WCF 可擴(kuò)展性

WCF 提供了許多擴(kuò)展點(diǎn)供開(kāi)發(fā)人員自定義運(yùn)行時(shí)行為。 WCF 在 Channel Layer 之上還提供了一個(gè)高級(jí)運(yùn)行時(shí)，主要是針對(duì)應(yīng)用程序開(kāi)發(fā)人員。在 WCF 文檔中，它常被稱(chēng)為服務(wù)模型層（Service Model Layer）。該高級(jí)運(yùn)行時(shí)主要由一個(gè)稱(chēng)作 Dispatcher（在 ServiceHost 的 Context 中）的組件和一個(gè)稱(chēng)作 Proxy（在客戶(hù)端的 Context 中）的組件組成。

（圖片引自 MSDN Magazine?:?Extending WCF with Custom Behaviors）

每個(gè)擴(kuò)展點(diǎn)都使用接口定義來(lái)擴(kuò)展。

StageInterceptor InterfaceDescription

Parameter Inspection	IParameterInspector	Called before and after invocation to inspect and modify parameter values.
Message Formatting	IDispatchMessageFormatter IClientFormatter	Called to perform serialization and deserialization.
Message Inspection	IDispatchMessageInspector IClientMessageInspector	Called before send or after receive to inspect and replace message contents.
Operation Selection	IDispatchOperationSelector IClientOperationSelector	Called to select the operation to invoke for the given message.
Operation Invoker	IOperationInvoker	Called to invoke the operation.

Behavior 是一種特殊類(lèi)型的類(lèi)，它在 ServiceHost/ChannelFactory 初始化過(guò)程中擴(kuò)展運(yùn)行時(shí)行為。WCF 有四種類(lèi)型的行為：服務(wù)行為、終結(jié)點(diǎn)行為、契約行為和操作行為。

ScopeInterfacePotential Impact

?	?	Service	Endpoint	Contract	Operation
Service	IServiceBehavior	?	?	?	?
Endpoint	IEndpointBehavior	?	?	?	?
Contract	IContractBehavior	?	?	?	?
Operation	IOperationBehavior	?	?	?	?

每種行為類(lèi)型也是通過(guò)不同的接口定義來(lái)擴(kuò)展，它們都共用一組相同的方法。一個(gè)例外是，IServiceBehavior 沒(méi)有 ApplyClientBehavior 方法，因?yàn)榉?wù)行為不能用于客戶(hù)端。

MethodDescription

Validate	Called just before the runtime is built—allows you to perform custom validation on the service description.
AddBindingParameters	Called in the first step of building the runtime, before the underlying channel is constructed, allows you to add parameters to influence the underlying channel stack.
ApplyClientBehavior	Allows behavior to inject proxy (client) extensions. Note that this method is not present on IServiceBehavior.
ApplyDispatchBehavior	Allows behavior to inject dispatcher extensions.

WCF擴(kuò)展點(diǎn)

（圖片引自 lovecindywang = lovecherry 博客）

案例：使用WCF擴(kuò)展記錄服務(wù)調(diào)用時(shí)間

服務(wù)定義：

1 [ServiceContract] 2 public interface ICalculatorService 3 { 4 [OperationContract] 5 int Add(int a, int b); 6 }

服務(wù)實(shí)現(xiàn)：

1 public class CalculatorService : ICalculatorService 2 { 3 public int Add(int a, int b) 4 { 5 return a + b; 6 } 7 }

配置文件：

1 <system.serviceModel> 2 <services> 3 <service name="WcfExtensibilityTestServiceConsole.CalculatorService"> 4 <endpoint address="" binding="netTcpBinding" bindingConfiguration="" 5 contract="WcfExtensibilityTestServiceConsole.ICalculatorService" 6 name="myCalculatorServiceEndpoint"/> 7 <endpoint address="mex" binding="mexTcpBinding" contract="IMetadataExchange"/> 8 <host> 9 <baseAddresses> 10 <add baseAddress="net.tcp://localhost:12345/CalculatorService"/> 11 </baseAddresses> 12 </host> 13 </service> 14 </services> 15 <behaviors> 16 <serviceBehaviors> 17 <behavior> 18 <serviceMetadata/> 19 <serviceDebug includeExceptionDetailInFaults="true"/> 20 </behavior> 21 </serviceBehaviors> 22 </behaviors> 23 </system.serviceModel>

