Building out caching

Passing along signal of VPP file monitoring
Expiring results as appropriate in AvailableExtensions

--HG--
branch : dev

src/Orchard.Tests/Caching/CacheScopeTests.cs

@@ -0,0 +1,47 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using NUnit.Framework;
+using Orchard.Caching;
+using Orchard.Environment;
+using Autofac;
+using Orchard.Environment.FileSystems;
+using Orchard.Services;
+
+namespace Orchard.Tests.Caching {
+    [TestFixture]
+    public class CacheScopeTests {
+        private IContainer _hostContainer;
+
+        [SetUp]
+        public void Init() {
+            _hostContainer = OrchardStarter.CreateHostContainer(builder => {
+                builder.RegisterType<Alpha>().InstancePerDependency();
+            });
+
+        }
+
+        public class Alpha {
+            public ICacheManager CacheManager { get; set; }
+
+            public Alpha(ICacheManager cacheManager) {
+                CacheManager = cacheManager;
+            }
+        }
+
+        [Test]
+        public void ComponentsAtHostLevelHaveAccessToCache() {
+            var alpha = _hostContainer.Resolve<Alpha>();
+            Assert.That(alpha.CacheManager, Is.Not.Null);            
+        }
+
+        [Test]
+        public void HostLevelHasAccessToGlobalVolatileProviders() {
+            Assert.That(_hostContainer.Resolve<IVirtualPathProvider>(), Is.Not.Null);            
+            Assert.That(_hostContainer.Resolve<IAppDataFolder>(), Is.Not.Null);            
+            Assert.That(_hostContainer.Resolve<IClock>(), Is.Not.Null);            
+        }
+
+    }
+}

src/Orchard.Tests/Caching/CacheTests.cs

@@ -1,4 +1,5 @@
-using Autofac;
+using System;
+using Autofac;
 using NUnit.Framework;
 using Orchard.Caching;
 
@@ -11,9 +12,12 @@ namespace Orchard.Tests.Caching {
         [SetUp]
         public void Init() {
             var builder = new ContainerBuilder();
+            builder.RegisterModule(new CacheModule());
+            builder.RegisterType<DefaultCacheManager>().As<ICacheManager>();
+            builder.RegisterType<DefaultCacheHolder>().As<ICacheHolder>().SingleInstance();
             builder.RegisterType<DefaultCacheManager>().As<ICacheManager>();
             _container = builder.Build();
-            _cacheManager = _container.Resolve<ICacheManager>();
+            _cacheManager = _container.Resolve<ICacheManager>(new TypedParameter(typeof(Type), GetType()));
         }
 
         [Test]
@@ -28,5 +32,66 @@ namespace Orchard.Tests.Caching {
             var result = _cacheManager.Get("testItem", ctx => "");
             Assert.That(result, Is.EqualTo("testResult"));
         }
+
+        [Test]
+        public void CacheModuleProvidesTypeSpecificManager() {
+            var scope = _container.BeginLifetimeScope(builder => {
+                builder.RegisterModule(new CacheModule());
+                builder.RegisterType<ComponentOne>();
+                builder.RegisterType<ComponentTwo>();
+            });
+
+            var c1 = scope.Resolve<ComponentOne>();
+            var c2 = scope.Resolve<ComponentTwo>();
+            var w1a = c1.CacheManager.Get("hello", ctx => "world1");
+            var w1b = c1.CacheManager.Get("hello", ctx => "world2");
+            var w2a = c2.CacheManager.Get("hello", ctx => "world3");
+            var w2b = c2.CacheManager.Get("hello", ctx => "world4");
+
+            Assert.That(w1a, Is.EqualTo("world1"));
+            Assert.That(w1b, Is.EqualTo("world1"));
+            Assert.That(w2a, Is.EqualTo("world3"));
+            Assert.That(w2b, Is.EqualTo("world3"));
+
+            var c3 = scope.Resolve<ComponentOne>();
+            var c4 = scope.Resolve<ComponentTwo>();
+            var w3a = c3.CacheManager.Get("hello", ctx => "world5");
+            var w3b = c3.CacheManager.Get("hello", ctx => "world6");
+            var w4a = c4.CacheManager.Get("hello", ctx => "world7");
+            var w4b = c4.CacheManager.Get("hello", ctx => "world8");
+
+            Assert.That(w3a, Is.EqualTo("world1"));
+            Assert.That(w3b, Is.EqualTo("world1"));
+            Assert.That(w4a, Is.EqualTo("world3"));
+            Assert.That(w4b, Is.EqualTo("world3"));
+
+            Assert.That(c1.CacheManager,
+                Is.Not.SameAs(c3.CacheManager));
+
+            Assert.That(c1.CacheManager.GetCache<string, string>(),
+                Is.SameAs(c3.CacheManager.GetCache<string, string>()));
+
+            Assert.That(c1.CacheManager,
+                Is.Not.SameAs(c2.CacheManager));
+
+            Assert.That(c1.CacheManager.GetCache<string, string>(),
+                Is.Not.SameAs(c2.CacheManager.GetCache<string, string>()));
+        }
+
+        class ComponentOne {
+            public ICacheManager CacheManager { get; set; }
+
+            public ComponentOne(ICacheManager cacheManager) {
+                CacheManager = cacheManager;
+            }
+        }
+
+        class ComponentTwo {
+            public ICacheManager CacheManager { get; set; }
+
+            public ComponentTwo(ICacheManager cacheManager) {
+                CacheManager = cacheManager;
+            }
+        }
     }
-}
+}

