Fix #6102 - Intense CPU utilization on page change (#6542)

src/Http/Routing/src/DataSourceDependentCache.cs

@@ -1,4 +1,4 @@
-// Copyright (c) .NET Foundation. All rights reserved.
+// 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;
@@ -8,7 +8,7 @@
 
 namespace Microsoft.AspNetCore.Routing
 {
-    internal class DataSourceDependentCache<T> where T : class
+    internal sealed class DataSourceDependentCache<T> : IDisposable where T : class
     {
         private readonly EndpointDataSource _dataSource;
         private readonly Func<IReadOnlyList<Endpoint>, T> _initializeCore;
@@ -19,13 +19,21 @@ internal class DataSourceDependentCache<T> where T : class
         private bool _initialized;
         private T _value;
 
+        private IDisposable _disposable;
+        private bool _disposed;
+
         public DataSourceDependentCache(EndpointDataSource dataSource, Func<IReadOnlyList<Endpoint>, T> initialize)
         {
             if (dataSource == null)
             {
                 throw new ArgumentNullException(nameof(dataSource));
             }
 
+            if (initialize == null)
+            {
+                throw new ArgumentNullException(nameof(initialize));
+            }
+
             _dataSource = dataSource;
             _initializeCore = initialize;
 
@@ -51,9 +59,32 @@ private T Initialize()
                 var changeToken = _dataSource.GetChangeToken();
                 _value = _initializeCore(_dataSource.Endpoints);
 
-                changeToken.RegisterChangeCallback(_initializerWithState, null);
+                // Don't resubscribe if we're already disposed.
+                if (_disposed)
+                {
+                    return _value;
+                }
+
+                _disposable = changeToken.RegisterChangeCallback(_initializerWithState, null);
                 return _value;
             }
         }
+
+        public void Dispose()
+        {
+            lock (_lock)
+            {
+                if (!_disposed)
+                {
+                    _disposable?.Dispose();
+                    _disposable = null;
+
+                    // Tracking whether we're disposed or not prevents a race-condition
+                    // between disposal and Initialize(). If a change callback fires after
+                    // we dispose, then we don't want to reregister.
+                    _disposed = true;
+                }
+            }
+        }
     }
 }

src/Http/Routing/src/DefaultLinkGenerator.cs

@@ -19,7 +19,7 @@
 
 namespace Microsoft.AspNetCore.Routing
 {
-    internal sealed class DefaultLinkGenerator : LinkGenerator
+    internal sealed class DefaultLinkGenerator : LinkGenerator, IDisposable
     {
         private readonly ParameterPolicyFactory _parameterPolicyFactory;
         private readonly ObjectPool<UriBuildingContext> _uriBuildingContextPool;
@@ -364,6 +364,11 @@ public static RouteValueDictionary GetAmbientValues(HttpContext httpContext)
             return httpContext?.Features.Get<IRouteValuesFeature>()?.RouteValues;
         }
 
+        public void Dispose()
+        {
+            _cache.Dispose();
+        }
+
         private static class Log
         {
             public static class EventIds

src/Http/Routing/src/DependencyInjection/RoutingServiceCollectionExtensions.cs

@@ -66,6 +66,7 @@ public static IServiceCollection AddRouting(this IServiceCollection services)
             services.TryAddSingleton<MatcherFactory, DfaMatcherFactory>();
             services.TryAddTransient<DfaMatcherBuilder>();
             services.TryAddSingleton<DfaGraphWriter>();
+            services.TryAddTransient<DataSourceDependentMatcher.Lifetime>();
 