問(wèn)題描述

現(xiàn)在需要記錄每次服務(wù)調(diào)用執(zhí)行所需的時(shí)間，比如可以將測(cè)量的方法執(zhí)行時(shí)間傳遞給 PerformanceCounter 用于性能計(jì)數(shù)，或者直接寫(xiě)入到日志中等。

方式一：直接在方法內(nèi)測(cè)量

1 public class CalculatorService : ICalculatorService 2 { 3 public int Add(int a, int b) 4 { 5 Stopwatch watch = Stopwatch.StartNew(); 6 7 int result = a + b; 8 Thread.Sleep(TimeSpan.FromMilliseconds(123)); // waste time here 9 10 Debug.WriteLine(string.Format("Method [{0}] execution cost [{1}] milliseconds.", 11 "Add", watch.ElapsedMilliseconds)); 12 13 return result; 14 } 15 }

這種方法淺顯易懂，但如果服務(wù)所提供的功能過(guò)多，會(huì)導(dǎo)致大量冗余代碼。

方式二：形成測(cè)量類(lèi)簡(jiǎn)化代碼

1 public class Measure : IDisposable 2 { 3 private Stopwatch _watch = null; 4 5 protected Measure(string methodName) 6 { 7 MethodName = methodName; 8 _watch = new Stopwatch(); 9 } 10 11 public string MethodName { get; private set; } 12 13 public void Start() 14 { 15 _watch.Start(); 16 } 17 18 public void Stop() 19 { 20 _watch.Stop(); 21 22 Debug.WriteLine(string.Format("Measure method [{0}] execution cost [{1}] milliseconds.", 23 MethodName, _watch.ElapsedMilliseconds)); 24 } 25 26 public static Measure StartNew(string methodName) 27 { 28 Measure m = new Measure(methodName); 29 m.Start(); 30 return m; 31 } 32 33 public void Dispose() 34 { 35 Stop(); 36 _watch = null; 37 } 38 } View Code 1 public class CalculatorService : ICalculatorService 2 { 3 public int Add(int a, int b) 4 { 5 using (var measure = Measure.StartNew("Add")) 6 { 7 Thread.Sleep(TimeSpan.FromMilliseconds(123)); // waste time here 8 return a + b; 9 } 10 } 11 }

此種方式簡(jiǎn)化了代碼，但仍然需要在各自方法內(nèi)實(shí)現(xiàn)，并需提供方法名作為參數(shù)。

使用?Message Inspection 來(lái)解決問(wèn)題

我們定義類(lèi)?IncomingMessageLoggerInspector 來(lái)實(shí)現(xiàn)?IDispatchMessageInspector 接口。

1 #region IDispatchMessageInspector Members 2 3 public object AfterReceiveRequest( 4 ref Message request, 5 IClientChannel channel, 6 InstanceContext instanceContext) 7 { 8 var context = OperationContext.Current; 9 if (context == null) return null; 10 11 var operationName = ParseOperationName(context.IncomingMessageHeaders.Action); 12 13 return MarkStartOfOperation( 14 context.EndpointDispatcher.ContractName, operationName, 15 context.SessionId); 16 } 17 18 public void BeforeSendReply(ref Message reply, object correlationState) 19 { 20 var context = OperationContext.Current; 21 if (context == null) return; 22 23 var operationName = ParseOperationName(context.IncomingMessageHeaders.Action); 24 25 MarkEndOfOperation( 26 context.EndpointDispatcher.ContractName, operationName, 27 context.SessionId, correlationState); 28 } 29 30 #endregion

通過(guò)服務(wù)的當(dāng)前上下文實(shí)例，我們可以獲取到服務(wù)被調(diào)用的契約名稱(chēng) ContractName，并且可以在 IncomingMessageHeaders 總解析出被調(diào)用的 OperationName。

我們?cè)诜椒?MarkStartOfOperation 中啟動(dòng) Stopwatch 開(kāi)始測(cè)量執(zhí)行時(shí)間，在方法執(zhí)行完畢后服務(wù)模型會(huì)調(diào)用 BeforeSendReply 并將 Stopwatch 實(shí)例引用傳遞至 correlationState，此時(shí)我們可以在方法 MarkEndOfOperation 中解決時(shí)間測(cè)量，并打印日志。

