interthread

"The basic idea behind an actor is to spawn a self-contained task that performs some job independently of other parts of the program. Typically these actors communicate with the rest of the program through the use of message passing channels. Since each actor runs independently, programs designed using them are naturally parallel."

• Alice Ryhl

For a comprehensive understanding of the underlying concepts and implementation details of the Actor Model,
it's recommended to read the article Actors with Tokio by Alice Ryhl ( also known as Darksonn ). This article not only inspired the development of the interthread crate but also serves as foundation for the Actor Model implementation logic in it.

What is the problem ?

To achieve parallel execution of individual objects within the same program, it is challenging due to the need for various types that are capable of working across threads. The main difficulty lies in the fact that as you introduce thread-related types, you can quickly lose sight of the main program idea as the focus shifts to managing thread-related concerns. It involves using constructs like threads, locks, channels, and other synchronization primitives. These additional types and mechanisms introduce complexity and can obscure the core logic of the program.

Moreover, existing libraries like actix, axiom, designed to simplify working within the Actor Model, often employ specific concepts, vocabulary, traits and types that may be unfamiliar to users who are less experienced with asynchronous programming and futures.

Solution

The actor macro - when applied to the implementation block of a given "MyActor" object, generates additional types and functions that enable communication between threads.

A notable outcome of applying this macro is the creation of the MyActorLive struct ("ActorName" + "Live"), which acts as an interface/handle to the MyActor object. MyActorLive retains the exact same public method signatures as MyActor, allowing users to interact with the actor as if they were directly working with the original object.

Examples

Filename: Cargo.toml

[dependencies]
interthread = "1.0.2"
oneshot     = "0.1.5" 

Filename: main.rs

pub struct MyActor {
    value: i8,
}

#[interthread::actor(channel=2)] // <-  this is it 
impl MyActor {

    pub fn new( v: i8 ) -> Self {
       Self { value: v } 
    }
    pub fn increment(&mut self) {
        self.value += 1;
    }
    pub fn add_number(&mut self, num: i8) -> i8 {
        self.value += num;
        self.value
    }
    pub fn get_value(&self) -> i8 {
        self.value
    }
}

// uncomment to see the generated code
//#[interthread::example(path="src/main.rs")] 
fn main() {

    let actor = MyActorLive::new(5);

    let mut actor_a = actor.clone();
    let mut actor_b = actor.clone();

    let handle_a = std::thread::spawn( move || { 
    actor_a.increment();
    });

    let handle_b = std::thread::spawn( move || {
    actor_b.add_number(5)
    });

    let _  = handle_a.join();
    let hb = handle_b.join().unwrap();

    // we never know which thread will
    // be first to call the actor so
    // hb = 10 or 11
    assert!(hb >= 10);

    assert_eq!(actor.get_value(), 11);
}

An essential point to highlight is that when invoking MyActorLive::new, not only does it return an instance of MyActorLive, but it also spawns a new thread that contains an instance of MyActor in it. This introduces parallelism to the program.

The code generated by actor takes care of the underlying message routing and synchronization, allowing developers to rapidly prototype their application's core functionality. This fast sketching capability is particularly useful when exploring different design options, experimenting with concurrency models, or implementing proof-of-concept systems. Not to mention, the cases where the importance of the program lies in the result of its work rather than its execution.

The same example can be run in tokio, async-std, and smol, with the only difference being that the methods will be marked as async and need to be awaited for asynchronous execution.

