstanceEndpoints[endpointType];
    address = new EndpointAddress(string.Format("net.tcp://{0}/" + endpointType, endpoint.IPEndpoint));
}

if(address != null)
{
    service = ChannelFactory<IUserContract>.CreateChannel(tcpBinding, address);
}

return service;

请注意：在初始化NetTcpBinding时，由于服务端的安全模式为None，所以客户端必须保持一致。

接下来，我们通过本地WcfTestClient.exe来测试External Endpoint。

(WcfTestClient.exe所在目录，C:\Program Files (x86)\Microsoft Visual Studio 11.0\Common7\IDE）

在WcfTextClient加入服务地址：net.tcp://[yourdomain.cloudapp.net]:10100/mex，其中yourdomain需要替换成自己的Cloud Service的名字。

具体地址请登录Portal获取，如图所示：

通过WcfTestClient解析后，我们发现不仅是External Endpoint，Internal Endpoint同样被解析出来了。如配置文件所示：

<?xml version="1.0" encoding="utf-8"?>
<configuration>
    <system.serviceModel>
        <bindings>
            <netTcpBinding>
                <binding name="NetTcpBinding_IUserContract" sendTimeout="00:05:00">
                    <security mode="None" />
                </binding>
            </netTcpBinding>
        </bindings>
        <client>
            <endpoint address="net.tcp://10.146.150.136:20000/Internal" binding="netTcpBinding"
                bindingConfiguration="NetTcpBinding_IUserContract" contract="IUserContract"
                name="NetTcpBinding_IUserContract" />
            <endpoint address="net.tcp://10.146.150.136:10100/External" binding="netTcpBinding"
                bindingConfiguration="NetTcpBinding_IUserContract" contract="IUserContract"
                name="NetTcpBinding_IUserContract1" />
        </client>
    </system.serviceModel>
</configuration>

我们需要将Internal Endpoint的配置删除，因为根据Azure的安全策略，该Endpoint从外部无法访问。

还有一点非常关键的是，我们看到在address URL中，域名被替换成了IP，这是Worker Role所在虚拟机的内部IP，通过这个IP我们是无法成功调用服务的，需要将IP替换成域名，让Azure DNS去自动解析。修改后的配置如下：

 

<?xml version="1.0" encoding="utf-8"?>
<configuration>
    <system.serviceModel>
        <bindings>
            <netTcpBinding>
                <binding name="NetTcpBinding_IUserContract" sendTimeout="00:05:00">
                    <security mode="None" />
                </binding>
            </netTcpBinding>
        </bindings>
        <client>
            <endpoint address="net.tcp://[yourdomain.cloudapp.net]:10100/External" binding="netTcpBinding"
                bindingConfiguration="NetTcpBinding_IUserContract" contract="IUserContract"
                name="NetTcpBinding_IUserContract1" />
        </client>
    </system.serviceModel>
</configuration>

 

同理，我们在Visual Studio通过Add Service Reference来添加WCF服务时也需要做出上述修改。然后，我们就能成功从外部调用Worker Role Input类型的终结点了。