Processing only n items at a time concurrently using Task Parallel Library

Question

This is all happening in a windows service.

I have a Queue (actually a ConcurrentQueue) holding items waiting to be processed

Answer 1

I'd also recommend using a BlockingCollection instead of directly using a ConcurrentQueue.

Here's an example:

public class QueuingRequestProcessor
{
  private BlockingCollection queue;

  public void QueuingRequestProcessor(int maxConcurrent)
  {
    this.queue = new BlockingCollection(maxConcurrent);

    Task[] consumers = new Task[maxConcurrent];

    for (int i = 0; i < maxConcurrent; i++)
    {
      consumers[i] = Task.Factory.StartNew(() =>
      {
        // Will wait when queue is empty, until CompleteAdding() is called
        foreach (var request in this.queue.GetConsumingEnumerable())
        {
          Process(request);
        }
      });
    }
  }

  public void Add(MyRequest request)
  {
    this.queue.Add(request);
  }

  public void Stop()
  {
    this.queue.CompleteAdding();
  }

  private void Process(MyRequestType request)
  {
    // Do your processing here
  }
}

Note that maxConcurrent in the constructor defines how many requests will be processed concurrently.