Dan McKinley

I got a chance to mess around with the Concurrency and Coordination Runtime (CCR) bits recently. Before I get into that, first check out this real-life code I wrote this week.

public static class NotificationQueue
{
    private static Queue<Notification> _queue;
    private static Semaphore _work;

    static NotificationQueue()
    {
        _queue = new Queue<Notification>();
        _work = new Semaphore(0, int.MaxValue);
    }

    public static void Enqueue(Notification n)
    {
        lock (_queue)
        {
            _queue.Enqueue(n);
        }
        _work.Release();
    }

    public static Notification Dequeue()
    {
        _work.WaitOne();
        lock (_queue)
        {
            return _queue.Dequeue();
        }
    }
}

The idea here is to post notifications to the queue from many threads, and have a single notification thread sending the messages out from something like this:

private static void NotifyThreadProc()
{
    while(!Abort())
        NotificationQueue.Dequeue().Send();
}

The documentation for CCR is pretty sparse at this point, limited to just this paper [pdf], the Channel9 video, and this Wiki. Some of the particulars seem to have changed significantly, but I was able to figure out how to replicate my explicitly-threaded notification queue:

public class NotificationService : CcrServiceBase
{
    private Port<Notification> _port;

    public NotificationService()
        : base(new DispatcherQueue("foo"))
    {
        _port = new Port<Notification>();
        Activate(Arbiter.Receive(true, _port,
        delegate(Notification n)
        {
            n.Send();
        }));
    }

    public void Post(Notification n)
    {
        _port.Post(n);
    }
}

That's pretty awesome: notice that no explicit locks or waits are necessary, and I don't need to write the NotificationThreadProc or the code required to start it. I just need to make a NotificationService and start posting to it.

I can't say it's the most immediately comprehensible API I've ever seen, but hopefully that will change with more documentation and some polish. It's also possible that I am just warped from years of using the lower-level concepts. Overall this is awfully impressive for a library.