Examples

Filename: Cargo.toml

[dependencies]
interthread = "1.0.2"
tokio = { version="1.28.2",features=["full"]}

Filename: main.rs

pub struct MyActor {
    value: i8,
}

#[interthread::actor(channel=2,lib="tokio")] // <-  one line )
impl MyActor {

    pub fn new( v: i8 ) -> Self {
       Self { value: v } 
    }
    // if the "lib" is defined
    // object methods can be "async" 
    pub async fn increment(&mut self) {
        self.value += 1;
    }
    pub fn add_number(&mut self, num: i8) -> i8 {
        self.value += num;
        self.value
    }
    pub fn get_value(&self) -> i8 {
        self.value
    }
}

#[tokio::main]
async fn main() {

    let actor = MyActorLive::new(5);

    let mut actor_a = actor.clone();
    let mut actor_b = actor.clone();

    let handle_a = tokio::spawn( async move { 
    actor_a.increment().await;
    });

    let handle_b = tokio::spawn( async move {
    actor_b.add_number(5).await
    });

    let _  = handle_a.await;
    let hb = handle_b.await.unwrap();

    // hb = 10 or 11
    assert!(hb >= 10);

    assert_eq!(actor.get_value().await, 11);
}

The actor macro is applied to an impl block, allowing it to be used with both structs and enums to create actor implementations.

Examples

Filename: Cargo.toml

[dependencies]
interthread = "1.0.2"
oneshot     = "0.1.5" 

Filename: main.rs

#[derive(Debug)]
pub struct Dog(String);

impl Dog {
    fn say(&self) -> String {
        format!("{} says: Woof!", self.0)
    }
}

#[derive(Debug)]
pub struct Cat(String);

impl Cat {
    fn say(&self) -> String {
        format!("{} says: Meow!", self.0)
    }
}

#[derive(Debug)]
pub enum Pet {
    Dog(Dog),
    Cat(Cat),
}


#[interthread::actor(channel=2)]
impl Pet {
    // not in this case, but if 
    // the types used with `Pet` have different
    // parameters for the `new` method, 
    // simply pass a ready `Self` type
    // like this
    pub fn new( pet: Self) -> Self {
        pet
    }

    pub fn speak(&self) -> String {
        match self {
           Self::Dog(dog) => {
            format!("Dog {}",dog.say())
            },
           Self::Cat(cat) => {
            format!("Cat {}", cat.say())
            },
        }
    }
    pub fn swap(&mut self, pet: Self ) -> Self {
        std::mem::replace(self,pet)
    }
}


fn main() {

    let pet = PetLive::new( 
        Pet::Dog(Dog("Tango".to_string()))
    );

    let mut pet_a = pet.clone();
    let pet_b     = pet.clone();
    
    let handle_a = std::thread::spawn( move || {
        println!("Thread A - {}",pet_a.speak());
        // swap the the pet and return it  
        pet_a.swap(Pet::Cat(Cat("Kiki".to_string())))
    });

    let swapped_pet = handle_a.join().unwrap();

    let _handle_b = std::thread::spawn( move || {
        println!("Thread B - {}",pet_b.speak());
    }).join();

    //play with both pets now  
    println!("Thread MAIN - {}",pet.speak());
    println!("Thread MAIN - {}",swapped_pet.speak());

}

Outputs

Thread A - Dog Tango says: Woof!
Thread B - Cat Kiki says: Meow!
Thread MAIN - Cat Kiki says: Meow!
Thread MAIN - Dog Tango says: Woof!

The crate also includes a powerful macro called example that can expand the actor macro, ensuring that users always have the opportunity to visualize and interact with the generated code. Which makes actor 100% transparent macro .

Using actor in conjuction with example empowers users to explore more and more advanced techniques and unlock the full potential of parallel and concurrent programming, paving the way for improved performance and streamlined development processes.

Examples

Filename: Cargo.toml

[dependencies]
interthread = "1.0.2"
tokio = { version="1.28.2",features=["full"]}

Filename: main.rs

use tokio::time::{sleep,Duration};
pub struct MyActor;

#[interthread::actor(channel=2,lib="tokio")] 
impl MyActor {

    pub fn new() -> Self {Self}

    pub async fn sleep(&self, n:u8) {
        tokio::spawn(async move{
            // sleep one second
            sleep(Duration::from_secs(1)).await;
            println!("Task {} awake now!",n);
        });
    }
}

#[tokio::main]
async fn main(){

    let actor = MyActorLive::new();

    for i in 0..60 {

        let act_a = actor.clone();

        let _ = tokio::spawn(async move {
            act_a.sleep(i).await;
        });
    }
    // check how long
    // will take to sleep a minute 
    sleep(Duration::from_secs_f64(1.01)).await; 
}

Outputs (on my machine )

Task 34 awake now!
Task 23 awake now!
Task 25 awake now!
Task 24 awake now!
Task 5 awake now!
        ...
Task 59 awake now!
Task 42 awake now!
Task 57 awake now!
Task 58 awake now!
Task 55 awake now!