src/Orchard.Tests/Environment/Configuration/AppDataFolderTests.cs

@@ -1,7 +1,6 @@
 using System.IO;
 using System.Linq;
 using NUnit.Framework;
-using Orchard.Environment.Configuration;
 using Orchard.Environment.FileSystems;
 
 namespace Orchard.Tests.Environment.Configuration {

src/Orchard.Tests/Environment/Configuration/DefaultTenantManagerTests.cs

@@ -3,6 +3,7 @@ using System.Linq;
 using Moq;
 using NUnit.Framework;
 using Orchard.Environment.Configuration;
+using Orchard.Environment.FileSystems;
 
 namespace Orchard.Tests.Environment.Configuration {
     [TestFixture]

src/Orchard.Tests/Environment/Topology/DefaultShellDescriptorCacheTests.cs

@@ -3,7 +3,6 @@ using System.Runtime.Serialization;
 using System.Xml;
 using Autofac;
 using NUnit.Framework;
-using Orchard.Environment.Configuration;
 using Orchard.Environment.FileSystems;
 using Orchard.Environment.Topology;
 using Orchard.Environment.Topology.Models;

src/Orchard.Tests/Orchard.Framework.Tests.csproj

@@ -125,6 +125,7 @@
     </Reference>
   </ItemGroup>
   <ItemGroup>
+    <Compile Include="Caching\CacheScopeTests.cs" />
     <Compile Include="Caching\CacheTests.cs" />
     <Compile Include="Commands\CommandHandlerDescriptorBuilderTests.cs" />
     <Compile Include="Commands\CommandHandlerTests.cs" />

src/Orchard.Tests/Stubs/StubClock.cs

@@ -16,5 +16,6 @@ namespace Orchard.Tests.Stubs {
         public DateTime FutureMoment(TimeSpan span) {
             return UtcNow.Add(span);
         }
+
     }
 }

src/Orchard.Web/Orchard.Web.csproj

@@ -393,7 +393,7 @@
         <WebProjectProperties>
           <UseIIS>False</UseIIS>
           <AutoAssignPort>False</AutoAssignPort>
-          <DevelopmentServerPort>80</DevelopmentServerPort>
+          <DevelopmentServerPort>30320</DevelopmentServerPort>
           <DevelopmentServerVPath>/</DevelopmentServerVPath>
           <IISUrl>
           </IISUrl>

src/Orchard/Caching/AcquireContext.cs

@@ -1,14 +1,13 @@
 using System;
-using Orchard.Caching.Providers;
 
 namespace Orchard.Caching {
     public class AcquireContext<TKey> {
-        public AcquireContext(TKey key, Action<IVolatileSignal> monitor) {
+        public AcquireContext(TKey key, Action<IVolatileToken> monitor) {
             Key = key;
-            IsInvalid = monitor;
+            Monitor = monitor;
         }
 
         public TKey Key { get; private set; }
-        public Action<IVolatileSignal> IsInvalid { get; private set; }
+        public Action<IVolatileToken> Monitor { get; private set; }
     }
 }

