15.2. Communicating with a worker role

Worker roles can receive the messages they need to process in either a push or a pull way. Pushing a message to the worker instance is an active approach, where you’re directly giving it work to do. The alternative is to have the role instances call out to some shared source to gather work to do, in a sense pulling in the messages they need. When pulling messages in, remember that there will possibly be several instances pulling in work. You’ll need a mechanism similar to what the Azure Queue service provides to avoid conflicts between the different worker role instances that are trying to process the same work.

Keep in mind the difference between roles and role instances, which we covered earlier. Although it’s sometimes convenient to think of workers as a single entity, they don’t run as a role when they’re running, but as one or more instances of that role. When you’re designing and developing your worker roles, keep this duality in mind. Think of the role as a unit of deployment and management, and the role instance as the unit of work assignment. This will help reduce the number of problems in your architecture.