60 in total.

The above example demonstrates a more advanced usage of the actor macro, showcasing its flexibility and capabilities. In this example, we explore non-blocking behavior that doesn't modify the state of the object or return any type.

To modify the state we'll need to use some additional types "shared state types" or "thread-safe types".

Examples

use tokio::time::{sleep,Duration};
use std::sync::{Arc,Mutex};

pub struct MyActor(Arc<Mutex<u8>>);

#[interthread::actor(channel=2,lib="tokio")] 
impl MyActor {

    pub fn new() -> Self {Self(Arc::new(Mutex::new(0)))}

    pub async fn sleep_increment(&self) {
        // clone the value 
        let value = Arc::clone(&self.0);
        tokio::spawn(async move{
            // sleep one second 
            sleep(Duration::from_secs(1)).await;
            // increment the value
            let mut guard = value.lock().unwrap();
            *guard += 1;
        });
    }
    pub fn get_value(&self) -> u8 {
        self.0.lock().unwrap().clone()
    }
}

#[tokio::main]
async fn main(){

    let actor = MyActorLive::new();

    for _ in 0..60 {
        let act_clone = actor.clone();

        let _ = tokio::spawn(async move {
            act_clone.sleep_increment().await;
        });
    }
    // play with Duration
    // set it to `1.00` and see how many tasks will
    // increment after sleep 
    sleep(Duration::from_secs_f64(1.01)).await;
    println!("Total tasks - {}", actor.get_value().await);
}

Outputs ( on my machine )

Total tasks - 60

To return a type from the task, we will use a 'channel' from crate oneshot. Tokio offers its own version of oneshot.

Filename: Cargo.toml

[dependencies]
interthread = "1.0.2"
tokio = { version="1.28.2",features=["full"]}

Examples

use tokio::time::{sleep,Duration};
use tokio::sync::oneshot::{self,Sender};
use std::sync::{Arc,Mutex};
pub struct MyActor(Arc<Mutex<u32>>);
// we use argument `id`
#[interthread::actor(channel=2,lib="tokio",id=true)] 
impl MyActor {

    pub fn new() -> Self {Self(Arc::new(Mutex::new(0)))}

    pub async fn init_actor_increment(&self,val:usize, sender: Sender<MyActorLive>){
        
        // clone the value of Actor 
        let value = Arc::clone(&self.0);
        tokio::spawn(async move {
            // I prefer to initialize them like this,
            // since they are competing with each other
            // to obtain the unique ID.
            // but if you commentout this "sleep" 
            // statement it will work anyway
            sleep(Duration::from_millis(val as u64)).await;

            //create actor
            let actor = MyActorLive::new();

            // send actor
            let _ = sender.send(actor);

            // increment the value
            let mut guard = value.lock().unwrap();
            *guard += 1;
        });
    }
    pub fn get_value(&self) -> u32 {
        self.0.lock().unwrap().clone()
    }
}

#[tokio::main]
async fn main(){
    let mut handles = Vec::new();
    let actor = MyActorLive::new();
    
  
    for i in 0..1000 {
        let act_clone = actor.clone();

        let handle = tokio::spawn(async move {

            let (send,recv) = oneshot::channel();
            
            // we want to receive an instance of 
            // new actor 
            // we send channel sender   
            act_clone.init_actor_increment(i, send).await;

