Add a diagnostic source event that fires when a route is matched

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 @@ public class ComponentEndpointRouteBuilderExtensionsTest
         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 @@ public void MapBlazorHub_WiresUp_UnderlyingHub()
         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 @@ public void MapBlazorHub_MostGeneralOverload_MapsUnderlyingHub()
             // 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 @@ public EndpointRoutingMiddleware(
             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 @@ private Task SetRoutingAndContinue(HttpContext httpContext)
             }
             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 @@ private IServiceProvider CreateServices(MatcherFactory matcherFactory)
             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 @@ public async Task Invoke_OnCall_WritesToConfiguredLogger()
         {
             // 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 @@ public async Task Invoke_OnCall_WritesToConfiguredLogger()
             Assert.Empty(sink.Scopes);
             var write = Assert.Single(sink.Writes);
             Assert.Equal(expectedMessage, write.State?.ToString());
+            Assert.True(eventFired);
         }
 
         [Fact]
@@ -159,19 +172,46 @@ private HttpContext CreateHttpContext()
         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);
+            }
+        }
     }
 }