c# - Autofac - 解决多线程环境中的依赖关系

Question

public class MultithreadTester
{

    public void Run()
    {
        var builder = new ContainerBuilder();
        builder.RegisterType<ManualWork>().As<IWork>();
        builder.RegisterType<ColabManualWork>().As<IColabWork>();
        builder.RegisterType<RelaxAfterManualWork>().As<IRelax>();

        var container = builder.Build();

        //#1 - Simple single thread
        using (var scope = container.BeginLifetimeScope())
        {
            var work = scope.Resolve<IWork>();
            work.DoWork();
        }

        //#2 - Resolving dependecies in worker threads in scopes of these threads without passing lifetime scopes are container into implementation
        using (var scope = container.BeginLifetimeScope())
        {
            var work = scope.Resolve<IColabWork>();
            work.DoWork();
        }

        //#3 - Resolving dependecies in worker threads when original scope is already gone (simulates fast request on same service which spawns threads for request processing)
        IColabWork workForSample3;
        using (var scope = container.BeginLifetimeScope())
        {
            workForSample3 = scope.Resolve<IColabWork>();
        }
        workForSample3.DoWork();

        Console.ReadKey();

    }

    public interface IRelax
    {
        void DoRelax();
    }

    public class RelaxAfterManualWork : IRelax
    {
        public void DoRelax()
        {
            Console.WriteLine("Relaxing after hard work...");
            Thread.Sleep(1000);
            Console.WriteLine("Relax is done...");
        }
    }


    public interface IWork
    {
        void DoWork();
    }

    public class ManualWork : IWork
    {
        private readonly IRelax _relaxActivity;

        public ManualWork(IRelax relaxActivity)
        {
            _relaxActivity = relaxActivity;
        }

        public void DoWork()
        {
            Console.WriteLine("Ufff, this is so hard...");
            Thread.Sleep(5000);
            Console.WriteLine("Work is done...");
            _relaxActivity.DoRelax();
        }
    }

    public interface IColabWork
    {
        void DoWork();
    }

    public class ColabManualWork : IColabWork
    {
        public void DoWork()
        {
            Console.WriteLine("We must discuss how to share the workload...");
            Thread.Sleep(1500);

            Action action = () => 
            {
                //IT WOULD BE FINE TO HAVE RESOLVED DEPENDENCIES PER THREAD AND IN THREAD OWN LIFETIMESCOPE

                Console.WriteLine("Ufff, this is so hard but working with my buddies helps...");
                Thread.Sleep(2500);
                Console.WriteLine("Work is done...");
                var relaxActivity = new RelaxAfterManualWork();
                relaxActivity.DoRelax();
            };

            var thread1 = new Thread(() => { action(); });
            var thread2 = new Thread(() => { action(); });
            thread1.Start();
            thread2.Start();

            thread1.Join();
            thread2.Join();
        }
    }


}

在标记为 #1 的示例中，我正在解析 IWork 并运行一些操作。对于单线程环境，我了解 DI 中发生的事情、我应该如何使用 DI、lifetimescope 以及如何解决依赖关系。

但是我很难理解多线程环境下的依赖注入(inject)。我试图证明我遇到的一些问题是示例 #2、#3。在这些示例中，我会以某种方式需要解决 LifetimeScope 中的依赖关系，这些依赖关系将为 ColabManualWork 中的每个线程创建。当然，我不希望引用 Autofac 中的任何类以防止耦合。

我什至创建了一个简单的工厂，它适合从当前的 LifetimeScopes 创建嵌套的 LifetimeScopes:

public interface IIsolatedLifetimeScopeFactory<TA>
{
    void Create(Action<TA> action);
}

public class IsolatedLifetimeScopeFactory<TA> : IIsolatedLifetimeScopeFactory<TA>
{
    private readonly ILifetimeScope _scope;

    public IsolatedLifetimeScopeFactory(ILifetimeScope scope)
    {
        _scope = scope;
    }

    public void Create(Action<TA> action)
    {
        using (var subScope = _scope.BeginLifetimeScope())
        {
            var a = subScope.Resolve<TA>();
            action(a);
        }
    }
}

但我不太喜欢这个解决方案。存在三个大问题 - 1)所有逻辑必须在 lambda 函数(或等效方法)中； 2)如果父作用域再次被处置，Autoflac 将来可以重新实现处置子作用域的功能(这个功能已经存在几个月了)； 3) 如示例 #3 中所示，我可以在 ColabManualWork 中的任何功能启动之前处置父 LifetimeScope，因此我的工厂将使用已经处置的 LifetimeScope。

有人可以帮助我如何有效地解决工作线程中的问题吗？我读了一些与名为 Work with dependency injection in multi-threaded applications 的 SimpleInjector 相关的内容但我没有完全理解它，而且它与 Autofac 无关。在那篇文章里写着在多线程应用程序中，每个线程都应该有自己的对象图。这意味着您通常应该在线程开始执行时调用一次 container.GetInstance() 以获取用于处理该线程的根对象

如何在不与 Autofac 耦合的情况下解决工作线程中的依赖关系以及线程相关的生命周期？

Answer 1

要为每个线程提供自己的生命周期范围，您只需将 IsolatedLifetimeScopeFactory 注册为 SingleInstance。这将解决您的问题 2) 和 3)

[TestMethod]
public void MyTestMethod()
{
    var cb = new ContainerBuilder();
    cb.RegisterGeneric(typeof(IsolatedLifetimeScopeFactory<>))
        .SingleInstance();
    var container = cb.Build();

    using (var scope1 = container.BeginLifetimeScope("scope1"))
    using (var scope2 = scope1.BeginLifetimeScope("scope2"))
    {
        var factory = scope2.Resolve<IsolatedLifetimeScopeFactory<object>>();
        var tag = factory._scope.Tag; // made _scope public for testing purposes
        Assert.AreNotEqual("scope1", tag);
        Assert.AreNotEqual("scope2", tag);

        // This particular string "root" is probably not guaranteed behavior, but
        // being in the root scope is guaranteed for SingleInstance registrations.
        Assert.AreEqual("root", tag);
    }
}

您关注的问题 1) 可以通过使用不同的抽象来解决。例如，您可以将其添加到 IsolatedLifetimeScopeFactory

public Autofac.Features.OwnedInstances.Owned<TA> Create()
{
    return _scope.Resolve<Autofac.Features.OwnedInstances.Owned<TA>>();
}

如果您真的愿意，您可以将 Owned 隐藏在抽象之后，尽管我认为这有点矫枉过正。