Fix #220 - Check to see if headers are sent first now. Also added in …

…defenses for calling into ASP.NET with logging on exceptions

source/Glimpse.AspNet/AspNetFrameworkProvider.cs

@@ -1,4 +1,6 @@
-using System.Web;
+using System;
+using System.Web;
+using Glimpse.AspNet.Extensions;
 using Glimpse.Core.Extensibility;
 using Glimpse.Core.Framework;
 
@@ -11,6 +13,11 @@ public class AspNetFrameworkProvider : IFrameworkProvider
         /// </summary>
         private HttpContextBase context;
 
+        public AspNetFrameworkProvider(ILogger logger)
+        {
+            Logger = logger;
+        }
+
         public IDataStore HttpRequestStore
         {
             get { return new DictionaryDataStoreAdapter(Context.Items); }
@@ -37,36 +44,83 @@ internal HttpContextBase Context
             set { context = value; }
         }
 
+        private ILogger Logger { get; set; }
+
         public void SetHttpResponseHeader(string name, string value)
         {
-            Context.Response.AppendHeader(name, value);
+            if (!Context.HeadersSent())
+            {
+                try
+                {
+                    Context.Response.AppendHeader(name, value);
+                }
+                catch (Exception exception)
+                {
+                    Logger.Error("Exception setting Http response header '{0}' with value '{1}'.", exception, name, value);
+                }
+            }
         }
 
         public void SetHttpResponseStatusCode(int statusCode)
         {
-            Context.Response.StatusCode = statusCode;
-            Context.Response.StatusDescription = null;
+            try
+            {
+                Context.Response.StatusCode = statusCode;
+                Context.Response.StatusDescription = null;
+            }
+            catch (Exception exception)
+            {
+                Logger.Error("Exception setting Http status code with value '{0}'.", exception, statusCode);
+            }
         }
 
         public void SetCookie(string name, string value)
         {
-            Context.Response.Cookies.Add(new HttpCookie(name, value));
+            try
+            {
+                Context.Response.Cookies.Add(new HttpCookie(name, value));
+            }
+            catch (Exception exception)
+            {
+                Logger.Error("Exception setting cookie '{0}' with value '{1}'.", exception, name, value);
+            }
         }
 
         public void InjectHttpResponseBody(string htmlSnippet)
         {
-            var response = Context.Response;
-            response.Filter = new PreBodyTagFilter(htmlSnippet, response.Filter, response.ContentEncoding);
+            try
+            {
+                var response = Context.Response;
+                response.Filter = new PreBodyTagFilter(htmlSnippet, response.Filter, response.ContentEncoding, Logger);
+            }
+            catch (Exception exception)
+            {
+                Logger.Error("Exception injecting Http response body with Html snippet '{0}'.", exception, htmlSnippet);
+            }
         }
 
         public void WriteHttpResponse(byte[] content)
         {
-            Context.Response.BinaryWrite(content);
+            try
+            {
+                Context.Response.BinaryWrite(content);
+            }
+            catch (Exception exception)
+            {
+                Logger.Error("Exception writing Http response.", exception);
+            }
         }
 
         public void WriteHttpResponse(string content)
         {
-            Context.Response.Write(content);
+            try
+            {
+                Context.Response.Write(content);
+            }
+            catch (Exception exception)
+            {
+                Logger.Error("Exception writing Http response.", exception);
+            }
         }
     }
 }

source/Glimpse.AspNet/AspNetServiceLocator.cs

@@ -1,16 +1,25 @@
 using System.Collections.Generic;
+using Glimpse.Core.Extensibility;
 using Glimpse.Core.Framework;
 
 namespace Glimpse.AspNet
 {
     public class AspNetServiceLocator : IServiceLocator
     {
+        private ILogger logger;
+
+        internal ILogger Logger
+        {
+            get { return logger ?? (logger = new NullLogger()); }
+            set { logger = value; }
+        }
+
         public T GetInstance<T>() where T : class
         {
             var type = typeof(T);
             if (type == typeof(IFrameworkProvider))
             {
-                return new AspNetFrameworkProvider() as T;
+                return new AspNetFrameworkProvider(Logger) as T;
             }
 
             if (type == typeof(ResourceEndpointConfiguration))

source/Glimpse.AspNet/Extensions/HttpContextExtensions.cs

@@ -5,6 +5,8 @@ namespace Glimpse.AspNet.Extensions
 {
     public static class HttpContextExtensions
     {
+        private const string HeadersSentKey = "__GlimpseHttpHeadersSent";
+
         public static string GenerateGlimpseScriptTags(this HttpContextBase context)
         {
             var generateScripts = context.Items["__GlimpseClientScriptsStrategy"] as Func<string>;
@@ -16,5 +18,17 @@ public static string GenerateGlimpseScriptTags(this HttpContextBase context)
 
             return generateScripts();
         }
+
+        internal static void HeadersSent(this HttpContextBase context, bool value)
+        {
+            context.Items[HeadersSentKey] = value;
+        }
+
+        internal static bool HeadersSent(this HttpContextBase context)
+        {
+            var result = context.Items[HeadersSentKey] as bool?;
+
+            return result.HasValue ? result.Value : false;
+        }
     }
 }

source/Glimpse.AspNet/HttpApplicationBase.cs

@@ -13,6 +13,8 @@ public abstract class HttpApplicationBase
 
         public abstract event EventHandler PostReleaseRequestState;
 
+        public abstract event EventHandler PreSendRequestHeaders;
+
         public abstract HttpApplicationStateBase Application { get; set; }
     }
 }

source/Glimpse.AspNet/HttpApplicationWrapper.cs

@@ -36,6 +36,12 @@ public HttpApplicationWrapper(HttpApplication httpApplication)
             remove { HttpApplication.PostReleaseRequestState -= value; }
         }
 
