These are the goals - Rebus should have:
- a simple and intuitive configuration story
- a few well-selected options
- no doodleware
- dependency only on .NET 4 BCL
- integration with external dependencies via small and dedicated projects
- the best error messages
- a frictionless getting-up-and-running-experience
and in doing this, I want Rebus to align very well with NServiceBus, allowing users (myself included) to easily migrate to NServiceBus at some point in a project's lifetime, if Rebus for some reason falls short.
Oh, and Rebus is free as in beer and speech.
I am a happy NServiceBus user, and I still am. It just puzzles me that
- NServiceBus is 60 KLOC spread across 200+ projects - the code is hard to read
- Errors are often hard to diagnose
- Messing up during configuration yields weird errors at best, and no warnings or signs of things being wrong at worst
- NServiceBus went from being absolutely free to be licensed
I realize that NServiceBus is pretty cheap when you think of all the good things it can do for you, but to many people I think the license fee is an annoyance that will hinder them in introducing NServiceBus in all of their awesome projects - Which is a shame!
Then why don't I just use MassTransit then? Well, I wanted to do that, but I had so much trouble figuring out the philosophy of the MassTransit project that I gave up learning how to use it. I don't like how it needs a central runtime service to manage subscriptions, and I had a hard time figuring out how to make it work. And then there's the option of using PGM over MSMQ, but it just didn't work how I wanted it to work. Long story short: Too hard to get started!
Therefore, I wanted to try building a simple alternative to NServiceBus. Mainly as a personal research project, but also for myself to use in projects so I don't have to worry about licensing.
More info coming soon at http://mookid.dk/oncode/rebus
One day, maybe I'll tweet something as well... @mookid8000
Pretty clunky at the moment, I'm sorry... haven't gotten into the configuration API story yet. Right now, this is how you get going with Rebus:
First, decide how you want to
IReceiveMessages - Rebus has something that can do both:
MsmqMessageQueue - therefore:
var msmq = new MsmqMessageQueue("service_input_queue");
Then, decide how subscriptions and sagas are to be stored - let's be serious about this:
var connectionString = "data source=.;initial catalog=rebus_subscriptions;integrated security=sspi"; var subscriptionStorage = new SqlServerSubscriptionStorage(connectionString, "subscriptions"); var sagaPersister = new SqlServerSagaPersister(connectionString, "saga_index", "sagas");
Now, figure out how to go from
TMessage to instances of something that implements
IHandleMessages<TMessage>. This is where you'd probably insert your favorite IoC container. Let's pretend that I implemented
IActivateHandlers in a
CastleWindsorHandlerActivator (it's only two methods) - that would allow me to do this:
var container = GetWindsorContainerFromSomewhere(); var handlerActivator = new CastleWindsorHandlerActivator(container);
Now, figure out how a given message type should be mapped to the name of the endpoint that owns that message type - you do that by implementing
IDetermineDestination (it's one single method that maps from
string) - if I'm OK with specifying it with the NServiceBus syntax (i.e. the
<UnicastBusConfig> element from an NServiceBus app.config), I can use
var endpointMapper = new DetermineDestinationFromNServiceBusEndpointMappings();
Now, figure out how to
ISerializeMessages - at the moment there's
var serializer = new JsonMessageSerializer();
Lastly, think about whether some types of handlers should be invoked first as each handler pipeline gets executed... if that is not the case, just use
var inspector = new TrivialPipelineInspector();
and NOW we're ready to create the bus:
var bus = new RebusBus(handlerActivator, msmq, msmq, subscriptionStorage, sagaPersister, endpointMapper, serializer, inspector);
That created it. Let's make the bus start receiving messages:
If you've used NServiceBus, lots of things will immediately make sense with Rebus - everything about sending, publishing, subscribing, etc is the same. That also means that you can use all of your awesome NServiceBus skills with Rebus.
Well, that was a teaser. More stuff coming up some time in the future. I know that
RebusBus has a pretty big constructor, but that's by design ;)
Rebus is licensed under Apache License, Version 2.0. Basically, this license grants you the right to use Rebus however you see fit.