c# - 强制某些代码始终在同一个线程上运行

问题描述

我们有一个旧的第 3 方系统（我们称之为 Junksoft® 95），我们通过 PowerShell 进行交互（它公开了一个 COM 对象），我正在将它包装在一个 REST API（ASP.NET Framework 4.8 和 WebAPI 2）。我使用System.Management.Automationnuget 包创建了一个PowerShell我将 Junksoft 的 COM API 实例化为dynamic然后使用的对象的对象：

//I'm omitting some exception handling and maintenance code for brevity
powerShell = System.Management.Automation.PowerShell.Create();
powerShell.AddScript("Add-Type -Path C:\Path\To\Junksoft\Scripting.dll");
powerShell.AddScript("New-Object Com.Junksoft.Scripting.ScriptingObject");
dynamic junksoftAPI = powerShell.Invoke()[0];

//Now we issue commands to junksoftAPI like this:
junksoftAPI.Login(user,pass);
int age = junksoftAPI.GetAgeByCustomerId(custId);
List<string> names = junksoftAPI.GetNames();

当我在同一个线程上运行所有这些（例如在控制台应用程序中）时，这工作正常。但是，由于某种原因，当我放入a并从我的网络应用程序中的不同控制器使用它时，这通常不起作用。我说通常是因为当 ASP.NET 碰巧将传入调用传递给在其上创建的线程时，这实际上是有效的。如果没有，Junksoft 95 会给我一个错误。junksoftAPISystem.Web.Caching.CachejunksoftAPI

我有什么办法可以确保所有交互都junksoftAPI发生在同一个线程上？

请注意，我不想将整个 Web 应用程序变成单线程应用程序！控制器和其他地方的逻辑应该在不同的线程上正常发生。它应该只是 Junksoft 特定线程上发生的 Junksoft 交互，如下所示：

[HttpGet]
public IHttpActionResult GetAge(...)
{
    //finding customer ID in database...

    ...

    int custAge = await Task.Run(() => {
        //this should happen on the Junksoft-specific thread and not the next available thread
        var cache = new System.Web.Caching.Cache();
        var junksoftAPI = cache.Get(...); //This has previously been added to cache on the Junksoft-specific thread
        return junksoftAPI.GetAgeByCustomerId(custId);
    });

    //prepare a response using custAge...
}

标签： c#asp.netmultithreadingpowershellasp.net-web-api2

解决方案

您可以创建自己的单例工作线程来实现此目的。这是您可以将其插入 Web 应用程序的代码。

public class JunkSoftRunner
{
    private static JunkSoftRunner _instance;

    //singleton pattern to restrict all the actions to be executed on a single thread only.
    public static JunkSoftRunner Instance => _instance ?? (_instance = new JunkSoftRunner());

    private readonly SemaphoreSlim _semaphore;
    private readonly AutoResetEvent _newTaskRunSignal;

    private TaskCompletionSource<object> _taskCompletionSource;
    private Func<object> _func;

    private JunkSoftRunner()
    {
        _semaphore = new SemaphoreSlim(1, 1);
        _newTaskRunSignal = new AutoResetEvent(false);
        var contextThread = new Thread(ThreadLooper)
        {
            Priority = ThreadPriority.Highest
        };
        contextThread.Start();
    }

    private void ThreadLooper()
    {
        while (true)
        {
            //wait till the next task signal is received.
            _newTaskRunSignal.WaitOne();

            //next task execution signal is received.
            try
            {
                //try execute the task and get the result
                var result = _func.Invoke();

                //task executed successfully, set the result
                _taskCompletionSource.SetResult(result);
            }
            catch (Exception ex)
            {
                //task execution threw an exception, set the exception and continue with the looper
                _taskCompletionSource.SetException(ex);
            }

        }
    }

    public async Task<TResult> Run<TResult>(Func<TResult> func, CancellationToken cancellationToken = default(CancellationToken))
    {
        //allows only one thread to run at a time.
        await _semaphore.WaitAsync(cancellationToken);

        //thread has acquired the semaphore and entered
        try
        {
            //create new task completion source to wait for func to get executed on the context thread
            _taskCompletionSource = new TaskCompletionSource<object>();

            //set the function to be executed by the context thread
            _func = () => func();

            //signal the waiting context thread that it is time to execute the task
            _newTaskRunSignal.Set();

            //wait and return the result till the task execution is finished on the context/looper thread.
            return (TResult)await _taskCompletionSource.Task;
        }
        finally
        {
            //release the semaphore to allow other threads to acquire it.
            _semaphore.Release();
        }
    }
}

用于测试的控制台主要方法：

public class Program
{
    //testing the junk soft runner
    public static void Main()
    {
        //get the singleton instance
        var softRunner = JunkSoftRunner.Instance;

        //simulate web request on different threads
        for (var i = 0; i < 10; i++)
        {
            var taskIndex = i;
            //launch a web request on a new thread.
            Task.Run(async () =>
            {
                Console.WriteLine($"Task{taskIndex} (ThreadID:'{Thread.CurrentThread.ManagedThreadId})' Launched");
                return await softRunner.Run(() =>
                {
                    Console.WriteLine($"->Task{taskIndex} Completed On '{Thread.CurrentThread.ManagedThreadId}' thread.");
                    return taskIndex;
                });
            });
        }
    }   
}

输出：

请注意，尽管该函数是从不同的线程启动的，但代码的某些部分始终始终在 ID 为“5”的同一上下文线程上执行。

但请注意，虽然所有的 Web 请求都是在独立线程上执行的，但它们最终会等待一些任务在单例工作线程上执行。这最终会在您的 Web 应用程序中造成瓶颈。无论如何，这是您的设计限制。

c# - 强制某些代码始终在同一个线程上运行

问题描述

解决方案

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