Finally, the Common project contains the message interfaces. The build in DI system might be sufficient but I have a preference for Autofac. Autofac will be used to handle the dependency injection of complex objects. The MassTransit and MassTransit packages provide the backbone of MassTransit and the bindings to RabbitMQ. A number of packages will need to be added to the project.json " MassTransit": "3. Let’s start start building the message producer first. Returning to MassTransit we will create an example web application which sends commands and a console application which consumes messages.
#Masstransit integration tests code
Parts of the code base interested in the UserAdded event can subscribe to the messages without the add user consumer knowing about them.
Events provide a powerful mechanism for decoupling components. Consider handling the AddUser command: during the processing we might raise a number of events UserAdded, UserAddedToDatabase, UserAddedToSearchEngine, WelcomeEmailSent. Events are typically raised as a result of a command, however they need not be 1:1. Typically, they are named in the past tenseĪn event is raised in a single location but may be consumed by many services. It cannot be rejected by a handler because it is something which has already happened - you can’t change the past. It is a notificaiton that something has happened. The message bus handles the association of commands and command handlers. A command can be sent from multiple points in the code but is consumed by a single endpoint, consumer or command handler. They are named in the imperative such asĬommands can be validated and rejected by a command handler if they are invalid. Commands are instructions to perform some action. We should, perhaps, take a moment here to talk about the two types of messages we use in a message driven system. MassTransit layer an actual messaging layer on top of either RabbitMQ or Azure Service Bus which means that is provides for serialization routing. Comparing the two is beyond the scope of this article but there are some good articles on that already. For large installations I’d recommend building more tightly on top of cloud based transports, but that’s a topic for another blog post. In my mind the cost of NServiceBus is well worth it for small and medium installations.
There is, of course, a cost to running NServiceBus as it is a commercial product. NServiceBus is perhaps the most well know option. NET space which can be layered on top of raw queues. There are a couple of good options in the. Wiring would be very painful on a large scale. Nobody wants to do that for any sort of sizable application. We had to do our own wiring and even our own serialization. We did it directly with RabbitMQ which was a bit of a pain. In the last post, we created an application which can send tasks to a background processor.
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