Recreate cache of endpoints when data source updated (#503)

Addresses #454

src/Microsoft.AspNetCore.Dispatcher/CompositeDispatcherDataSource.cs

@@ -32,7 +32,7 @@ namespace Microsoft.AspNetCore.Dispatcher
 
         public override IChangeToken ChangeToken { get; }
 
-        protected override IReadOnlyList<Address> GetAddesses()
+        protected override IReadOnlyList<Address> GetAddresses()
         {
             var addresses = new List<Address>();
             for (var i = 0; i < _dataSources.Length; i++)

src/Microsoft.AspNetCore.Dispatcher/DefaultDispatcherDataSource.cs

@@ -24,7 +24,7 @@ namespace Microsoft.AspNetCore.Dispatcher
 
         public IList<Endpoint> Endpoints => _endpoints;
 
-        protected override IReadOnlyList<Address> GetAddesses() => _addresses;
+        protected override IReadOnlyList<Address> GetAddresses() => _addresses;
 
         protected override IReadOnlyList<Endpoint> GetEndpoints() => _endpoints;
     }

src/Microsoft.AspNetCore.Dispatcher/DispatcherDataSource.cs

@@ -10,11 +10,11 @@ namespace Microsoft.AspNetCore.Dispatcher
     {
         public abstract IChangeToken ChangeToken { get; }
 
-        protected abstract IReadOnlyList<Address> GetAddesses();
+        protected abstract IReadOnlyList<Address> GetAddresses();
 
         protected abstract IReadOnlyList<Endpoint> GetEndpoints();
 
-        IReadOnlyList<Address> IAddressCollectionProvider.Addresses => GetAddesses();
+        IReadOnlyList<Address> IAddressCollectionProvider.Addresses => GetAddresses();
 
         IReadOnlyList<Endpoint> IEndpointCollectionProvider.Endpoints => GetEndpoints();
     }

src/Microsoft.AspNetCore.Dispatcher/Tree/TreeMatcher.cs

@@ -3,7 +3,6 @@
 
 using System;
 using System.Collections.Generic;
-using System.Diagnostics;
 using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
@@ -12,11 +11,13 @@ using Microsoft.AspNetCore.Dispatcher.Patterns;
 using Microsoft.AspNetCore.Http;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Internal;
+using Primitives = Microsoft.Extensions.Primitives;
 
 namespace Microsoft.AspNetCore.Dispatcher
 {
     public class TreeMatcher : MatcherBase
     {
+        private bool _onChange;
         private bool _dataInitialized;
         private object _lock;
         private Cache _cache;
@@ -30,8 +31,6 @@ namespace Microsoft.AspNetCore.Dispatcher
             _initializer = CreateCache;
         }
 
-        public int Version { get; private set; }
-
         public override async Task MatchAsync(MatcherContext context)
         {
             if (context == null)
@@ -39,7 +38,7 @@ namespace Microsoft.AspNetCore.Dispatcher
                 throw new ArgumentNullException(nameof(context));
             }
 
-            EnsureServicesInitialized(context);
+            EnsureTreeMatcherServicesInitialized(context);
 
             var cache = LazyInitializer.EnsureInitialized(ref _cache, ref _dataInitialized, ref _lock, _initializer);
 
@@ -101,6 +100,24 @@ namespace Microsoft.AspNetCore.Dispatcher
             }
         }
 
+        private void EnsureTreeMatcherServicesInitialized(MatcherContext context)
+        {
+            EnsureServicesInitialized(context);
+            if (Volatile.Read(ref _onChange))
+            {
+                return;
+            }
+
+            lock (_lock)
+            {
+                if (!Volatile.Read(ref _onChange))
+                {
+                    _onChange = true;
+                    Primitives.ChangeToken.OnChange(() => ChangeToken, () => Volatile.Write(ref _dataInitialized, false));
+                }
+            }
+        }
+
         private bool MatchConstraints(HttpContext httpContext, DispatcherValueCollection values, IDictionary<string, IDispatcherValueConstraint> constraints)
         {
             if (constraints != null)
@@ -136,8 +153,7 @@ namespace Microsoft.AspNetCore.Dispatcher
             {
                 var endpoint = endpoints[i];
 
