Theta

An actor framework for Rust

Overview

Theta is an ergonomic yet minimal and performant application framework based on actor model.

• Async Actor
  • An actor instance is a very thin wrapper around a tokio::task and two MPMC channels.
  • ActorRef is just a single pointer(MPMC sender).
• Built-in remote
  • Distributed actor system powered by P2P network, iroh.
  • Even ActorRef could be passed across network boundary as regular data in message.
  • Available with feature remote.
• Built-in monitoring
  • "Monitor" suggested by Carl Hewitt's Actor Model is implemented as (possibly remote) monitoring feature.
  • Available with feature monitor.
• Built-in persistence
  • Seamless respawn of actor from snapshot on file system, AWS S3 etc.
  • Available with feature persistence.
• WASM support (WIP)
  • Compile to WebAssembly for running in browser or other WASM environments.

Example

cargo add theta

use serde::{Deserialize, Serialize};
use theta::prelude::*;

#[derive(Debug, Clone, ActorArgs)]
struct Counter {
    value: i64,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct GetValue;

#[actor("96d9901f-24fc-4d82-8eb8-023153d41074")]
impl Actor for Counter {
    type View = Nil;

    // Behaviors will generate single enum Msg for the actor
    const _: () = {
        async |amount: i64| { // Behavior can access &mut self
            self.value += amount;
        };

        async |GetValue| -> i64 {  // Behavior may or may not have return
            self.value 
        };
    };
}

#[tokio::main]
async fn main() -> anyhow::Result<()> {
    let ctx = RootContext::init_local();
    let counter = ctx.spawn(Counter { value: 0 });

    let _ = counter.tell(5); // Fire-and-forget

    let current = counter.ask(GetValue).await?; // Wait for response
    println!("Current value: {current}");       // Current value: 5

    Ok(())
}

🚧 WIP

Theta is currently under active development and API is subject to change. Not yet recommended for any serious business.

Todo

• Core
  • Make Result::Err implementing std::fmt::Display on tell to be logged as tracing::error! to prevent silent failure or code duplication
  • Use concurrent hashmap
  • Fix duplicated removing disconnected peer message
• Macros
  • Make actor macro to take identifier as ActorId
• Supervision
  • Factor out supervision as a optional feature
• Remote
  • Define lifetime behavior of exported actors (Currently, exported actor will never get dropped)
  • Deduplicate simultanious connection attempt to each other
  • Support full NodeAddr including Url format definition and sharing routing information between peers
• Persistence
  • Cover partial persistence case; some could be stored in storage, but some data should be passed in runtime
  • Have respawn API to take closure, not value.
• Actor pool
  • Actor pool (task stealing with anonymous dynamic actors and MPMC)

License

Licensed under the MIT License.