Crate acteur

Acteur Actor System

An actor system written in Rust that just works. Simple, robust, fast, documented.

Overall features of Acteur

Acteur uses async_std under the hood. This actor system work under the following premises:

• Simplicity: The API should be small, simple and intuitive
• Speed: The system should be fast and use all available CPU cores
• Documented: Everything must be documented with exhaustive examples

Regarding the implementation:

• Actors have an ID which type is defined by the user for each Actor type
• Messages are routed to an Actor and an ID
• Actor life-cycle is automatically handled by the framework
• Actors are automatically de/allocated depending of their usage
• Messages for the same Actor & ID are ordered. Everything else is executed concurrently.

State of the implementation

• ☑️ Actor is activated on first message
• ☑️ Actor can send messages to other actors
• ☑️ System can send messages to any actor
• ☑️ Actor self stop
• ☑️ Stop waits for all actors to consume all messages
• ☑️ System statistics
• ☑️ RPC like messages between actors
• ☑️ Services (statefull or stateless, like actors, without ID and processing messages concurrently)
• ☑️ Automatic deallocation of unused actors
• □ Actor deallocation configuration (based in RAM, Actor count or timeout)
• □ Subscribe to message
• □ Fan-out messages
• □ Allow more than 150.000 queued messages per actor (waiting for async_std to have unbounded channels: https://github.com/async-rs/async-std/issues/212)

Actors & Services

Acteur provides 2 ways of concurrency. Actors and Services.

Actors

Actors have an ID and will consume messages directed to the same Actor's ID sequentially. That means that if you have if you send 2 messages to the Actor User-32, they will be executed in order. On the other side, if you send a message to the Actor User-32 and other to the User-52 they will consume the messages concurrently.

That means, Actors instances keep the messages order for the same ID, but not between different IDs.

Services

Services, on the other side, have no ID and they have concurrency. That means that you choose how many instances of the Service there will be (Acteur provides a default). Services can or can't have an State, but if they have, they require to be Sync (aka Mutex).

In short. Services are like normal web services. You can have many instances and there is no synchronization of any type when consuming messages. Think of them as the primitive you use when you want to create something that doesn't fit the Actors model in this framework.

Use cases

Choose Actor for Entities (Users, Invoices, Players, anything which their instances are identified).

Choose Services for Business Logic, Infrastructure, Adapters, etc (Storage, DB access, HTTP services, calculations of some sort that doesn't belong to any Actor, etc)

Subscription or Pub/Sub (not yet implemented)

Sometime we don't want to direct messages to destination, but to subscribe to a type and wait. Acteur models the Pub/Sub patter with Services. Actors in Acteur can't perform subscriptions as that would require the framework to know all possible IDs of all possible Actor instances in order to direct the message to the correct one.

If you want to send messages to some Actors from a Subscription, you can create a Service that subscribes to a message and then figures out to what Actor IDs to send the message. For example, doing a query in the DB in order to get the set of IDs that need to receive some message.

Unlike sending/calling to services/actors, subscription doesn't know who needs to receive the message. That is the
reason behind requiring the Services to subscribe in runtime to any message they want to receive. In order to ensure
that services perform the subscriptions, it is a good idea to run acteur.preload_service<Service>(); for each service that should perform any subscription at the beginning of your Application start.

Simple Example

use acteur::{Actor, Receive, Assistant, Acteur};
use async_trait::async_trait;

#[derive(Debug)]
struct Employee {
    salary: u32
}

#[async_trait]
impl Actor for Employee {
    type Id = u32;

    async fn activate(_: Self::Id) -> Self {
        Employee {
            salary: 0 // Load from DB or set a default,
        }
    }
}

#[derive(Debug)]
struct SalaryChanged(u32);

#[async_trait]
impl Receive<SalaryChanged> for Employee {
    async fn handle(&mut self, message: SalaryChanged, _: &Assistant<Employee>) {
        self.salary = message.0;
    }
}

let sys = Acteur::new();

sys.send_to_actor_sync::<Employee, SalaryChanged>(42, SalaryChanged(55000));

sys.wait_until_stopped();

Structs

Acteur	Acteur is the main inteface to the actor runtime. It allows sending messages, stopping the runtime, set configurations, etc. Once contructed with the method "new" you can start sending messages. The system will automatically start any required actor and unload them when not used.
Assistant	This object is provided to the handle method in Receive and Respond traits for each message that an Actor receives.
ServiceConfiguration
System	This object is provided to the handle method in the Receive trait for each message that an Actor receives. The Actor's assistant allows to send messages and to execute some task over the system.

Enums

ServiceConcurrency

Traits

Actor	The main Trait from this crate.
Notify	This Trait allow Services to receive messages.
Receive	This Trait allow Actors to receive messages.
Respond	This Trait allow Actors to receive messages and, additionally, respond to them.
Serve	This Trait allow Services to receive messages and, additionally, respond to them.
Service	Services are id-less actors that can process messages with certain concurrency. The concurrency level can be configured during the "initialize" method with the ServiceConfiguration struct.