Using the event bus

The event bus does not appear in the topology drawings because it is available anywhere inside of Salt, just by importing the salt.event library. It also has the ability to call out to other module types, using the reactor system. Reactors have access to execution, state, and runner modules.

Tip

You may be wondering why we didn't cover reactor modules in this book. In truth, there is no such thing as a reactor module. Reactors are written using standard SLS files, which can include extra functionality using the renderer system. For more thorough discussions on writing and using reactors, be sure to check out Mastering SaltStack, Joseph Hall, Packt Publishing.

Because the event bus is so ubiquitous, it can be a very powerful tool for tying together the other module types into a cohesive workflow.

For example, let's take a look at Salt Cloud. It can be operated independently from the rest of Salt, but when using a Master + Minions setup, it will fire events to the...