            // awaiting for new actor 
            recv.await
        });
        handles.push(handle);
    }
    
    let mut actors = Vec::new(); 
    // receiving 
    for handle in handles {
        let act = 
        handle.await
              .expect("Task Fails")
              .expect("Receiver Fails");
        
        actors.push(act);
    }

    println!("Total tasks - {}", actor.get_value().await);
    println!("actors.len() -> {}", actors.len());
    

    // actors can be sorted by
    // the time they were invoked
    actors.sort();
    assert_eq!(actors[0] < actors[1],true); 
    assert_eq!(actors[121] < actors[122],true); 
    assert_eq!(actors[998] < actors[999],true); 


    // check if they have unique Ids 
    for i in (actors.len() - 1) ..0{
        let target = actors.remove(i);
        if actors.iter().any(move |x| *x == target){
            println!("ActorModel Ids are not unique")
        }
    }
    eprintln!(" * end of program * ");
}

The id argument is particularly useful when working with multiple instances of the same type, each/some serving different threads. It allows for distinct identification and differentiation between these instances, enabling more efficient and precise control over their behavior and interactions.

The following example serves as a demonstration of the flexibility provided by the actor macro. It showcases how easy is to customize and modify various aspects of the code generation process.

Examples

Filename: Cargo.toml

[dependencies]
interthread = "1.0.2"
oneshot     = "0.1.5" 

Filename: main.rs

use std::sync::mpsc;
use interthread::actor;
 
pub struct MyActor {
    value: i8,
}

// this is initial macro 
// #[actor(channel=2,file="src/main.rs",edit(script(imp(play))))]
// will change to 
#[actor(channel=2, edit(script(imp(play))))]

impl MyActor {

    pub fn new( value: i8 ) -> Self {
        Self{value}
    }
    pub fn increment(&mut self) -> i8{
        self.value += 1;
        self.value
    }
    // it's safe to hack the macro in this way
    // while developing, along  with other
    // things will be created a new `Script` variant  
    // We'll catch it in `play` function
    pub fn play_get_counter(&self)-> Option<u32>{
        None
    }
}

// we have the code of `play` component
// using `edit` in conjuction with `file`
// Initiated By  : #[actor(channel=2,file="src/main.rs",edit(script(imp(play))))]  
impl MyActorScript {

    pub fn play( 
         receiver: mpsc::Receiver<MyActorScript>,
        mut actor: MyActor) {
        // set a custom variable 
        let mut call_counter = 0;
    
        while let Ok(msg) = receiver.recv() {
    
            // match incoming msgs
            // for `play_get_counter` variant
            match msg {
                // you don't have to remember the 
                // the name of the `Script` variant 
                // your text editor does it for you
                // so just choose the variant
                MyActorScript::PlayGetCounter { output  } =>
                { let _ = output.send(Some(call_counter));},
                
                // else as usual 
                _ => { msg.direct(&mut actor); }
            }
            call_counter += 1;
        }
        eprintln!("the end");
    }
}


fn main() {

    let my_act = MyActorLive::new(0);
    let mut act_a = my_act.clone();
    let mut act_b = my_act.clone();

    let handle_a = std::thread::spawn(move || {
        act_a.increment();
    });
    let handle_b = std::thread::spawn(move || {
        act_b.increment();
    });
    
    let _ = handle_a.join();
    let _ = handle_b.join();


    let handle_c = std::thread::spawn(move || {

        // as usual we invoke a method on `live` instance
        // which has the same name as on the Actor object
        // but 
        if let Some(counter) = my_act.play_get_counter(){

            println!("This call never riched the `Actor`, 
            it returns the value of total calls from the 
            `play` function ,call_counter = {:?}",counter);

            assert_eq!(counter, 2);
        }
    });
    let _ = handle_c.join();
}

The provided example serves as a glimpse into the capabilities of the actor macro, which significantly reduces the amount of boilerplate code required for interthread actors. While the example may not be immediately comprehensible, it demonstrates how the macro automates the generation of essential code, granting developers the freedom to modify and manipulate specific parts as needed.

For more details, read the

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