             // Link generation related services
             services.TryAddSingleton<LinkGenerator, DefaultLinkGenerator>();
@@ -77,7 +78,6 @@ public static IServiceCollection AddRouting(this IServiceCollection services)
             //
             services.TryAddSingleton<EndpointSelector, DefaultEndpointSelector>();
             services.TryAddEnumerable(ServiceDescriptor.Singleton<MatcherPolicy, HttpMethodMatcherPolicy>());
-
             return services;
         }
 

src/Http/Routing/src/EndpointNameAddressScheme.cs

@@ -1,4 +1,4 @@
-// Copyright (c) .NET Foundation. All rights reserved.
+// 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;
@@ -9,7 +9,7 @@
 
 namespace Microsoft.AspNetCore.Routing
 {
-    internal class EndpointNameAddressScheme : IEndpointAddressScheme<string>
+    internal sealed class EndpointNameAddressScheme : IEndpointAddressScheme<string>, IDisposable
     {
         private readonly DataSourceDependentCache<Dictionary<string, Endpoint[]>> _cache;
 
@@ -103,5 +103,10 @@ string GetEndpointName(Endpoint endpoint)
                 return endpoint.Metadata.GetMetadata<IEndpointNameMetadata>()?.EndpointName;
             }
         }
+
+        public void Dispose()
+        {
+            _cache.Dispose();
+        }
     }
 }

src/Http/Routing/src/Matching/DataSourceDependentMatcher.cs

@@ -1,27 +1,31 @@
-// Copyright (c) .NET Foundation. All rights reserved.
+// 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;
 using System.Collections.Generic;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Http;
-using Microsoft.AspNetCore.Http.Features;
 
 namespace Microsoft.AspNetCore.Routing.Matching
 {
-    internal class DataSourceDependentMatcher : Matcher
+    internal sealed class DataSourceDependentMatcher : Matcher
     {
         private readonly Func<MatcherBuilder> _matcherBuilderFactory;
         private readonly DataSourceDependentCache<Matcher> _cache;
 
         public DataSourceDependentMatcher(
             EndpointDataSource dataSource,
+            Lifetime lifetime,
             Func<MatcherBuilder> matcherBuilderFactory)
         {
             _matcherBuilderFactory = matcherBuilderFactory;
 
             _cache = new DataSourceDependentCache<Matcher>(dataSource, CreateMatcher);
             _cache.EnsureInitialized();
+
+            // This will Dispose the cache when the lifetime is disposed, this allows
+            // the service provider to manage the lifetime of the cache.
+            lifetime.Cache = _cache;
         }
 
         // Used in tests
@@ -48,5 +52,41 @@ private Matcher CreateMatcher(IReadOnlyList<Endpoint> endpoints)
 
             return builder.Build();
         }
+
+        // Used to tie the lifetime of a DataSourceDependentCache to the service provider
+        public sealed class Lifetime : IDisposable
+        {
+            private readonly object _lock = new object();
+            private DataSourceDependentCache<Matcher> _cache;
+            private bool _disposed;
+
+            public DataSourceDependentCache<Matcher> Cache
+            {
+                get => _cache;
+                set
+                {
+                    lock (_lock)
+                    {
+                        if (_disposed)
+                        {
+                            value?.Dispose();
+                        }
+
+                        _cache = value;
+                    }
+                }
+            }
+
+            public void Dispose()
+            {
+                lock (_lock)
+                {
+                    _cache?.Dispose();
+                    _cache = null;
+
+                    _disposed = true;
+                }
+            }
+        }
     }
 }

src/Http/Routing/src/Matching/DfaMatcherFactory.cs

@@ -1,4 +1,4 @@
-// Copyright (c) .NET Foundation. All rights reserved.
+// 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;
@@ -29,7 +29,11 @@ public override Matcher CreateMatcher(EndpointDataSource dataSource)
                 throw new ArgumentNullException(nameof(dataSource));
             }
 
-            return new DataSourceDependentMatcher(dataSource, () =>
+            // Creates a tracking entry in DI to stop listening for change events
+            // when the services are disposed.
+            var lifetime = _services.GetRequiredService<DataSourceDependentMatcher.Lifetime>();
+
+            return new DataSourceDependentMatcher(dataSource, lifetime, () =>
             {
                 return _services.GetRequiredService<DfaMatcherBuilder>();
             });