src/Orchard/Caching/Cache.cs

@@ -1,6 +1,6 @@
 using System;
 using System.Collections.Generic;
-using Orchard.Caching.Providers;
+using System.Linq;
 
 namespace Orchard.Caching {
     public class Cache<TKey, TResult> : ICache<TKey, TResult> {
@@ -12,19 +12,19 @@ namespace Orchard.Caching {
 
         public TResult Get(TKey key, Func<AcquireContext<TKey>, TResult> acquire) {
             CacheEntry entry;
-            if (!_entries.TryGetValue(key, out entry)) {
-                entry = new CacheEntry { VolatileItems = new List<IVolatileSignal>() };
+            if (!_entries.TryGetValue(key, out entry) || entry.Tokens.Any(t => !t.IsCurrent)) {
+                entry = new CacheEntry { Tokens = new List<IVolatileToken>() };
 
-                var context = new AcquireContext<TKey>(key, volatileItem => entry.VolatileItems.Add(volatileItem));
+                var context = new AcquireContext<TKey>(key, volatileItem => entry.Tokens.Add(volatileItem));
                 entry.Result = acquire(context);
-                _entries.Add(key, entry);
+                _entries[key] = entry;
             }
             return entry.Result;
         }
 
         private class CacheEntry {
             public TResult Result { get; set; }
-            public IList<IVolatileSignal> VolatileItems { get; set; }
+            public IList<IVolatileToken> Tokens { get; set; }
         }
     }
 

src/Orchard/Caching/CacheModule.cs

@@ -0,0 +1,29 @@
+using System;
+using System.Linq;
+using Autofac;
+
+namespace Orchard.Caching {
+    public class CacheModule : Module {
+        protected override void Load(ContainerBuilder builder) {
+            builder.RegisterType<DefaultCacheManager>()
+                .As<ICacheManager>()
+                .InstancePerDependency();
+        }
+
+        protected override void AttachToComponentRegistration(Autofac.Core.IComponentRegistry componentRegistry, Autofac.Core.IComponentRegistration registration) {
+            var needsCacheManager = registration.Activator.LimitType
+                .GetConstructors()
+                .Any(x => x.GetParameters()
+                    .Any(xx => xx.ParameterType == typeof(ICacheManager)));
+
+            if (needsCacheManager) {
+                registration.Preparing += (sender, e) => {                    
+                    var parameter = new TypedParameter(
+                        typeof(ICacheManager),
+                        e.Context.Resolve<ICacheManager>(new TypedParameter(typeof(Type), registration.Activator.LimitType)));
+                    e.Parameters = e.Parameters.Concat(new[] { parameter });
+                };
+            }
+        }
+    }
+}

src/Orchard/Caching/DefaultCacheHolder.cs

@@ -0,0 +1,27 @@
+using System;
+using System.Collections.Generic;
+using Castle.Core;
+
+namespace Orchard.Caching {
+    public class DefaultCacheHolder : ICacheHolder {
+        private readonly IDictionary<CacheKey, object> _caches = new Dictionary<CacheKey, object>();
+
+        class CacheKey : Pair<Type, Pair<Type, Type>> {
+            public CacheKey(Type component, Type key, Type result)
+                : base(component, new Pair<Type, Type>(key, result)) {
+            }
+        }
+
+        public ICache<TKey, TResult> GetCache<TKey, TResult>(Type component) {
+            var cacheKey = new CacheKey(component, typeof(TKey), typeof(TResult));
+            lock (_caches) {
+                object value;
+                if (!_caches.TryGetValue(cacheKey, out value)) {
+                    value = new Cache<TKey, TResult>();
+                    _caches[cacheKey] = value;
+                }
+                return (ICache<TKey, TResult>)value;
+            }
+        }
+    }
+}

src/Orchard/Caching/DefaultCacheManager.cs

@@ -1,32 +1,21 @@
 using System;
-using System.Collections.Generic;
-using Castle.Core;
 
 namespace Orchard.Caching {
     public class DefaultCacheManager : ICacheManager {
-        private readonly Dictionary<Pair<Type, Type>, object> _caches;
+        private readonly Type _component;
+        private readonly ICacheHolder _cacheHolder;
 
-        public DefaultCacheManager() {
-            _caches = new Dictionary<Pair<Type, Type>, object>();
+        public DefaultCacheManager(Type component, ICacheHolder cacheHolder) {
+            _component = component;
+            _cacheHolder = cacheHolder;
         }
 
