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Intro

At the highest level of its design, Concurrent.js is a module loader like require and import, but instead of loading a module into the main thread, it loads the module into a worker. It injects the concurrent behavior into the imported classes and functions so they can be used as usual. Concurrent.js works on Node.js, Deno, and web browsers.

Important notes

  • This is a helper library not a new implementation of Web Workers.
  • This is an early version of the library and must not be used in a real project.

Features

  • Supporting Node.js
  • Supporting browser
  • Supporting Deno
  • Executing JavaScript (ECMAScript & CommonJS)
  • Executing TypeScript
  • Executing WebAssembly
  • Accessing exported functions
  • Accessing exported classes
    • Instantiation
    • Instance members
      • Fields
      • Getters and setters
      • Methods
    • Static members
      • Fields
      • Getters and setters
      • Methods
  • Parallel execution
  • Reactive concurrency
    • Inter-worker communication
    • Event sourcing
    • Data sharing
  • Dependency injection
  • Sandboxing
  • Language interoperability (Server-side)
    • C
    • Rust
    • Python

Technical facts

  • Built upon web workers (a.k.a. worker threads).
  • Creates a worker once and reuses it.
  • Automatically cleans up a worker’s memory.
  • Automatically creates and terminates workers.
  • Has no runtime dependency.
  • Written in TypeScript with the strictest ESNext config.
  • Strictly designed to support strongly-typed programming.
  • Packaged as platform-specific bundles that target ES2020.

Hello World!

Save and run the hello world script to see it in action:

bash hello_world.sh

Usage

// load a module into a worker
const { SampleObject, sampleFunction } = await concurrent.module('sample-module').load()

// access a function
const result = await sampleFunction(/*...args*/) // call the function

// access a class
const obj = await new SampleObject(/*...args*/) // instantiate
const value = await obj.sampleProp // get a field or getter
await ((obj.sampleProp = 1), obj.sampleProp) // set a field or setter
const result = await obj.sampleMethod(/*...args*/) // call a method

// access static members of a class
const value = await SampleObject.sampleStaticProp // get a static field or getter
await ((SampleObject.sampleStaticProp = 1), SampleObject.sampleStaticProp) // set a static field or setter
const result = await SampleObject.sampleStaticMethod(/*...args*/) // call a static method

// terminate Concurrent.js
await concurrent.terminate()

Sample

Node.js (ECMAScript)

npm i @bitair/concurrent.js@latest

index.js

import { concurrent } from '@bitair/concurrent.js'
const { factorial } = await concurrent.module('extra-bigint').load()
const result = await factorial(50n)
console.log(result)
await concurrent.terminate()

package.json

{
  "type": "module",
  "dependencies": {
    "@bitair/concurrent.js": "^0.5.13",
    "extra-bigint": "^1.1.10"
  }
}
node .

Deno

index.ts

import { concurrent } from 'https://deno.land/x/concurrentjs@v0.5.13/mod.ts'
const { factorial } = await concurrent.module(new URL('services/index.ts', import.meta.url)).load()
const result = await factorial(50n)
console.log(result)
await concurrent.terminate()

services/index.ts

export { factorial } from 'extra-bigint'

deno.json

{
  "imports": {
    "extra-bigint": "npm:extra-bigint@^1.1.10"
  }
}
deno run --allow-read --allow-net index.ts

Browser

.
├── src
    ├── services
        ├── index.js
    ├── app.js
    ├── worker_script.js
    .
├── static
    ├── index.html
.

app.js

import { concurrent } from '@bitair/concurrent.js'
const { factorial } = await concurrent.module(new URL('services/index.js', import.meta.url)).load()
const result = await factorial(50n)
console.log(result)
await concurrent.terminate()

services/index.js

export { factorial } from 'extra-bigint'

worker_script.js

import '@bitair/concurrent.js/worker_script'

index.html

<!DOCTYPE html>
<html>
  <body>
    <script type="module" src="scripts/main.js"></script>
  </body>
</html>

build.sh

#!/bin/bash
npx esbuild src/app.js --bundle --format=esm --platform=browser --target=esnext --outfile=static/scripts/main.js
npx esbuild src/worker_script.js --bundle --format=esm --platform=browser --target=esnext --outfile=static/scripts/worker_script.js
npx esbuild src/services/index.js --bundle --format=esm --platform=browser --target=esnext --outfile=static/scripts/services/index.js

package.json

{
  "type": "module",
  "dependencies": {
    "@bitair/concurrent.js": "^0.5.13",
    "http-server": "^14.1.1",
    "extra-bigint": "^1.1.10"
  },
  "devDependencies": {
    "esbuild": "^0.17.8"
  }
}
bash ./build.sh && npx http-server static

Base URL

Concurrent.js uses the import.meta.url property as the base URL to resolve the scripts. It’s also possible to provide a custom base URL:

npx esbuild src/app.js --target=es6 --define:process.env.BASE_URL=\"http://127.0.0.1:8080/scripts/\" --bundle --format=esm --platform=browser --outfile=static/scripts/main.js

Parallelism

import { concurrent } from '@bitair/concurrent.js'

const extraBigint = concurrent.module('extra-bigint')

concurrent.config({ maxThreads: 16 }) // Instead of a hardcoded value use os.availableParallelism() in Node.js v19.4.0 or later

const ops = []
for (let i = 0; i <= 100; i++) {
  const { factorial } = await extraBigint.load()
  ops.push(factorial(i))
}

const results = await Promise.all(ops)
// ...rest of the code

await concurrent.terminate()

API

concurrent.load<T>(src: string | URL) : T

Loads the specified module into a worker.

  • src: string

    The path or URL of the loading module. The value of this parameter must be either an absolute path/URL or a package name.

concurrent.config(settings: ConcurrencySettings): void

Configs the global settings of Concurrent.js

  • settings: ConcurrencySettings

    • settings.disabled: boolean [default=false]

      Setting it would disable Concurrent.js without the requirement to change any other code.

    • settings.maxThreads: number [default=1]

      The max number of available threads to be spawned.

    • settings.threadIdleTimeout: number | typeof Infinity [default=Infinity]

      Number of minutes that Concurrent.js would be waiting before terminating an idle thread.

    • settings.minThreads: number [default=0]

      The number of threads that must be created when Concurrent.js starts and also kept from being terminated when are idle.

concurrent.terminate(force?: boolean): Promise<void>

Terminates Concurrent.js

  • force?: boolean [Not implemented]

    Forces Concurrent.js to exit immediately without waiting for workers to finish their tasks.

License

MIT License