go-actor

go-actor is tiny library for writing concurrent programs in Go using actor model.

Motivation

Intention of go-actor is to bring actor model closer to Go developers and to provide design pattern needed to build scalable and high performing concurrent programs.

Without re-usable design principles codebase of complex system can become hard to maintain. Codebase written using Golang can highly benefit from design principles based on actor model as goroutines and channels naturally translate to actors and mailboxes.

Advantage

• Entire codebase can be modelled with the same design principles where the actor is the universal primitive. Example: in microservice architected systems each service is an actor which reacts and sends messages to other services (actors). Services themselves could be made of multiple components (actors) which interact with other components by responding and sending messages.
• Golang’s goroutines and channels naturally translate to actors and mailboxes.
• System can be designed without the use of mutex. This can give performance gains as overlocking is not rare in complex components.
• Optimal for Golang's goroutine scheduler
• Legacy codebase can transition to actor based design because components modelled with go-actor have a simple interface which could be integrated anywhere.

Abstractions

go-actor's base abstraction layer only has three interfaces:

• actor.Actor is anything that implements Start() and Stop() methods. Actors created using actor.New(actor.Worker) function will create preferred actor implementation which will on start spawn dedicated goroutine to perform work of supplied actor.Worker.
  • actor.Worker encapsulates actor's executable logic. This is the only interface which developers need to write in order to describe behavior of actors.
• actor.Mailbox is an interface for message transport mechanisms between actors. Mailboxes are created using the actor.NewMailbox(...) function.

Examples

Dive into examples to see go-actor in action.

// This example will demonstrate how to create actors for producer-consumer use case.
// Producer will create incremented number on every 1 second interval and
// consumer will print whatever number it receives.
func main() {
	mailbox := actor.NewMailbox[int]()

	// Produce and consume workers are created with same mailbox
	// so that produce worker can send messages directly to consume worker
	pw := &produceWorker{outC: mailbox.SendC()}
	cw1 := &consumeWorker{inC: mailbox.ReceiveC(), id: 1}

	// Note: Example creates two consumers for the sake of demonstration
	// since having one or more consumers will produce the same result. 
	// Message on stdout will be written by first consumer that reads from mailbox.
	cw2 := &consumeWorker{inC: mailbox.ReceiveC(), id: 2}

	// Create actors using these workers and combine them to singe actor
	a := actor.Combine(
		mailbox,
		actor.New(pw),
		actor.New(cw1),
		actor.New(cw2),
	)

	// Finally all actors are started and stopped at once
	a.Start()
	defer a.Stop()

	select {}
}

// produceWorker will produce incremented number on 1 second interval
type produceWorker struct {
	outC chan<- int
	num  int
}

func (w *produceWorker) DoWork(c actor.Context) actor.WorkerStatus {
	select {
	case <-time.After(time.Second):
		w.num++
		w.outC <- w.num

		return actor.WorkerContinue

	case <-c.Done():
		return actor.WorkerEnd
	}
}

// consumeWorker will consume numbers received on inC channel
type consumeWorker struct {
	inC <-chan int
	id  int
}

func (w *consumeWorker) DoWork(c actor.Context) actor.WorkerStatus {
	select {
	case num := <-w.inC:
		fmt.Printf("consumed %d \t(worker %d)\n", num, w.id)

		return actor.WorkerContinue

	case <-c.Done():
		return actor.WorkerEnd
	}
}

Addons

go-actor is intended to be a tiny library with lean interfaces and basic mechanism providing core building blocks. However, developers may build on top of it and extend it's functionality with user or domain specific addon abstractions. This section lists addon abstractions for go-actor which could be used in addition to it.

• super is addon abstraction which aims to unify testing of actor's and worker's business logic.

Design decisions

Design decisions are documented here.

Contribution

All contributions are useful, whether it is a simple typo, a more complex change, or just pointing out an issue. We welcome any contribution so feel free to open PR or issue.

Continue reading here.