-        #region Implementation of ICacheManager
+        public ICache<TKey, TResult> GetCache<TKey, TResult>() {
+            return _cacheHolder.GetCache<TKey, TResult>(_component);
+        }
 
         public TResult Get<TKey, TResult>(TKey key, Func<AcquireContext<TKey>, TResult> acquire) {
             return GetCache<TKey, TResult>().Get(key, acquire);
         }
-
-        public ICache<TKey, TResult> GetCache<TKey, TResult>() {
-            var cacheKey = new Pair<Type, Type>(typeof(TKey), typeof(TResult));
-            object value;
-            if (!_caches.TryGetValue(cacheKey, out value)) {
-                value = new Cache<TKey, TResult>();
-                _caches.Add(cacheKey, value);
-            }
-
-            return (ICache<TKey, TResult>)value;
-        }
-
-        #endregion
     }
 }

src/Orchard/Caching/ICacheHolder.cs

@@ -0,0 +1,7 @@
+using System;
+
+namespace Orchard.Caching {
+    public interface ICacheHolder : ISingletonDependency {
+        ICache<TKey, TResult> GetCache<TKey, TResult>(Type component);
+    }
+}

src/Orchard/Caching/ICacheManager.cs

@@ -1,7 +1,7 @@
 using System;
 
 namespace Orchard.Caching {
-    public interface ICacheManager : ISingletonDependency {
+    public interface ICacheManager {
         TResult Get<TKey, TResult>(TKey key, Func<AcquireContext<TKey>, TResult> acquire);
         ICache<TKey, TResult> GetCache<TKey, TResult>();
     }

src/Orchard/Caching/IVolatileProvider.cs

@@ -0,0 +1,4 @@
+namespace Orchard.Caching {
+    public interface IVolatileProvider : ISingletonDependency {
+    }
+}

src/Orchard/Caching/IVolatileToken.cs

@@ -0,0 +1,5 @@
+namespace Orchard.Caching {
+    public interface IVolatileToken {
+        bool IsCurrent { get; }
+    }
+}

src/Orchard/Caching/Providers/IVolatileProvider.cs

@@ -1,5 +0,0 @@
-namespace Orchard.Caching.Providers {
-    public interface IVolatileProvider : IDependency {
-        void Enlist(IVolatileSink sink);
-    }
-}

src/Orchard/Caching/Providers/IVolatileSignal.cs

@@ -1,5 +0,0 @@
-namespace Orchard.Caching.Providers {
-    public interface IVolatileSignal {
-        IVolatileProvider Provider { get; set; }
-    }
-}

src/Orchard/Caching/Providers/IVolatileSink.cs

@@ -1,5 +0,0 @@
-namespace Orchard.Caching.Providers {
-    public interface IVolatileSink {
-
-    }
-}

src/Orchard/Caching/Weak.cs

@@ -0,0 +1,23 @@
+using System;
+using System.Runtime.Serialization;
+
+namespace Orchard.Caching {
+    public class Weak<T> : WeakReference {
+        public Weak(T target)
+            : base(target) {
+        }
+
+        public Weak(T target, bool trackResurrection)
+            : base(target, trackResurrection) {
+        }
+
+        protected Weak(SerializationInfo info, StreamingContext context)
+            : base(info, context) {
+        }
+
+        public new T Target {
+            get { return (T)base.Target; }
+            set { base.Target = value; }
+        }
+    }
+}

src/Orchard/Environment/Extensions/Folders/ExtensionFolders.cs

@@ -24,7 +24,7 @@ namespace Orchard.Environment.Extensions.Folders {
         private readonly ICacheManager _cacheManager;
         private readonly IVirtualPathProvider _virtualPathProvider;
 
