Getting started with NServiceBus

In this post I am going to give a quick introduction into NServiceBus and how this can change the way you think or design distributed application for an enterprise.

Before we get into specifics of NServiceBus lets see what is an Enterprise Service bus and how does it fits into the realm of an enterprise. So the Wikipedia definition is

   An enterprise service bus (ESB) is a software architecture model used for designing and    implementing the interaction and communication between mutually interacting software    applications in Service Oriented Architecture. As a software architecture model for    distributed computing it is a specialty variant of the more general client-server software    architecture model and promotes strictly asynchronous message oriented design for    communication and interaction between applications. Its primary use is in Enterprise    Application Integration of heterogeneous and complex landscapes.

So here are some of the key features of NServiceBus :-

• It’s not a centralized broker like BizTalk or IBM Websphere Message Broker
• It’s not a Service Communication Framework like WCF.
• Build on top of MSMQ.
• Focuses on messaging and publish/subscribe model.
• It’s very robust and reliable
• There is no synchronous communication
• The Community Edition of NServiceBus is absolutely free and can handle up to 30 messages/sec which comes out to be around 2.59 million message a day on a decent quad-core server machine.
• The licensed version of NService is merely $2000 per license and can handle 100 messages/sec or 86.4 million messages.
• Highly extensible
• Written by the software simplest the great Udi Dahan.

Okay that’s was like the product overview but if you are like me, you might be itching to go ahead and use this stuff. So here is how you can jump into the NServiceBus wagon (oops the pun ).

• Go to http://nservicebus.com
• Click on “Download v2.5 SP1″
• Unzip the file and run RunMeFirst.bat as an admin
• Install or configure MSMQ
• Go to the samples folder and open the Full Duplex project

Just to get a feel of what the project structure looks so here it.

As you can see the project structure is self-explanatory, there is a client and a server and client is going to send a message and the server will take process the message and return it back to client.Lets run the project and see what happens.

and as you can see in the above figure that client and server are launched and ready to exchange messages. Lets hit enter in the Client console window and you will see the message gets send to the server with a Guid, which is received by the server and server sends back the message back to the client.

So till now nothing special but it’s time to go deeper and start tinkering with NServiceBus to understand some more. What I’ll now do is from the solution this time I’ll run only the client and not the server to mimic “a real life distributed application with reliable messaging” kind of scenario. So lets run the client project in isolation.

and we see that the client console windows gets launched and let hit enter to send a message to the service.So this is how it looks when we do that.

Now we will look how this message gets routed by NServiceBus. Lets open MSMQ and see where this message is routed and stored in MSMQ.

If you remember from the client console window that a message with a guid 3e8eeb98-0130-429a-862c-a56f5a02d95b but the message id in the server queue is something different and you must be wondering about this mismatch.

Lets open the message and see what’s in there.

So here in the message you can see the Data Id which matches the guid and this is how the server can correlated the incoming messaging and outgoing message to the client.

Now lets run the solution again and see how the NServiceBus will pick up the message process it and send it back to client and client will display the returned message from the server.

Viola !!! We see the NServiceBus picks up the message and processes it and return the message back to client and the client receives the processed message.If at this point you open the MSMQ and you will see that the message has been processed from the Server Queue and since the client has received the message the message disappears from the client queue. This is a good project to understand the core of NServiceBus and getting started with it.

One of thing I like about NServiceBus is the documentation is superb and all the sample projects are really good to understand. Hopefully I will able to bring more real-life & complex implementation of NServiceBus as I go my implementing in my current project.Till then …..

Enjoy !!!