In Chapter 9, Advanced Asynchronous Recipes, we learned how to delegate costly tasks to multiple local processes, but even though this was an effective approach, it cannot be scaled beyond the boundaries of a single machine. In this section, we are going to see how it's possible to use a similar pattern in a distributed architecture, using remote workers located anywhere in a network.
The idea is to have a messaging pattern that allows us to spread tasks across multiple machines. These tasks might be individual chunks of work or pieces of a bigger task split using a divide and conquer technique.
If we look at the logical architecture represented in the following figure, we should be able to recognize a familiar pattern:
As we can see from the preceding diagram, the publish/subscribe pattern is not suitable for this type of application, as we absolutely don't want a task to be received by multiple workers. What we need instead is a message distribution...