-        public ExtensionFolders(
+        protected ExtensionFolders(
             IEnumerable<string> paths,
             string manifestName,
             bool manifestIsOptional,
@@ -39,28 +39,39 @@ namespace Orchard.Environment.Extensions.Folders {
         }
 
         public IEnumerable<ExtensionDescriptor> AvailableExtensions() {
-            var virtualPaths = _cacheManager.Get("", ctx => {
-                var x = 5;
-                return new[] { "hello" };
-            });
-
-
             var list = new List<ExtensionDescriptor>();
-            foreach (var virtualPath in virtualPaths) {
-                list.Add(GetExtensionDescriptor(virtualPath));
+            foreach (var locationPath in _paths) {
+                var subfolderPaths = _cacheManager.Get(locationPath, ctx => {
+                    ctx.Monitor(_virtualPathProvider.WhenPathChanges(ctx.Key));
+                    return _virtualPathProvider.GetSubfolderPaths(ctx.Key);
+                });
+                foreach (var subfolderPath in subfolderPaths) {
+                    var extensionName = Path.GetFileName(subfolderPath.TrimEnd('/', '\\'));
+                    var manifestPath = Path.Combine(subfolderPath, _manifestName);
+                    var descriptor = GetExtensionDescriptor(locationPath, extensionName, manifestPath);
+                    if (descriptor != null)
+                        list.Add(descriptor);
+                }
             }
             return list;
         }
 
-        ExtensionDescriptor GetExtensionDescriptor(string virtualPath) {
-            return _cacheManager.Get(virtualPath, context => {
+        ExtensionDescriptor GetExtensionDescriptor(string locationPath, string extensionName, string manifestPath) {
+            return _cacheManager.Get(manifestPath, context => {
 
-                context.IsInvalid(_virtualPathProvider.WhenPathChanges(virtualPath));
+                context.Monitor(_virtualPathProvider.WhenPathChanges(manifestPath));
 
-                var text = _virtualPathProvider.ReadAllText(virtualPath);
+                var manifestText = _virtualPathProvider.ReadAllText(manifestPath);
+                if (manifestText == null) {
+                    if (_manifestIsOptional) {
+                        manifestText = string.Format("name: {0}", extensionName);
+                    }
+                    else {
+                        return null;
+                    }
+                }
 
-                var parseResult = ParseManifest(text);
-                return GetDescriptorForExtension(parseResult.Name, parseResult);
+                return GetDescriptorForExtension(locationPath, extensionName, ParseManifest(manifestText));
             });
         }
 
@@ -78,52 +89,29 @@ namespace Orchard.Environment.Extensions.Folders {
         }
 
         public ParseResult ParseManifest(string name) {
-            foreach (var path in _paths) {
-                if (!Directory.Exists(PathHelpers.GetPhysicalPath(path)))
-                    continue;
-
-                var extensionDirectoryPath = Path.Combine(PathHelpers.GetPhysicalPath(path), name);
-                if (!Directory.Exists(PathHelpers.GetPhysicalPath(extensionDirectoryPath)))
-                    continue;
-
-                var extensionManifestPath = Path.Combine(extensionDirectoryPath, _manifestName);
-
-                if (File.Exists(extensionManifestPath)) {
-                    var yamlStream = YamlParser.Load(extensionManifestPath);
-                    return new ParseResult {
-                        Location = path,
-                        Name = name,
-                        YamlDocument = yamlStream.Documents.Single()
-                    };
-                }
-
-                if (_manifestIsOptional) {
-                    var yamlInput = new TextInput(string.Format("name: {0}", name));
-                    var parser = new YamlParser();
-                    bool success;
-                    var yamlStream = parser.ParseYamlStream(yamlInput, out success);
-                    return new ParseResult {
-                        Location = path,
-                        Name = name,
-                        YamlDocument = yamlStream.Documents.Single()
-                    };
-                }
+            bool success;
+            var yamlStream = new YamlParser().ParseYamlStream(new TextInput(name), out success);
+            if (yamlStream == null || !success) {
+                return null;
             }
-            return null;
+            return new ParseResult {
+                Name = name,
+                YamlDocument = yamlStream.Documents.Single()
+            };
         }
 
 
-        private ExtensionDescriptor GetDescriptorForExtension(string name, ParseResult parseResult) {
+        private ExtensionDescriptor GetDescriptorForExtension(string locationPath, string extensionName, ParseResult parseResult) {
             var mapping = (Mapping)parseResult.YamlDocument.Root;
             var fields = mapping.Entities
                 .Where(x => x.Key is Scalar)
                 .ToDictionary(x => ((Scalar)x.Key).Text, x => x.Value);
 
             var extensionDescriptor = new ExtensionDescriptor {
-                Location = parseResult.Location,
-                Name = name,
+                Location = locationPath,
+                Name = extensionName,
                 ExtensionType = _extensionType,
-                DisplayName = GetValue(fields, "name") ?? name,
+                DisplayName = GetValue(fields, "name") ?? extensionName,
                 Description = GetValue(fields, "description"),
                 Version = GetValue(fields, "version"),
                 OrchardVersion = GetValue(fields, "orchardversion"),

src/Orchard/Environment/FileSystems/AppDataFolder.cs

@@ -1,11 +1,9 @@
-using System;
-using System.Collections.Generic;
+using System.Collections.Generic;
 using System.IO;
 using System.Linq;
 using System.Web.Hosting;
-using Orchard.Environment.FileSystems;
 
