Add a diagnostic source event that fires when a route is matched (#11685)

* Add a diagnostic source event that fires when a route is matched
- Usually more information becomes available about a request once route is matched. This event shoud allow diagnositc systems to enlighten the typical "begin request" metadata to include more information about the matched route and more importantly the selected endpoint and associated metadata.

* Update src/Http/Routing/test/UnitTests/EndpointRoutingMiddlewareTest.cs

Co-Authored-By: campersau <buchholz.bastian@googlemail.com>

* PR feedback and test fixes

src/Components/Server/test/ComponentEndpointRouteBuilderExtensionsTest.cs

@@ -1,6 +1,7 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+using System.Diagnostics;
 using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Http;
 using Microsoft.Extensions.DependencyInjection;
@@ -16,12 +17,7 @@ namespace Microsoft.AspNetCore.Components.Server.Tests
         public void MapBlazorHub_WiresUp_UnderlyingHub()
         {
             // Arrange
-            var applicationBuilder = new ApplicationBuilder(
-                new ServiceCollection()
-                .AddLogging()
-                .AddSingleton(Mock.Of<IHostApplicationLifetime>())
-                .AddSignalR().Services
-                .AddServerSideBlazor().Services.BuildServiceProvider());
+            var applicationBuilder = CreateAppBuilder();
             var called = false;
 
             // Act
@@ -40,12 +36,7 @@ namespace Microsoft.AspNetCore.Components.Server.Tests
         public void MapBlazorHub_MostGeneralOverload_MapsUnderlyingHub()
         {
             // Arrange
-            var applicationBuilder = new ApplicationBuilder(
-                new ServiceCollection()
-                .AddLogging()
-                .AddSingleton(Mock.Of<IHostApplicationLifetime>())
-                .AddSignalR().Services
-                .AddServerSideBlazor().Services.BuildServiceProvider());
+            var applicationBuilder = CreateAppBuilder();
             var called = false;
 
             // Act
@@ -59,5 +50,23 @@ namespace Microsoft.AspNetCore.Components.Server.Tests
             // Assert
             Assert.True(called);
         }
+        
+        private IApplicationBuilder CreateAppBuilder()
+        {
+            var services = new ServiceCollection();
+            services.AddSingleton(Mock.Of<IHostApplicationLifetime>());
+            services.AddLogging();
+            services.AddOptions();
+            var listener = new DiagnosticListener("Microsoft.AspNetCore");
+            services.AddSingleton(listener);
+            services.AddSingleton<DiagnosticSource>(listener);
+            services.AddRouting();
+            services.AddSignalR();
+            services.AddServerSideBlazor();
+
+            var serviceProvder = services.BuildServiceProvider();
+
+            return new ApplicationBuilder(serviceProvder);
+        }
     }
 }

src/Http/Routing/src/EndpointRoutingMiddleware.cs

@@ -2,6 +2,7 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
+using System.Diagnostics;
 using System.Runtime.CompilerServices;
 using System.Threading;
 using System.Threading.Tasks;
@@ -13,9 +14,12 @@ namespace Microsoft.AspNetCore.Routing
 {
     internal sealed class EndpointRoutingMiddleware
     {
+        private const string DiagnosticsEndpointMatchedKey = "Microsoft.AspNetCore.Routing.EndpointMatched";
+
         private readonly MatcherFactory _matcherFactory;
         private readonly ILogger _logger;
         private readonly EndpointDataSource _endpointDataSource;
+        private readonly DiagnosticListener _diagnosticListener;
         private readonly RequestDelegate _next;
 
         private Task<Matcher> _initializationTask;
@@ -24,31 +28,18 @@ namespace Microsoft.AspNetCore.Routing
             MatcherFactory matcherFactory,
             ILogger<EndpointRoutingMiddleware> logger,
             IEndpointRouteBuilder endpointRouteBuilder,
+            DiagnosticListener diagnosticListener,
             RequestDelegate next)
         {
-            if (matcherFactory == null)
-            {
-                throw new ArgumentNullException(nameof(matcherFactory));
-            }
-
-            if (logger == null)
-            {
-                throw new ArgumentNullException(nameof(logger));
-            }
-
             if (endpointRouteBuilder == null)
             {
                 throw new ArgumentNullException(nameof(endpointRouteBuilder));
             }
 
-            if (next == null)
-            {
-                throw new ArgumentNullException(nameof(next));
-            }
-
-            _matcherFactory = matcherFactory;
-            _logger = logger;
-            _next = next;
+            _matcherFactory = matcherFactory ?? throw new ArgumentNullException(nameof(matcherFactory));
+            _logger = logger ?? throw new ArgumentNullException(nameof(logger));
+            _diagnosticListener = diagnosticListener ?? throw new ArgumentNullException(nameof(diagnosticListener));
+            _next = next ?? throw new ArgumentNullException(nameof(next));
 
