Publishing Messages Edit on GitHub

FubuMVC's service bus is all about distributed messaging and it supports a couple different messaging patterns.

Publish and Subscribe

FubuMVC supports the concept of "publish/subscribe" publishing that allows you to decouple the message sender from the downstream recipients. FubuMVC's service bus does this by finding all the channels that are configured to receive the message type by a combination of the static routing rules and dynamic subscriptions.

To send a message, simply call IServiceBus.Send() as shown below:

public void SendPing(IServiceBus bus)
{
    bus.Send(new PingMessage());
}

Publish and Wait for an Acknowledgement

To send a message and also know when the message has been successfully received and processed by the downstream receiver, use the IServiceBus.SendAndAwait() method:

public Task SendPingWithAck(IServiceBus bus)
{
    return bus.SendAndWait(new PingMessage());
}

Sending to a Specific Destination

If you want to publish a message to a specific destination regardless of the routing rules, you can specify the Uri in the overload of IServiceBus.Send() shown below:

public void SendDirectly(IServiceBus bus)
{
    bus.Send(new Uri("lq.tcp://localhost:2245/pings"), new PingMessage());
}

Request and Reply

FubuMVC supports the request/reply messaging pattern. In this usage, you can send a message with the expectation of receiving a response from the downstream receiver.

First, the receiving handler will need to return a cascaded message for the response time. Revisiting the ping pong sample once again, a request/reply handler would look like this handler that accepts a PingMessage and sends back a PongMessage:

public class PingHandler
{
    public PongMessage Consume(PingMessage ping)
    {
        return new PongMessage();
    }
}

On the sending side, you would use the IServiceBus.Request<TResponse>(TRequest) method:

public async Task RequestReply(IServiceBus bus)
{
    var pong = await bus.Request<PongMessage>(new PingMessage());
}

Behind the scenes, FubuMVC uses envelope header values telling the receiver what response to send back and the reply Uri of the original sender to send back the response. There's nothing else users need to do to opt into the request/reply pattern.

Using Envelope sender

Lastly, if you need to take complete control over how a message is sent and use options that aren't exposed in the IServiceBus facade, you can directly use the IEnvelopeSender service directly and configure the envelope wrapper yourself as shown in this example:

public void UsingEnvelopeSender(IEnvelopeSender sender)
{
    var envelope = new Envelope
    {
        Message = new PingMessage(),
        Destination = new Uri("lq.tcp://localhost:2300/pings"),
        ContentType = "text/xml"
    };

    sender.Send(envelope);
}