Clooney

Clooney is an actor (ayooo) library for the web. Classes given to Clooney will be instantiated and run in a worker, keeping the main thread responsive.

⚠️ Caveat: The class cannot rely on its surrounding scope, since it is executed in an isolated context. This might change once workers support ES6 modules.

Quickstart

An example says more than 1000 words:

<script src="https://github.com/GoogleChromeLabs/clooney/raw/master/clooney.bundle.js"></script>
<script>
  (async function() {
    class MyRemoteClass {
      doExpensiveCalculation(a, b) {
        return a + b;
      }
    }

    const instance = await Clooney.spawn(MyRemoteClass);
    console.log(await instance.doExpensiveCalculation(5, 23));
  })();
</script>

I’m collecting more examples of Clooney in action in this Glitch.

Browser support

Clooney uses Comlink under the hood, and so inherits its browser compatibility matrix.

Browsers without ES6 Proxy support can use the proxy-polyfill.

Events and Functions

Functions and events are not transferable (i.e. can’t be sent from to a worker), but Clooney has special handling for them:

class MyRemoteClass {
  onClick(remoteEvent) {
    // … react to click …
  }
}

const instance = await Clooney.spawn(MyRemoteClass);
const button = document.querySelector('button');
button.addEventListener('click', instance.onClick.bind(instance));

The remoteEvent object is a mangled version of the original event to make it transferable:

const remoteEvent = {
  targetId, // = event.target.id
  targetClassList, // = [...event.target.classList]
  detail, // = event.detail
  data // = event.data
};

Promises and async methods

Clooney handles promises (and therefore, async methods) automatically:

class Actor {
  timeoutThing() {
    return new Promise(resolve => setTimeout(_ => resolve('ohai'), 1000));
  }
}

const instance = await strategy.spawn(Actor);
alert(await instance.timeoutThing()); // Will alert() after 1 second

API

Clooney’s job is to take actors (class definitions) and spawn those actors in containers (Web Workers). You can use that instance as if it was a local instance (this is magic provided by Comlink).

Clooney.spawn(class, constructorArgs)

This call is equivalent to Clooney.defaultStrategy.spawn(class, constructorArgs). Clooney creates an instance of RoundRobinStrategy as the default strategy.

Strategies

Strategies decide how many containers are spun up and where a new instance is created.

export interface Strategy {
  /**
   * `spawn` instantiates the given actor in an actor container of the strategy’s choice.
   * @returns The return type is the type as T, but every method is implicitly async.
   */
  spawn<T>(actor: new () => T, constructorArgs: any[], opts: Object): Promise<T>;
  /**
   * `terminate` calls `terminate()` on all existing containers of the strategy.
   */
  terminate(): Promise<void>;
}

Clooney.RoundRobinStrategy(opts)

RoundRobinStrategy creates up to n containers and cycles through the containers with every spawn call. RoundRobinStrategy is the default strategy.

Strategy Options

• maxNumContainers: Maximum number of containers to create (default: 1)
• newWorkerFunc: Asynchronous function that creates a new container (default: new Worker(Clooney.defaultWorkerSrc))

Clooney.asRemoteValue(obj)

asRemoteValue marks a value. If a marked value is used as an parameter or return value, it will not be transferred but instead proxied.

CDN

If you want to use Clooney from a CDN, you need to work around the same-origin restrictions that workers have:

<script src="https://cdn.jsdelivr.net/npm/clooneyjs@0.7.0/clooney.bundle.min.js"></script>
<script>
  async function newWorkerFunc() {
    const blob = await fetch(Clooney.defaultWorkerSrc).then(resp => resp.blob())
    return new Worker(URL.createObjectURL(blob));
  }

  const strategy = new Clooney.RoundRobinStrategy({newWorkerFunc});
  // Business as usual using strategy.spawn() ...
</script>

License Apache-2.0