machine

introduction

machine is a go library to write state machine. The idea came to me when I watched Rob Pike's Lexical Scanning in Go. So the basic idea is that you create a State Machine and start with initial state. Every state either generates a new state or stops the system. There are no errors coming from state machine. Since an error can lead to another state.

I tried to provide a simple and powerful interfaces so one can easily extend the state machine into next level.

details

there are only 3 interfaces which help me to abstract the complexity of state machine.

type Joiner interface {
	Wait(timeout int64)
}

type Transitioner interface {
	Next(State)
	Fork(context.Context, ...State) Joiner
	Done()
}

type Machine interface {
	Run(context.Context, State) Joiner
}

And also the main type of my state machine State which is a simple function that accepts context.Context and Transitioner.

type State func(context.Context, Transitioner)

by just having these 4 things, we can easily build any state machines.

Joiner

Joiner has a single method. it should be block until either timeout passes or machine run finishes and processes all states.

Transitioner

Transitioner is a blue print of state pipeline. It provides state to go to another state.

Fork is special case which creates a brand new state machine for each states that being pass into it and joins them at the end by providing a single Joiner object.

Done is being used to tell the state machine that state has hit the end of the process.

Machine

Machine is the interface for the state machine engine. At the moment I have provided a simple local state machine. but consider this, you can extend it and make it as a distributed state machine.

Run starts the engine by providing context.Context and first initial State. context.Context is being used as a way to share context with all states inside that particular state machine and ability to cancel and stop state machine in the middle of process.

Next

• implement a distributed version of state machine using this interface
• implement more examples

Continue

The project will be continued at github.com/alinz/machine