How to get a second System.Thread.ThreadPool?

Question

If I use the ThreadPool in a nested way, my application hangs:

 ThreadPool.QueueUserWorkItem((state) =>
      ThreadPool.QueueUserWorkItem(Action));
         


        

Answer 1

One way is using BlockingCollection. This is the class i build for it:

Updated at 2018-04-23:

public class WorkerPool : IDisposable
{
    BlockingCollection queue = new BlockingCollection();
    List taskList;
    private CancellationTokenSource cancellationToken;
    int maxWorkers;
    private bool wasShutDown;

    int waitingUnits;

    public WorkerPool(CancellationTokenSource cancellationToken, int maxWorkers)
    {
        this.cancellationToken = cancellationToken;
        this.maxWorkers = maxWorkers;
        this.taskList = new List();
    }
    public void enqueue(T value)
    {
        queue.Add(value);
        waitingUnits++;
    }
    //call to signal that there are no more item
    public void CompleteAdding()
    {
        queue.CompleteAdding();          
    }

    //create workers and put then running
    public void startWorkers(Action worker)
    {
        for (int i = 0; i < maxWorkers; i++)
        {
            taskList.Add(new Task(() =>
            {
                string myname = "worker " + Guid.NewGuid().ToString();

                try
                {
                    while (!cancellationToken.IsCancellationRequested)
                    {                     
                        var value = queue.Take();
                        waitingUnits--;
                        worker(value);
                    }
                }
                catch (Exception ex) when (ex is InvalidOperationException)  //throw when collection is closed with  CompleteAdding method. No pretty way to do this.
                {
                    //do nothing
                }
            }));
        }

        foreach (var task in taskList)
        {
            task.Start();
        }
    }

    //wait for all workers to be finish their jobs
    public void await()
    {
        while (waitingUnits >0 || !queue.IsAddingCompleted)
            Thread.Sleep(100);

        shutdown();
    }

    private void shutdown()
    {
        wasShutDown = true;
        Task.WaitAll(taskList.ToArray());            
    }

    //case something bad happen dismiss all pending work
    public void Dispose()
    {
        if (!wasShutDown)
        {
            queue.CompleteAdding();
            shutdown();
        }
    }
}

To see it working build this unit test:

[TestMethod]
public void workerPoolTest()
{
    WorkerPool workerPool = new WorkerPool(new CancellationTokenSource(), 5);

    workerPool.startWorkers(value =>
    {
        log.Debug(value);
    });

    for (int i = 0; i < 100; i++)
    {
        workerPool.enqueue(i);
    }
    workerPool.CompleteAdding();
    workerPool.await();
}

Now you can have as many polls has you like, just by creating new WorkPool objects.

Note that the code is not fully tested.