Log unhandled exceptions thrown from the AppFunc

src/Microsoft.AspNet.Server.Kestrel/Http/Frame.cs

@@ -187,6 +187,7 @@ namespace Microsoft.AspNet.Server.Kestrel.Http
                         }
                         catch (Exception ex)
                         {
+                            Log.ApplicationError(ex);
                             error = ex;
                         }
                         finally

src/Microsoft.AspNet.Server.Kestrel/Infrastructure/IKestrelTrace.cs

@@ -1,3 +1,4 @@
+using System;
 using Microsoft.Extensions.Logging;
 
 namespace Microsoft.AspNet.Server.Kestrel.Infrastructure
@@ -27,5 +28,7 @@ namespace Microsoft.AspNet.Server.Kestrel.Infrastructure
         void ConnectionWrite(long connectionId, int count);
 
         void ConnectionWriteCallback(long connectionId, int status);
+
+        void ApplicationError(Exception ex);
     }
 }

src/Microsoft.AspNet.Server.Kestrel/Infrastructure/KestrelTrace.cs

@@ -82,6 +82,11 @@ namespace Microsoft.AspNet.Server.Kestrel
             // Reserved: Event ID 12
         }
 
+        public virtual void ApplicationError(Exception ex)
+        {
+            _logger.LogError(13, "An unhandled exception was thrown by the application.", ex);
+        }
+
         public virtual void Log(LogLevel logLevel, int eventId, object state, Exception exception, Func<object, Exception, string> formatter)
         {
             _logger.Log(logLevel, eventId, state, exception, formatter);

test/Microsoft.AspNet.Server.KestrelTests/EngineTests.cs

@@ -7,13 +7,13 @@ using System.Net;
 using System.Net.Sockets;
 using System.Text;
 using System.Threading.Tasks;
+using Microsoft.AspNet.Http.Features;
 using Microsoft.AspNet.Server.Kestrel;
 using Microsoft.AspNet.Server.Kestrel.Filter;
-using Microsoft.AspNet.Server.Kestrel.Http;
 using Microsoft.Dnx.Runtime;
 using Microsoft.Dnx.Runtime.Infrastructure;
+using Microsoft.Extensions.Logging;
 using Xunit;
-using Microsoft.AspNet.Http.Features;
 
 namespace Microsoft.AspNet.Server.KestrelTests
 {
@@ -552,6 +552,9 @@ namespace Microsoft.AspNet.Server.KestrelTests
         {
             bool onStartingCalled = false;
 
+            var testLogger = new TestApplicationErrorLogger();
+            testContext.Log = new KestrelTrace(testLogger);
+
             using (var server = new TestServer(frame =>
             {
                 var response = frame.Get<IHttpResponseFeature>();
@@ -595,6 +598,7 @@ namespace Microsoft.AspNet.Server.KestrelTests
                         "");
 
                     Assert.False(onStartingCalled);
+                    Assert.Equal(2, testLogger.ApplicationErrorsLogged);
                 }
             }
         }
@@ -605,6 +609,9 @@ namespace Microsoft.AspNet.Server.KestrelTests
         {
             bool onStartingCalled = false;
 
+            var testLogger = new TestApplicationErrorLogger();
+            testContext.Log = new KestrelTrace(testLogger);
+
             using (var server = new TestServer(async frame =>
             {
                 var response = frame.Get<IHttpResponseFeature>();
@@ -633,6 +640,7 @@ namespace Microsoft.AspNet.Server.KestrelTests
                         "Hello World");
 
                     Assert.True(onStartingCalled);
+                    Assert.Equal(1, testLogger.ApplicationErrorsLogged);
                 }
             }
         }
@@ -643,6 +651,9 @@ namespace Microsoft.AspNet.Server.KestrelTests
         {
             bool onStartingCalled = false;
 
+            var testLogger = new TestApplicationErrorLogger();
+            testContext.Log = new KestrelTrace(testLogger);
+
             using (var server = new TestServer(async frame =>
             {
                 var response = frame.Get<IHttpResponseFeature>();
@@ -671,6 +682,7 @@ namespace Microsoft.AspNet.Server.KestrelTests
                         "Hello");
 
                     Assert.True(onStartingCalled);
+                    Assert.Equal(1, testLogger.ApplicationErrorsLogged);
                 }
             }
         }
@@ -834,5 +846,29 @@ namespace Microsoft.AspNet.Server.KestrelTests
                 }
             }
         }
+
+        private class TestApplicationErrorLogger : ILogger
+        {
+            public int ApplicationErrorsLogged { get; set; }
+
+            public IDisposable BeginScopeImpl(object state)
+            {
+                throw new NotImplementedException();
+            }
+
+            public bool IsEnabled(LogLevel logLevel)
+            {
+                throw new NotImplementedException();
+            }
+
+            public void Log(LogLevel logLevel, int eventId, object state, Exception exception, Func<object, Exception, string> formatter)
+            {
+                // Application errors are logged using 13 as the eventId.
+                if (eventId == 13)
+                {
+                    ApplicationErrorsLogged++;
+                }
+            }
+        }
     }
 }