用SignalR实现实时查看WebAPI请求日志

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<HttpResponseMessage> 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<KeyValuePair<string, IEnumerable<string>>> 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())); 
            }); 
        } 
    }

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 
    { 
        /// <summary> 
        /// PersistentConnection上下文 
        /// </summary> 
        private static IPersistentConnectionContext connectionContext = GlobalHost.ConnectionManager.GetConnectionContext<RequestMonitor>();

        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()); 
        }

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())); 
       }

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。

<!DOCTYPE html> 
<html> 
<head> 
    <title>Web API页面实时请求监控</title> 
    <meta charset="utf-8" /> 
</head> 
<body> 
    <h1>Web API Request Logs</h1> 
    <div> 
        <input type="button" value="start" id="btnStart"/> 
        <input type="button" value="stop" id="btnStop"/> 
        <input type="button" value="clear" id="btnClear"/> 
    </div> 
    <ul id="requests"></ul> 
    <script src="/Scripts/jquery-1.10.2.min.js"></script> 
    <script src="/Scripts/jquery.signalR-2.2.0.min.js"></script> 
    <script> 
        $(function () { 
            var requests = $("#requests"); 
            var startButton = $("#btnStart"); 
            var stopButton = $("#btnStop"); 
            var connection = null;

            enable(stopButton, false); 
            enable(startButton, true);

            startButton.click(function () { 
                startConnection(); 
                enable(stopButton, true); 
                enable(startButton, false); 
            });

            $("#btnClear").click(function () { 
                $("#requests").children().remove(); 
            });

            stopButton.click(function () { 
                stopConnection(); 
                enable(stopButton, false); 
                enable(startButton, true); 
            });

            function startConnection() { 
                stopConnection(); 
                connection = $.connection("/monitor"); 
                connection.start() 
                    .fail(function () { 
                        console.log("connect failed"); 
                    }); 
                connection.received(function (data) { 
                    data = data.replace(/
/g, "<br/>") 
                    data = data.replace(/
/g, "<br/>"); 
                    requests.append("<li>" + data + "</li>"); 
                }); 
            }

            function stopConnection() { 
                if (connection != null){ 
                    connection.stop(); 
                } 
            }

            function enable(button, enabled) { 
                if (enabled) { 
                    button.removeAttr("disabled"); 
                } 
                else { 
                    button.attr("disabled", "disabled"); 
                } 
            } 
        }); 
    </script> 
</body> 
</html>

示例代码下载