+        public override event EventHandler PreSendRequestHeaders
+        {
+            add { HttpApplication.PreSendRequestHeaders += value; }
+            remove { HttpApplication.PreSendRequestHeaders -= value; }
+        }
+
         public override HttpApplicationStateBase Application
         {
             get

source/Glimpse.AspNet/HttpModule.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Reflection;
 using System.Web;
+using Glimpse.AspNet.Extensions;
 using Glimpse.Core.Extensibility;
 using Glimpse.Core.Framework;
 
@@ -9,7 +10,14 @@ namespace Glimpse.AspNet
     public class HttpModule : IHttpModule  
     {
         private static readonly object LockObj = new object();
-        private readonly Factory factory = new Factory(new AspNetServiceLocator());
+        private static readonly Factory Factory;
+
+        static HttpModule()
+        {
+            var serviceLocator = new AspNetServiceLocator();
+            Factory = new Factory(serviceLocator);
+            serviceLocator.Logger = Factory.InstantiateLogger();
+        }
 
         public void Init(HttpApplication httpApplication)
         {
@@ -25,14 +33,15 @@ internal void Init(HttpApplicationBase httpApplication)
         {
             var runtime = GetRuntime(httpApplication.Application);
 
-            AppDomain.CurrentDomain.SetData(Constants.LoggerKey, factory.InstantiateLogger());
+            AppDomain.CurrentDomain.SetData(Constants.LoggerKey, Factory.InstantiateLogger());
 
             if (runtime.IsInitialized || runtime.Initialize())
             {
                 httpApplication.BeginRequest += (context, e) => BeginRequest(WithTestable(context));
                 httpApplication.PostAcquireRequestState += (context, e) => BeginSessionAccess(WithTestable(context));
                 httpApplication.PostRequestHandlerExecute += (context, e) => EndSessionAccess(WithTestable(context));
                 httpApplication.PostReleaseRequestState += (context, e) => EndRequest(WithTestable(context));
+                httpApplication.PreSendRequestHeaders += (context, e) => SendHeaders(WithTestable(context));
                 AppDomain.CurrentDomain.DomainUnload += UnloadDomain;
             }
         }
@@ -73,7 +82,7 @@ internal IGlimpseRuntime GetRuntime(HttpApplicationStateBase applicationState)
 
                     if (runtime == null)
                     {
-                        runtime = factory.InstantiateRuntime();
+                        runtime = Factory.InstantiateRuntime();
 
                         applicationState.Add(Constants.RuntimeKey, runtime);
                     }
@@ -98,6 +107,11 @@ internal void EndRequest(HttpContextBase httpContext)
             runtime.EndRequest();
         }
 
+        internal void SendHeaders(HttpContextBase httpContext)
+        {
+            httpContext.HeadersSent(true);
+        }
+
         private static HttpContextBase WithTestable(object sender)
         {
             var httpApplication = sender as HttpApplication;

source/Glimpse.AspNet/PreBodyTagFilter.cs

@@ -1,12 +1,13 @@
 using System.IO;
 using System.Text;
 using System.Text.RegularExpressions;
+using Glimpse.Core.Extensibility;
 
 namespace Glimpse.AspNet
 {
     public class PreBodyTagFilter : Stream
     {
-        public PreBodyTagFilter(string htmlSnippet, Stream outputStream, Encoding contentEncoding)
+        public PreBodyTagFilter(string htmlSnippet, Stream outputStream, Encoding contentEncoding, ILogger logger)
         {
 #if NET35
             HtmlSnippet = Glimpse.AspNet.Net35.Backport.Net35Backport.IsNullOrWhiteSpace(htmlSnippet) ? string.Empty : htmlSnippet + "</body>";
@@ -17,6 +18,7 @@ public PreBodyTagFilter(string htmlSnippet, Stream outputStream, Encoding conten
             OutputStream = outputStream;
             ContentEncoding = contentEncoding;
             BodyEnd = new Regex("</body>", RegexOptions.Compiled | RegexOptions.Multiline);
+            Logger = logger;
         }
 
         public override bool CanRead
@@ -45,8 +47,10 @@ public override long Position
             set { OutputStream.Position = value; }
         }
 
+        private ILogger Logger { get; set; }
+
         private string HtmlSnippet { get; set; }
-        
+
         private Stream OutputStream { get; set; }
 
         private Encoding ContentEncoding { get; set; }
@@ -87,6 +91,7 @@ public override void Write(byte[] buffer, int offset, int count)
             }
             else
             {
+                Logger.Warn("Unable to locate '</body>' with content encoding '{0}'. Response may be compressed.", ContentEncoding.EncodingName);
                 OutputStream.Write(buffer, offset, count);
             }
         }

source/Glimpse.Test.AspNet/Tester/AspNetFrameworkProviderTester.cs

@@ -1,6 +1,7 @@
 using System.Collections.Generic;
 using System.Web;
 using Glimpse.AspNet;
+using Glimpse.Core.Extensibility;
 using Moq;
 
 namespace Glimpse.Test.AspNet.Tester
@@ -13,7 +14,7 @@ public class AspNetFrameworkProviderTester : AspNetFrameworkProvider
 
         public Mock<HttpResponseBase> HttpResponseMock { get; set; }
 
-        private AspNetFrameworkProviderTester()
+        private AspNetFrameworkProviderTester(ILogger logger) : base(logger)
         {
             HttpResponseMock = new Mock<HttpResponseBase>();
 
@@ -35,7 +36,7 @@ private AspNetFrameworkProviderTester()
 
         public static AspNetFrameworkProviderTester Create()
         {
-            return new AspNetFrameworkProviderTester();
+            return new AspNetFrameworkProviderTester(new Mock<ILogger>().Object);
         }
     }
 }