1 #region Private Methods 2 3 private static string ParseOperationName(string action) 4 { 5 if (string.IsNullOrEmpty(action)) return action; 6 7 string actionName = action; 8 9 int index = action.LastIndexOf('/'); 10 if (index >= 0) 11 { 12 actionName = action.Substring(index + 1); 13 } 14 15 return actionName; 16 } 17 18 private static object MarkStartOfOperation( 19 string inspectorType, string operationName, string sessionId) 20 { 21 var message = string.Format(CultureInfo.InvariantCulture, 22 "Operation [{0}] was called at [{1}] on [{2}] in thread [{3}].", 23 operationName, inspectorType, 24 DateTime.Now.ToString(@"yyyy-MM-dd HH:mm:ss.ffffff", CultureInfo.InvariantCulture), 25 Thread.CurrentThread.ManagedThreadId); 26 27 Debug.WriteLine(message); 28 29 return Stopwatch.StartNew(); 30 } 31 32 private static void MarkEndOfOperation( 33 string inspectorType, string operationName, 34 string sessionId, object correlationState) 35 { 36 var watch = (Stopwatch)correlationState; 37 watch.Stop(); 38 39 var message = string.Format(CultureInfo.InvariantCulture, 40 "Operation [{0}] returned after [{1}] milliseconds at [{2}] on [{3}] in thread [{4}].", 41 operationName, watch.ElapsedMilliseconds, inspectorType, 42 DateTime.Now.ToString(@"yyyy-MM-dd HH:mm:ss.ffffff", CultureInfo.InvariantCulture), 43 Thread.CurrentThread.ManagedThreadId); 44 45 Debug.WriteLine(message); 46 } 47 48 #endregion

此時(shí)，我們需要定義 EndpointBehavior 來(lái)講 Inspector 設(shè)置到?DispatchRuntime 中。

1 public class IncomingMessageLoggerEndpointBehavior : IEndpointBehavior 2 { 3 #region IEndpointBehavior Members 4 5 public void AddBindingParameters( 6 ServiceEndpoint endpoint, 7 BindingParameterCollection bindingParameters) 8 { 9 } 10 11 public void ApplyClientBehavior( 12 ServiceEndpoint endpoint, 13 ClientRuntime clientRuntime) 14 { 15 } 16 17 public void ApplyDispatchBehavior( 18 ServiceEndpoint endpoint, 19 EndpointDispatcher endpointDispatcher) 20 { 21 if (endpointDispatcher != null) 22 { 23 endpointDispatcher.DispatchRuntime.MessageInspectors.Add( 24 new IncomingMessageLoggerInspector()); 25 } 26 } 27 28 public void Validate(ServiceEndpoint endpoint) 29 { 30 } 31 32 #endregion 33 }

然后，我們?cè)?ServiceHost 實(shí)例化后，未Open前，將?IncomingMessageLoggerEndpointBehavior 添加至 Endpoint 的 Behaviors 中。

1 class Program 2 { 3 static void Main(string[] args) 4 { 5 ServiceHost host = new ServiceHost(typeof(CalculatorService)); 6 7 foreach (var endpoint in host.Description.Endpoints) 8 { 9 endpoint.Behaviors.Add(new IncomingMessageLoggerEndpointBehavior()); 10 } 11 12 host.Opened += new EventHandler(delegate(object obj, EventArgs e) 13 { 14 Debug.WriteLine(typeof(CalculatorService).Name + " 服務(wù)已經(jīng)啟動(dòng)！"); 15 }); 16 17 host.Open(); 18 19 Console.ReadKey(); 20 } 21 }

使用 WcfTestClient.exe 調(diào)用服務(wù)，執(zhí)行 2 + 3 查看結(jié)果，

在 Debug 輸出中可以看到，

使用配置文件定制

使用配置文件定制擴(kuò)展的優(yōu)點(diǎn)就是可以按需添加和刪除擴(kuò)展，而無(wú)需改動(dòng)代碼。比如當(dāng)發(fā)現(xiàn)系統(tǒng)有性能問(wèn)題時(shí)，添加該擴(kuò)展來(lái)查看具體哪個(gè)方法執(zhí)行速度慢。

