Actix

Actix is a Rust actors framework.

• User Guide
• API Documentation (Development)
• API Documentation (Releases)
• Cargo package: actix
• Minimum supported Rust version: 1.39 or later

Features

• Async/Sync actors.
• Actor communication in a local/thread context.
• Uses Futures for asynchronous message handling.
• HTTP1/HTTP2 support (actix-web)
• Actor supervision.
• Typed messages (No Any type).

Usage

To use actix, add this to your Cargo.toml:

[dependencies]
actix = "0.9"

Initialize Actix

In order to use actix you first need to create a System.

fn main() {
    let system = actix::System::new("test");

    system.run();
}

Actix uses the tokio event loop. System::new() creates a new event loop and starts the System actor. system.run() starts the tokio event loop, and will finish once the System actor receives the SystemExit message.

Let's create a simple Actor.

Implement an Actor

In order to define an actor you need to define a struct and have it implement the Actor trait.

use actix::{Actor, Addr, Arbiter, Context, System};

struct MyActor;

impl Actor for MyActor {
    type Context = Context<Self>;

    fn started(&mut self, ctx: &mut Self::Context) {
       println!("I am alive!");
       System::current().stop(); // <- stop system
    }
}

fn main() {
    let system = System::new("test");

    let addr = MyActor.start();

    system.run();
}

Spawning a new actor is achieved via the start and create methods of the Actor trait. It provides several different ways of creating actors, for details check docs. You can implement started, stopping and stopped methods of the Actor trait. started gets called when actor starts and stopping when actor finishes. Check API documentation for more information on the actor lifecycle.

Handle messages

An Actor communicates with another Actor by sending messages. In actix all messages are typed. Let's define a simple Sum message with two usize parameters, and an actor which will accept this message and return the sum of those two numbers.

use futures::{future, Future};
use actix::*;

// this is our Message
struct Sum(usize, usize);

// we have to define the response type for `Sum` message
impl Message for Sum {
    type Result = usize;
}

// Actor definition
struct Summator;

impl Actor for Summator {
    type Context = Context<Self>;
}

// now we need to define `MessageHandler` for the `Sum` message.
impl Handler<Sum> for Summator {
    type Result = usize;   // <- Message response type

    fn handle(&mut self, msg: Sum, ctx: &mut Context<Self>) -> Self::Result {
        msg.0 + msg.1
    }
}

fn main() {
    let sys = System::new("test");

    let addr = Summator.start();
    let res = addr.send(Sum(10, 5));  // <- send message and get future for result

    Arbiter::spawn(res.then(|res| {
        match res {
            Ok(result) => println!("SUM: {}", result),
            _ => println!("Something wrong"),
        }

        System::current().stop();
        future::result(Ok(()))
    }));

    sys.run();
}

All communications with actors go through an Addr object. You can do_send a message without waiting for a response, or send an actor with specific message. The Message trait defines the result type for a message.

Actor state and subscription for specific messages

You may have noticed that methods of Actor and Handler traits accept &mut self, so you are welcome to store anything in an actor and mutate it whenever necessary.

Address objects require an actor type, but if we just want to send a specific message to an actor that can handle the message, we can use the Recipient interface. Let's create a new actor that uses Recipient.

use std::time::Duration;
use actix::prelude::*;

#[derive(Message)]
struct Ping { pub id: usize }

// Actor definition
struct Game {
    counter: usize,
    addr: Recipient<Ping>,
}

impl Actor for Game {
    type Context = Context<Game>;
}

// simple message handler for Ping message
impl Handler<Ping> for Game {
    type Result = ();

    fn handle(&mut self, msg: Ping, ctx: &mut Context<Self>) {
        self.counter += 1;

        if self.counter > 10 {
            System::current().stop();
        } else {
            println!("Ping received {:?}", msg.id);

            // wait 100 nanos
            ctx.run_later(Duration::new(0, 100), move |act, _| {
                act.addr.do_send(Ping{id: msg.id + 1});
            });
        }
    }
}

fn main() {
    let system = System::new("test");

    // To get a Recipient object, we need to use a different builder method
    // which will allow postponing actor creation
    let addr = Game::create(|ctx| {
        // now we can get an address of the first actor and create the second actor
        let addr = ctx.address();
        let addr2 = Game{counter: 0, addr: addr.recipient()}.start();

        // let's start pings
        addr2.do_send(Ping{id: 10});

        // now we can finally create first actor
        Game{counter: 0, addr: addr2.recipient()}
    });

    system.run();
}

chat example

There is a chat example which provides a basic example of networking client/server service.

fectl

You may consider checking out fectl utility. It is written with actix and shows how to create networking application with relatively complex interactions.

Contributing

All contributions are welcome, if you have a feature request don't hesitate to open an issue!

License

This project is licensed under either of

• Apache License, Version 2.0, (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

Code of Conduct

Contribution to the actix crate is organized under the terms of the Contributor Covenant, the maintainer of actix, @fafhrd91, promises to intervene to uphold that code of conduct.