-namespace Orchard.Environment.Configuration {
+namespace Orchard.Environment.FileSystems {
     public class AppDataFolder : IAppDataFolder {
         protected string _basePath;
 
@@ -42,9 +40,9 @@ namespace Orchard.Environment.Configuration {
             var files = Directory.GetFiles(directoryPath);
 
             return files.Select(file => {
-                var fileName = Path.GetFileName(file);
-                return Path.Combine(path, fileName);
-            });
+                                    var fileName = Path.GetFileName(file);
+                                    return Path.Combine(path, fileName);
+                                });
         }
 
         public IEnumerable<string> ListDirectories(string path) {
@@ -55,9 +53,9 @@ namespace Orchard.Environment.Configuration {
             var files = Directory.GetDirectories(directoryPath);
 
             return files.Select(file => {
-                var fileName = Path.GetFileName(file);
-                return Path.Combine(path, fileName);
-            });
+                                    var fileName = Path.GetFileName(file);
+                                    return Path.Combine(path, fileName);
+                                });
         }
 
         public string CreateDirectory(string path) {
@@ -74,5 +72,6 @@ namespace Orchard.Environment.Configuration {
         public string MapPath(string path) {
             return Path.Combine(_basePath, path);
         }
+
     }
-}
+}

src/Orchard/Environment/FileSystems/DefaultVirtualPathProvider.cs

@@ -1,54 +1,127 @@
 using System;
 using System.Collections.Generic;
 using System.IO;
+using System.Linq;
+using System.Web.Caching;
 using System.Web.Hosting;
-using Orchard.Caching.Providers;
+using Orchard.Caching;
 using Orchard.Services;
 
 namespace Orchard.Environment.FileSystems {
     public class DefaultVirtualPathProvider : IVirtualPathProvider {
         private readonly IClock _clock;
-        private readonly IList<IVolatileSink> _sinks = new List<IVolatileSink>();
-        //private string _cachePrefix = Guid.NewGuid().ToString("n");
+        private readonly Thunk _thunk;
+        private readonly string _prefix = Guid.NewGuid().ToString("n");
+        private readonly IDictionary<string, Weak<Token>> _tokens = new Dictionary<string, Weak<Token>>();
+
 
         public DefaultVirtualPathProvider(IClock clock) {
             _clock = clock;
+            _thunk = new Thunk(this);
+        }
+
+        public IEnumerable<string> GetSubfolderPaths(string virtualPath) {
+            if (!HostingEnvironment.VirtualPathProvider.DirectoryExists(virtualPath))
+                return Enumerable.Empty<string>();
+
+            return HostingEnvironment.VirtualPathProvider
+                .GetDirectory(virtualPath)
+                .Directories.OfType<VirtualDirectory>()
+                .Select(d => d.VirtualPath)
+                .ToArray();
         }
 
         public string ReadAllText(string virtualPath) {
+            if (!HostingEnvironment.VirtualPathProvider.FileExists(virtualPath))
+                return null;
+
             using (var stream = VirtualPathProvider.OpenFile(virtualPath)) {
                 using (var reader = new StreamReader(stream)) {
                     return reader.ReadToEnd();
                 }
             }
-            //var cd = HostingEnvironment.VirtualPathProvider.. .GetCacheDependency(virtualPath, null, _clock.UtcNow);
-            //HostingEnvironment.Cache.Add(
-            //    _cachePrefix + virtualPath,
-            //    virtualPath,
-            //    cd,
-            //    NoAbsoluteExpiration,
-            //    );
         }
 
-        public IVolatileSignal WhenPathChanges(string virtualPath) {
-
-            return new VirtualPathSignal(this, virtualPath);
+        public IVolatileToken WhenPathChanges(string virtualPath) {
+            var token = BindToken(virtualPath);
+            BindSignal(virtualPath);
+            return token;
         }
 
