How can I throttle a WCF MSMQ endpoint? - wcf

Question

I'm new to WCF and just learning how to get a client to talk to a host (both in console applications) using MSMQ.
I want to be able to send messages from client to host and have the host pick them up immediately or, if the host is stopped, to continue where it left off when it is restarted.
I've got this almost working but I find that when I restart the host with ten messages in the queue, the messages are not processed in the queue order. I assume there's some multithreading going on that makes them appear out of order. I'd like to be able to limit the WCF service to processing one message at a time to stop this happening (unless there's a better solution).
It's essential to a system that I'm about to work on that the MSMQ messages are processed in order and not in parallel.
The code for my service contract is:
[ServiceContract(Namespace = "http://www.heronfoods.com/DemoService")]
public interface IDemoService
{
[OperationContract(IsOneWay = true)]
void SendMessage(string message);
}
For the Service contract implementation I've got this. (The console output is because this is a demo app for me to learn from):
public class DemoService : IDemoService
{
public void SendMessage(string message)
{
Console.WriteLine("{0} : {1}", DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss"), message);
}
}
My host application is a console application with the following code:
class Program
{
static void Main(string[] args)
{
Console.Title = "WCF Host";
using (var host = new ServiceHost(typeof(Library.DemoService)))
{
var endpoint = new ServiceEndpoint(
ContractDescription.GetContract(typeof(Library.IDemoService)),
new NetMsmqBinding(NetMsmqSecurityMode.None),
new EndpointAddress("net.msmq://localhost/private/test"));
host.AddServiceEndpoint(endpoint);
host.Open();
Console.WriteLine("Host Active");
Console.ReadLine();
}
}
}
The client is equally simple:
class Program
{
static void Main(string[] args)
{
Console.Title = "WCF Client";
IDemoService proxy = ChannelFactory<IDemoService>.CreateChannel(
new NetMsmqBinding(NetMsmqSecurityMode.None),
new EndpointAddress("net.msmq://localhost/private/test")
);
do
{
string msg = Console.ReadLine();
if (msg=="")
break;
else
proxy.SendMessage(msg);
} while (true);
}
}

Answer 1

I am assuming your queue is not transactional.
While I'm not certain there's a way to throttle netMsmqBinding to a single thread, you shouldn't need to apply this restriction.
To guarantee ordered delivery you only need to make your queue transactional and then apply the exactlyOnce attribute to the netMsmqBinding configuration.
See example here.