-                var templateEndpoint = endpoint as IRoutePatternEndpoint;
-                if (templateEndpoint == null)
+                if (!(endpoint is IRoutePatternEndpoint templateEndpoint))
                 {
                     continue;
                 }

test/Microsoft.AspNetCore.Dispatcher.Test/Tree/TreeMatcherTest.cs

@@ -1,12 +1,16 @@
 // 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.Linq;
+using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Http;
 using Microsoft.Extensions.Logging;
 using Microsoft.Extensions.Logging.Abstractions;
 using Microsoft.Extensions.Options;
+using Microsoft.Extensions.Primitives;
 using Moq;
 using Xunit;
 
@@ -776,6 +780,37 @@ namespace Microsoft.AspNetCore.Dispatcher
             Assert.Null(context.Endpoint);
         }
 
+        [Fact]
+        public async Task ChangeTokenTriggers_CreateCache()
+        {
+            // Arrange 1
+            var factory = new TreeMatcherFactory();
+            var dataSource = new TestDataSource(new List<Endpoint>() { new RoutePatternEndpoint("test/{p1}", new object(), Test_Delegate, "Test"), });
+            var matcher = factory.CreateMatcher(dataSource, new List<EndpointSelector>());
+            var context = CreateMatcherContext("/test/parameter1");
+
+            // Act 1
+            await matcher.MatchAsync(context);
+
+            // Assert 1
+            Assert.Equal("Test", context.Endpoint.DisplayName);
+            context.Values.TryGetValue("p1", out var value);
+            Assert.Equal("parameter1", value);
+
+            // Arrange 2
+            dataSource.UpdateEndpoints(new List<Endpoint>() { new RoutePatternEndpoint("test2/{p2}", new object(), Test_Delegate, "Test2"), });
+            context = CreateMatcherContext("/test2/parameter2");
+
+            // Act 2
+            await matcher.MatchAsync(context);
+
+            // Assert 2
+            Assert.Equal("Test2", context.Endpoint.DisplayName);
+            Assert.False(context.Values.TryGetValue("p1", out value));
+            context.Values.TryGetValue("p2", out value);
+            Assert.Equal("parameter2", value);
+        }
+
         private static MatcherContext CreateMatcherContext(string requestPath)
         {
             var request = new Mock<HttpRequest>(MockBehavior.Strict);
@@ -804,5 +839,66 @@ namespace Microsoft.AspNetCore.Dispatcher
         {
             return Task.CompletedTask;
         }
+
+        public class TestDataSource : DispatcherDataSource, IAddressCollectionProvider, IEndpointCollectionProvider
+        {
+            private IList<Address> _addresses;
+            private IList<Endpoint> _endpoints;
+            private TestChangeToken _changeToken;
+            private readonly object _lock = new object();
+
+            public TestDataSource(IList<Endpoint> endpoints)
+            {
+                _addresses = new List<Address>();
+                _endpoints = endpoints;
+                _changeToken = new TestChangeToken();
+            }
+
+            public void UpdateEndpoints(IList<Endpoint> endpoints)
+            {
+                lock (_lock)
+                {
+                    _endpoints = endpoints;
+                    // Trigger change token here
+                    var previousToken = _changeToken;
+                    _changeToken = new TestChangeToken();
+                    previousToken.OnChange();
+                }
+            }
+
+            public override IChangeToken ChangeToken
+            {
+                get
+                {
+                    lock (_lock)
+                    {
+                        return _changeToken;
+                    }
+                }
+            }
+
+            IReadOnlyList<Address> IAddressCollectionProvider.Addresses => GetAddresses();
+
+            IReadOnlyList<Endpoint> IEndpointCollectionProvider.Endpoints => GetEndpoints();
+
+            protected override IReadOnlyList<Address> GetAddresses() => _addresses.ToList();
+
+            protected override IReadOnlyList<Endpoint> GetEndpoints() => _endpoints.ToList();
+
+            public IList<Endpoint> Endpoints => _endpoints;
+
+            private class TestChangeToken : IChangeToken
+            {
+                private CancellationTokenSource _cts = new CancellationTokenSource();
+
+                public bool HasChanged => true;
+
+                public bool ActiveChangeCallbacks => true;
+
+                public IDisposable RegisterChangeCallback(Action<object> callback, object state) => _cts.Token.Register(callback, state);
+
+                public void OnChange() => _cts.Cancel();
+            }
+        }
     }
 }