+        private Token BindToken(string virtualPath) {
+            lock (_tokens) {
+                Weak<Token> weak;
+                if (!_tokens.TryGetValue(virtualPath, out weak)) {
+                    weak = new Weak<Token>(new Token(virtualPath));
+                    _tokens[virtualPath] = weak;
+                }
 
-        class VirtualPathSignal : IVolatileSignal {
-            private readonly string _virtualPath;
+                var token = weak.Target;
+                if (token == null) {
+                    token = new Token(virtualPath);
+                    weak.Target = token;
+                }
 
-            public VirtualPathSignal(DefaultVirtualPathProvider provider, string virtualPath) {
-                _virtualPath = virtualPath;
-                Provider = provider;
+                return token;
+            }
+        }
+
+        private Token DetachToken(string virtualPath) {
+            lock (_tokens) {
+                Weak<Token> weak;
+                if (!_tokens.TryGetValue(virtualPath, out weak)) {
+                    return null;
+                }
+                var token = weak.Target;
+                weak.Target = null;
+                return token;
+            }
+        }
+
+        private void BindSignal(string virtualPath) {
+            var cacheDependency = HostingEnvironment.VirtualPathProvider.GetCacheDependency(
+                virtualPath,
+                new[] { virtualPath },
+                _clock.UtcNow);
+
+            HostingEnvironment.Cache.Add(
+                _prefix + virtualPath,
+                virtualPath,
+                cacheDependency,
+                Cache.NoAbsoluteExpiration,
+                Cache.NoSlidingExpiration,
+                CacheItemPriority.NotRemovable,
+                _thunk.Signal);
+        }
+
+        public void Signal(string key, object value, CacheItemRemovedReason reason) {
+            var virtualPath = Convert.ToString(value);
+            var token = DetachToken(virtualPath);
+            if (token != null)
+                token.IsCurrent = false;
+        }
+
+        public class Token : IVolatileToken {
+            public Token(string virtualPath) {
+                IsCurrent = true;
+                VirtualPath = virtualPath;
+            }
+            public bool IsCurrent { get; set; }
+            public string VirtualPath { get; private set; }
+        }
+
+        class Thunk {
+            private readonly Weak<DefaultVirtualPathProvider> _weak;
+
+            public Thunk(DefaultVirtualPathProvider provider) {
+                _weak = new Weak<DefaultVirtualPathProvider>(provider);
             }
 
-            public IVolatileProvider Provider { get; set; }
-        }
-
-        public void Enlist(IVolatileSink sink) {
-            _sinks.Add(sink);
+            public void Signal(string key, object value, CacheItemRemovedReason reason) {
+                var provider = _weak.Target;
+                if (provider != null)
+                    provider.Signal(key, value, reason);
+            }
         }
     }
 }

src/Orchard/Environment/FileSystems/IAppDataFolder.cs

@@ -1,4 +1,5 @@
 using System.Collections.Generic;
+using Orchard.Caching;
 
 namespace Orchard.Environment.FileSystems {
     /// <summary>
@@ -6,7 +7,7 @@ namespace Orchard.Environment.FileSystems {
     /// Expected to work on physical filesystem, but decouples core
     /// system from web hosting apis
     /// </summary>
-    public interface IAppDataFolder {
+    public interface IAppDataFolder : IVolatileProvider {
         IEnumerable<string> ListFiles(string path);
         IEnumerable<string> ListDirectories(string path);
 

src/Orchard/Environment/FileSystems/IVirtualPathProvider.cs

@@ -1,9 +1,11 @@
-using Orchard.Caching.Providers;
+using System.Collections.Generic;
+using Orchard.Caching;
 
 namespace Orchard.Environment.FileSystems {
     public interface IVirtualPathProvider : IVolatileProvider {
-        IVolatileSignal WhenPathChanges(string path);
-
+        IEnumerable<string> GetSubfolderPaths(string virtualPath);
         string ReadAllText(string virtualPath);
+
+        IVolatileToken WhenPathChanges(string path);
     }
-}
+}

