Creating a persistence FSM model

FSM stands for finite-state machine. Akka provides the functionality to easily create an FSM within an actor. To learn more about FSM and Akka, take a look at the Finite-state machine recipe in Chapter 10, Understanding Various Akka Patterns. From this point, we will assume you have some basic knowledge of Akka FSM. Akka persistence also you to make your FSM persistent. When our FSM changes from one state to another, the change gets persisted, and therefore it's possible to restart our FSM with the latest state.

In this recipe, we will look at how to integrate persistence in your Akka FSM application using a countdown latch as an example. A countdown latch is a synchronization primitive that allows one or more threads to wait until a certain number of operations are completed on other threads. In this example, we will persist the number of operations to be able to restore in case of failure.

Getting ready

To step through this recipe, we need to import the hello...