             _endpointDataSource = new CompositeEndpointDataSource(endpointRouteBuilder.DataSources);
         }
@@ -106,6 +97,13 @@ namespace Microsoft.AspNetCore.Routing
             }
             else
             {
+                // Raise an event if the route matched
+                if (_diagnosticListener.IsEnabled() && _diagnosticListener.IsEnabled(DiagnosticsEndpointMatchedKey))
+                {
+                    // We're just going to send the HttpContext since it has all of the relevant information
+                    _diagnosticListener.Write(DiagnosticsEndpointMatchedKey, httpContext);
+                }
+
                 Log.MatchSuccess(_logger, endpoint);
             }
 

src/Http/Routing/test/UnitTests/Builder/EndpointRoutingApplicationBuilderExtensionsTest.cs

@@ -3,6 +3,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Diagnostics;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.Http.Features;
@@ -311,6 +312,9 @@ namespace Microsoft.AspNetCore.Builder
             services.AddLogging();
             services.AddOptions();
             services.AddRouting();
+            var listener = new DiagnosticListener("Microsoft.AspNetCore");
+            services.AddSingleton(listener);
+            services.AddSingleton<DiagnosticSource>(listener);
 
             var serviceProvder = services.BuildServiceProvider();
 

src/Http/Routing/test/UnitTests/EndpointRoutingMiddlewareTest.cs

@@ -2,6 +2,8 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
+using System.Collections.Generic;
+using System.Diagnostics;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Http;
@@ -57,16 +59,26 @@ namespace Microsoft.AspNetCore.Routing
         {
             // Arrange
             var expectedMessage = "Request matched endpoint 'Test endpoint'";
+            bool eventFired = false;
 
             var sink = new TestSink(
                 TestSink.EnableWithTypeName<EndpointRoutingMiddleware>,
                 TestSink.EnableWithTypeName<EndpointRoutingMiddleware>);
             var loggerFactory = new TestLoggerFactory(sink, enabled: true);
+            var listener = new DiagnosticListener("TestListener");
+
+            using var subscription = listener.Subscribe(new DelegateObserver(pair =>
+            {
+                eventFired = true;
+
+                Assert.Equal("Microsoft.AspNetCore.Routing.EndpointMatched", pair.Key);
+                Assert.IsAssignableFrom<HttpContext>(pair.Value);
+            }));
 
             var httpContext = CreateHttpContext();
 
             var logger = new Logger<EndpointRoutingMiddleware>(loggerFactory);
-            var middleware = CreateMiddleware(logger);
+            var middleware = CreateMiddleware(logger, listener: listener);
 
             // Act
             await middleware.Invoke(httpContext);
@@ -75,6 +87,7 @@ namespace Microsoft.AspNetCore.Routing
             Assert.Empty(sink.Scopes);
             var write = Assert.Single(sink.Writes);
             Assert.Equal(expectedMessage, write.State?.ToString());
+            Assert.True(eventFired);
         }
 
         [Fact]
@@ -159,19 +172,46 @@ namespace Microsoft.AspNetCore.Routing
         private EndpointRoutingMiddleware CreateMiddleware(
             Logger<EndpointRoutingMiddleware> logger = null,
             MatcherFactory matcherFactory = null,
+            DiagnosticListener listener = null,
             RequestDelegate next = null)
         {
             next ??= c => Task.CompletedTask;
             logger ??= new Logger<EndpointRoutingMiddleware>(NullLoggerFactory.Instance);
             matcherFactory ??= new TestMatcherFactory(true);
+            listener ??= new DiagnosticListener("Microsoft.AspNetCore");
 
             var middleware = new EndpointRoutingMiddleware(
                 matcherFactory,
                 logger,
                 new DefaultEndpointRouteBuilder(Mock.Of<IApplicationBuilder>()),
+                listener,
                 next);
 
             return middleware;
         }
+
+        private class DelegateObserver : IObserver<KeyValuePair<string, object>>
+        {
+            private readonly Action<KeyValuePair<string, object>> _onNext;
+
+            public DelegateObserver(Action<KeyValuePair<string, object>> onNext)
+            {
+                _onNext = onNext;
+            }
+            public void OnCompleted()
+            {
+
+            }
+
+            public void OnError(Exception error)
+            {
+
+            }
+
+            public void OnNext(KeyValuePair<string, object> value)
+            {
+                _onNext(value);
+            }
+        }
     }
 }