src/Orchard/Environment/OrchardStarter.cs

@@ -5,6 +5,7 @@ using System.Web.Hosting;
 using Autofac;
 using Autofac.Configuration;
 using Autofac.Integration.Web;
+using Orchard.Caching;
 using Orchard.Environment.AutofacUtil;
 using Orchard.Environment.Configuration;
 using Orchard.Environment.Extensions;
@@ -15,6 +16,7 @@ using Orchard.Environment.ShellBuilders;
 using Orchard.Environment.Topology;
 using Orchard.Events;
 using Orchard.Logging;
+using Orchard.Services;
 
 namespace Orchard.Environment {
     public static class OrchardStarter {
@@ -22,10 +24,15 @@ namespace Orchard.Environment {
             var builder = new ContainerBuilder();
             builder.RegisterModule(new LoggingModule());
             builder.RegisterModule(new EventsModule());
+            builder.RegisterModule(new CacheModule());
 
             // a single default host implementation is needed for bootstrapping a web app domain
             builder.RegisterType<DefaultOrchardEventBus>().As<IEventBus>().SingleInstance();
-            builder.RegisterType<AppDataFolder>().As<IAppDataFolder>().SingleInstance();
+            builder.RegisterType<DefaultCacheHolder>().As<ICacheHolder>().SingleInstance();
+
+            RegisterVolatileProvider<DefaultVirtualPathProvider, IVirtualPathProvider>(builder);
+            RegisterVolatileProvider<AppDataFolder, IAppDataFolder>(builder);
+            RegisterVolatileProvider<Clock, IClock>(builder);
 
             builder.RegisterType<DefaultOrchardHost>().As<IOrchardHost>().As<IEventHandler>().SingleInstance();
             {
@@ -92,6 +99,13 @@ namespace Orchard.Environment {
             return builder.Build();
         }
 
+        private static void RegisterVolatileProvider<TRegister, TService>(ContainerBuilder builder) where TService : IVolatileProvider {
+            builder.RegisterType<TRegister>()
+                .As<TService>()
+                .As<IVolatileProvider>()
+                .SingleInstance();
+        }
+
         public static IOrchardHost CreateHost(Action<ContainerBuilder> registrations) {
             var container = CreateHostContainer(registrations);
             return container.Resolve<IOrchardHost>();

src/Orchard/IDependency.cs

@@ -5,6 +5,7 @@
     public interface ISingletonDependency : IDependency {
         
     }
+
     public interface ITransientDependency : IDependency {
 
     }

src/Orchard/Orchard.Framework.csproj

@@ -145,15 +145,18 @@
   <ItemGroup>
     <Compile Include="Caching\AcquireContext.cs" />
     <Compile Include="Caching\Cache.cs" />
+    <Compile Include="Caching\CacheModule.cs" />
+    <Compile Include="Caching\DefaultCacheHolder.cs" />
     <Compile Include="Caching\DefaultCacheManager.cs" />
-    <Compile Include="Caching\Providers\IVolatileSink.cs" />
+    <Compile Include="Caching\ICacheHolder.cs" />
+    <Compile Include="Caching\Weak.cs" />
     <Compile Include="Environment\FileSystems\DefaultVirtualPathProvider.cs" />
     <Compile Include="Environment\FileSystems\IAppDataFolder.cs" />
     <Compile Include="Environment\FileSystems\IVirtualPathProvider.cs" />
     <Compile Include="Caching\ICache.cs" />
     <Compile Include="Caching\ICacheManager.cs" />
-    <Compile Include="Caching\Providers\IVolatileSignal.cs" />
-    <Compile Include="Caching\Providers\IVolatileProvider.cs" />
+    <Compile Include="Caching\IVolatileToken.cs" />
+    <Compile Include="Caching\IVolatileProvider.cs" />
     <Compile Include="Commands\CommandParameters.cs" />
     <Compile Include="Commands\CommandDescriptor.cs" />
     <Compile Include="Commands\CommandHandlerDescriptor.cs" />

src/Orchard/Services/Clock.cs

@@ -1,13 +1,15 @@
 using System;
+using Orchard.Caching;
 
 namespace Orchard.Services {
-    public interface IClock : IDependency {
+    public interface IClock : IVolatileProvider {
         DateTime UtcNow { get; }
     }
 
     public class Clock : IClock {
         public DateTime UtcNow {
-            get { return DateTime.Now; }
+            get { return DateTime.UtcNow; }
         }
+
     }
 }