Add version tracking to manage cache expiration.

Author: tillig

src/Autofac/Core/Registration/ComponentRegistry.cs

@@ -16,7 +16,7 @@ namespace Autofac.Core.Registration;
 /// is normally used through a <see cref="ContainerBuilder"/>, and not
 /// directly by application code.
 /// </remarks>
-internal class ComponentRegistry : Disposable, IComponentRegistry
+internal class ComponentRegistry : Disposable, IComponentRegistry, IRegistrationDiagnostics
 {
     private readonly IRegisteredServicesTracker _registeredServicesTracker;
 
@@ -62,6 +62,9 @@ internal ComponentRegistry(IRegisteredServicesTracker registeredServicesTracker,
     /// registrations for a new customized scope.</remarks>
     public bool HasLocalComponents => true;
 
+    /// <inheritdoc/>
+    int IRegistrationDiagnostics.RegistrationsVersion => _registeredServicesTracker.RegistrationsVersion;
+
     /// <summary>
     /// Attempts to find a default registration for the specified service.
     /// </summary>

src/Autofac/Core/Registration/DefaultRegisteredServicesTracker.cs

@@ -5,6 +5,7 @@
 using System.Reflection;
 using System.Runtime.CompilerServices;
 using Autofac.Core.Resolving.Pipeline;
+using Autofac.Diagnostics;
 using Autofac.Util;
 using Autofac.Util.Cache;
 
@@ -50,6 +51,7 @@ internal class DefaultRegisteredServicesTracker : Disposable, IRegisteredService
 
     private Dictionary<Service, ServiceRegistrationInfo>? _ephemeralServiceInfo;
     private bool _trackerPopulationComplete;
+    private int _registrationsVersion;
 
     /// <summary>
     /// Initializes a new instance of the <see cref="DefaultRegisteredServicesTracker"/> class.
@@ -75,6 +77,9 @@ public DefaultRegisteredServicesTracker()
     /// </summary>
     public event EventHandler<IRegistrationSource>? RegistrationSourceAdded;
 
+    /// <inheritdoc/>
+    public int RegistrationsVersion => Volatile.Read(ref _registrationsVersion);
+
     /// <inheritdoc />
     public IEnumerable<IComponentRegistration> Registrations
     {
@@ -138,6 +143,8 @@ public virtual void AddRegistration(IComponentRegistration registration, bool pr
                 registration.BuildResolvePipeline(this);
             }
         }
+
+        Interlocked.Increment(ref _registrationsVersion);
     }
 
     /// <inheritdoc />
@@ -315,6 +322,7 @@ private ServiceRegistrationInfo GetInitializedServiceInfo(Service service)
         }
 
         var info = GetServiceInfo(service);
+        var instrumentationService = AutofacMetrics.Enabled ? service.ToString() : null;
         if (info.IsInitialized)
         {
             return info;
@@ -339,7 +347,13 @@ private ServiceRegistrationInfo GetInitializedServiceInfo(Service service)
         var shouldProcessCompletion = false;
         try
         {
-            Monitor.Enter(info, ref lockTaken);
+            Monitor.TryEnter(info, ref lockTaken);
+            if (!lockTaken)
+            {
+                var wait = ValueStopwatch.StartNew();
+                Monitor.Enter(info, ref lockTaken);
+                AutofacLockMetrics.RecordContention("Service", instrumentationService, wait.ElapsedTicks);
+            }
 
             if (info.IsInitialized)
             {

src/Autofac/Core/Registration/IRegisteredServicesTracker.cs

@@ -8,7 +8,7 @@ namespace Autofac.Core.Registration;
 /// <summary>
 /// Keeps track of the status of registered services.
 /// </summary>
-internal interface IRegisteredServicesTracker : IDisposable, IAsyncDisposable, IComponentRegistryServices
+internal interface IRegisteredServicesTracker : IDisposable, IAsyncDisposable, IComponentRegistryServices, IRegistrationDiagnostics
 {
     /// <summary>
     /// Fired whenever a component is registered - either explicitly or via an <see cref="IRegistrationSource"/>.

src/Autofac/Core/Registration/IRegistrationDiagnostics.cs

@@ -0,0 +1,15 @@
+// Copyright (c) Autofac Project. All rights reserved.
+// Licensed under the MIT License. See LICENSE in the project root for license information.
+
+namespace Autofac.Core.Registration;
+
+/// <summary>
+/// Provides additional diagnostic information about the component registrations without expanding the public API surface.
+/// </summary>
+internal interface IRegistrationDiagnostics
+{
+    /// <summary>
+    /// Gets the monotonically increasing version of the registrations sequence.
+    /// </summary>
+    int RegistrationsVersion { get; }
+}