Question

I have a fairly complex multi-threaded Windows service working, but I can’t figure out how to clean up correctly. Below is some [pseudo] code to show what I have. The actual code is much more complex, probably too much to copy/paste here.

Basically, I have a class Request that creates a thread to do the work. When a new request comes in the Listener, it sends it to the Processor, which creates the new Request and maintains the list of requests. If the service is stopped, I cleanup all the requests in the list. But when the Request work is done, how do I clean up that one instance of the class?

Thanks for any help!

Nelson

class Service
{
  Listener listener;
  Processor processor;

  OnStart()
  {
    processor = new Processor();
    listener = new Listener(processor);
  }

  OnStop()
  {
    listener.Dispose();
    processor.Dispose();
  }
}

class Listener
{
  Thread thread;
  bool terminate = false;

  Listener(Processor processor)
  {
    thread = new Thread(DoWork);
    thread.Start(processor);
  }

  DoWork(Processor processor)
  {
    WaitForConnection(NewConnection);
  }

 NewConnection(String data)
 {
    processor.NewRequest(data);

    if (terminate)
      return;

   WaitForConnection(NewConnection);
 }

  Dispose()
  {
    terminate = true;
    thread.Join();
  }
}

class Processor
{
  //I need to maintain this list so that when the service stops I can cleanly close down
  List<Request> requests = new List<Request>();

  NewRequest(string data)
  {
    request.Add(new Request(data));
  }

  Dispose()
  {
    //Cleanup each request
    foreach (Request request in requests)
    {
      request.Dispose();
    }
  }
}

class Request
{
  Thread thread;
  bool terminate;

  Request(string data)
  {
    while (true)
    {
      //Do some work
      Thread.Sleep(1000);

      if (doneWorking)
        break;

      if (terminate)
        return;
    }

    //We're done.  If I return this thread stops.  But how do I properly remove this Request instance from the Processor.requests list?
  }

  Dispose()
  {
    terminate = true;
    thread.Join();
  }
}

Answer 1

This is a rough sketch:

delegate void CompletedRequest(Request req);

class Processor : ITrackCompletion
{
    //I need to maintain this list so that when the service stops I can cleanly close down
    List<Request> requests = new List<Request>();

    public void NewRequest(string data)
    {
        lock(requests)
            request.Add(new Request(data), Complete);
    }

    public void Complete(Request req)
    {
        lock (requests)
            requests.Remove(req);
    }

    public void Dispose()
    {
        //Cleanup each request
        foreach (Request request in requests.ToArray())
        {
            request.Dispose();
        }
    }
}

class Request
{
    Thread thread;
    bool terminate;

    public Request(string data, CompletedRequest complete)
    {
        try
        {
            while (true)
            {
                //Do some work
                Thread.Sleep(1000);

                if (doneWorking)
                    break;

                if (terminate)
                    return;
            }
        }
        finally
        {
            //We're done.  If I return this thread stops.  But how do I properly remove this Request instance from the Processor.requests list?
            complete(this);
        }
    }

    void Dispose()
    {
        terminate = true;
        thread.Join();
    }
}