实现的原理比较直接，定义一个MessageHandler记录WebAPI的请求记录，然后将这些请求日志推送到客户端，客户端就是一个查看日志的页面，实时将请求日志展示在页面中。

这个例子的目的是演示如何在PersistentConnection类外部给Clients推送消息

实现过程

一、服务端

服务端同时具备SignalR和WebAPI的功能，通过定义一个记录日志的MessageHandler实现对WebAPI请求的拦截，并生成请求记录，然后推送到客户端

step 1

创建一个具备WebAPI功能的站点，为了简化起见，设置Authentication为No Authentication

step 2

创建一个DelegatingHandler，用于记录WebAPI日志，代码如下

下面代码没有涉及到SignalR的功能，日志展示是通过ILoggingDisplay接口传入

public class LoggingHandler : DelegatingHandler     {         private static readonly string _loggingInfoKey = "loggingInfo";        private ILoggingDisplay _loggingDisplay;        public LoggingHandler(ILoggingDisplay loggingDisplay)         {             _loggingDisplay = loggingDisplay;         }        public LoggingHandler(HttpMessageHandler innerHandler, ILoggingDisplay loggingDisplay)             : base(innerHandler)         {             _loggingDisplay = loggingDisplay;         }        protected override Task
     
       SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)         {             LogRequestLoggingInfo(request);             return base.SendAsync(request, cancellationToken).ContinueWith(task =>             {                 var response = task.Result;                 LogResponseLoggingInfo(response);                 return response;             });         }        private void LogRequestLoggingInfo(HttpRequestMessage request)         {             var info = new ApiLoggingInfo();             info.HttpMethod = request.Method.Method;             info.UriAccessed = request.RequestUri.AbsoluteUri;             info.IpAddress = HttpContext.Current != null ? HttpContext.Current.Request.UserHostAddress : "0.0.0.0";             info.StartTime = DateTime.Now;             ExtractMessageHeadersIntoLoggingInfo(info, request.Headers.ToList());             request.Properties.Add(_loggingInfoKey, info);         }        private void LogResponseLoggingInfo(HttpResponseMessage response)         {             object loggingInfoObject = null;             if (!response.RequestMessage.Properties.TryGetValue(_loggingInfoKey, out loggingInfoObject))             {                 return;             }             var info = loggingInfoObject as ApiLoggingInfo;             if (info == null)             {                 return;             }             info.HttpMethod = response.RequestMessage.Method.ToString();             info.ResponseStatusCode = response.StatusCode;             info.ResponseStatusMessage = response.ReasonPhrase;             info.UriAccessed = response.RequestMessage.RequestUri.AbsoluteUri;             info.IpAddress = HttpContext.Current != null ? HttpContext.Current.Request.UserHostAddress : "0.0.0.0";             info.EndTime = DateTime.Now;             info.TotalTime = (info.EndTime - info.StartTime).TotalMilliseconds;             _loggingDisplay.Display(info);         }        private void ExtractMessageHeadersIntoLoggingInfo(ApiLoggingInfo info, List
      
       
        >> headers)         {             headers.ForEach(h =>             {                 var headerValues = new StringBuilder();                if (h.Value != null)                 {                     foreach (var hv in h.Value)                     {                         if (headerValues.Length > 0)                         {                             headerValues.Append(", ");                         }                         headerValues.Append(hv);                     }                 }                 info.Headers.Add(string.Format("{0}: {1}", h.Key, headerValues.ToString()));             });         }     }LoggingHandler
       
      
     

step 3

引入SignalR相关packages

Install-Package Microsoft.AspNet.SignalR

新建一个PersistentConnection，代码为空即可（因为不涉及到客户端调用，推送也是在类的外部执行）

public class RequestMonitor : PersistentConnection

{

}

添加一个Startup类

public void Configuration(IAppBuilder app)

{

       app.MapSignalR<RequestMonitor>("/monitor");

}

step 4

创建一个类实现ILoggingDisplay接口，用SignalR推送的方式实现这个接口

代码比较关键的部分就是通过GlobalHost.ConnectionManager获取当前应用程序的connectionContext,得到这个context就可以类似在PersistentConnection内部给clients推送消息

public class SignalRLoggingDisplay : ILoggingDisplay     {         /// 
         /// PersistentConnection上下文         /// 
         private static IPersistentConnectionContext connectionContext = GlobalHost.ConnectionManager.GetConnectionContext
     
      ();        public void Display(ApiLoggingInfo loggingInfo)         {             var message = new StringBuilder();              message.AppendFormat("StartTime:{0},Method:{1},Url:{2},ReponseStatus:{3},TotalTime:{4}"                 , loggingInfo.StartTime, loggingInfo.HttpMethod, loggingInfo.UriAccessed, loggingInfo.ResponseStatusCode, loggingInfo.TotalTime);             message.AppendLine();             message.AppendFormat("Headers:{0},Body:{1}", string.Join(",", loggingInfo.Headers), loggingInfo.BodyContent);             connectionContext.Connection.Broadcast(message.ToString());         }SignalRLoggingDisplay
     

step 5

在WebApiConfig的Register方法中添加自定义的handler

public static void Register(HttpConfiguration config)        {            config.MapHttpAttributeRoutes();           config.Routes.MapHttpRoute(                name: "DefaultApi",                routeTemplate: "api/{controller}/{id}",                defaults: new { id = RouteParameter.Optional }            );           config.MessageHandlers.Add(new LoggingHandler(new SignalRLoggingDisplay()));        }RegisterHandler

到此完成服务端的功能实现

 

二、客户端

客户端只需要一个监控页面，html页面足矣，其主要功能是提供开始监控、停止监控功能，其他都是接收服务端的推送并展示功能代码。

            
            
Web API Request Logs
     
     
         
               
               
           
     
     
     
                 Monitor

示例