需要定義類(lèi)來(lái)實(shí)現(xiàn)?BehaviorExtensionElement 抽象類(lèi)。

1 public class IncomingMessageLoggerEndpointBehaviorExtension : BehaviorExtensionElement 2 { 3 public override Type BehaviorType 4 { 5 get { return typeof(IncomingMessageLoggerEndpointBehavior); } 6 } 7 8 protected override object CreateBehavior() 9 { 10 return new IncomingMessageLoggerEndpointBehavior(); 11 } 12 }

在配置文件中添加擴(kuò)展項(xiàng)，

1 <extensions> 2 <behaviorExtensions> 3 <add name="incomingMessageLogger" 4 type="WcfExtensibilityTestServiceConsole.Extensions.IncomingMessageLoggerEndpointBehaviorExtension, WcfExtensibilityTestServiceConsole"/> 5 </behaviorExtensions> 6 </extensions>

在終結(jié)點(diǎn)行為中添加該擴(kuò)展定義，

1 <behaviors> 2 <serviceBehaviors> 3 <behavior> 4 <serviceMetadata/> 5 <serviceDebug includeExceptionDetailInFaults="true"/> 6 </behavior> 7 </serviceBehaviors> 8 <endpointBehaviors> 9 <behavior> 10 <incomingMessageLogger/> 11 </behavior> 12 </endpointBehaviors> 13 </behaviors>

使用 ServiceBehavior 擴(kuò)展

同理，如果服務(wù)實(shí)現(xiàn)了多個(gè) Endpoint，則想在所有 Endpoint 上添加該擴(kuò)展，除了可以逐個(gè)添加或者使用?behaviorConfiguration 來(lái)配置。

另一個(gè)方法是可以借助 IServiceBehavior 的擴(kuò)展實(shí)現(xiàn)。

1 public class IncomingMessageLoggerServiceBehavior : IServiceBehavior 2 { 3 #region IServiceBehavior Members 4 5 public void AddBindingParameters( 6 ServiceDescription serviceDescription, 7 ServiceHostBase serviceHostBase, 8 Collection<ServiceEndpoint> endpoints, 9 BindingParameterCollection bindingParameters) 10 { 11 } 12 13 public void ApplyDispatchBehavior( 14 ServiceDescription serviceDescription, 15 ServiceHostBase serviceHostBase) 16 { 17 if (serviceHostBase != null) 18 { 19 foreach (ChannelDispatcher channelDispatcher in serviceHostBase.ChannelDispatchers) 20 { 21 foreach (EndpointDispatcher endpointDispatcher in channelDispatcher.Endpoints) 22 { 23 endpointDispatcher.DispatchRuntime.MessageInspectors.Add( 24 new IncomingMessageLoggerInspector()); 25 } 26 } 27 } 28 } 29 30 public void Validate( 31 ServiceDescription serviceDescription, 32 ServiceHostBase serviceHostBase) 33 { 34 } 35 36 #endregion 37 }

原理相同，僅是遍歷通道分配器中所有的終結(jié)點(diǎn)，逐一添加 Inspector。

同理，如果需要在配置文件中使用，也需要實(shí)現(xiàn)一個(gè)?BehaviorExtensionElement 類(lèi)。

1 public class IncomingMessageLoggerServiceBehaviorExtension : BehaviorExtensionElement 2 { 3 public override Type BehaviorType 4 { 5 get { return typeof(IncomingMessageLoggerServiceBehavior); } 6 } 7 8 protected override object CreateBehavior() 9 { 10 return new IncomingMessageLoggerServiceBehavior(); 11 } 12 }

此時(shí)的配置文件描述如下：

1 <behaviors> 2 <serviceBehaviors> 3 <behavior> 4 <serviceMetadata/> 5 <serviceDebug includeExceptionDetailInFaults="true"/> 6 <incomingMessageLogger/> 7 </behavior> 8 </serviceBehaviors> 9 </behaviors> 10 <extensions> 11 <behaviorExtensions> 12 <add name="incomingMessageLogger" 13 type="WcfExtensibilityTestServiceConsole.Extensions.IncomingMessageLoggerServiceBehaviorExtension, WcfExtensibilityTestServiceConsole"/> 14 </behaviorExtensions> 15 </extensions>

參考資料

• Extending WCF with Custom Behaviors
• WCF Extensibility – Message Inspectors
• WCF擴(kuò)展
• Introduction to Extensibility
• Carlos Figueira MSDN blog

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