andywer/threads.js - Githubissues

Offload CPU-intensive tasks to worker threads in node.js, web browsers and electron using one uniform API.

Uses web workers in the browser, worker_threads in node 12+ and tiny-worker in node 8 to 11.

Features

First-class support for async functions & observables
Write code once, run it on all platforms
Manage bulk task executions with thread pools
Use require() and import/export in workers
Works great with webpack

Version 0.x

You can find the old version 0.12 of threads.js on the v0 branch. All the content on this page refers to version 1.0 which is a rewrite of the library with a whole new API.

Installation

npm install threads tiny-worker

You only need to install the tiny-worker package to support node.js < 12. It's an optional dependency and used as a fallback if worker_threads are not available.

Platform support

Run on node.js

Running code using threads.js in node works out of the box. Note that we wrap the native `Worker`, so `new Worker("./foo/bar")` will resolve the path relative to the module that calls it, not relative to the current working directory. That aligns it with the behavior when bundling the code with webpack or parcel.

Webpack build setup

#### Webpack config Use with the [`threads-plugin`](https://github.com/andywer/threads-plugin). It will transparently detect all `new Worker("./unbundled-path")` expressions, bundles the worker code and replaces the `new Worker(...)` path with the worker bundle path, so you don't need to explicitly use the `worker-loader` or define extra entry points. ```sh npm install -D threads-plugin ``` Then add it to your `webpack.config.js`: ```diff + const ThreadsPlugin = require('threads-plugin'); module.exports = { // ... plugins: [ + new ThreadsPlugin() ] // ... } ``` #### Node.js bundles If you are using webpack to create a bundle that will be run in node (webpack config `target: "node"`), you also need to specify that the `tiny-worker` package used for node < 12 should not be bundled: ```diff module.exports = { // ... + externals: { + "tiny-worker": "tiny-worker" + } // ... } ``` Make sure that `tiny-worker` is listed in your `package.json` `dependencies` in that case. #### When using TypeScript Note: You'll need to be using Typescript version 4+, as the types generated by threads.js are not supported in Typescript 3. Make sure the TypeScript compiler keeps the `import` / `export` statements intact, so webpack resolves them. Otherwise the `threads-plugin` won't be able to do its job. ```diff module.exports = { // ... module: { rules: [ { test: /\.ts$/, loader: "ts-loader", + options: { + compilerOptions: { + module: "esnext" + } + } } ] }, // ... } ```

Parcel bundler setup

You need to import `threads/register` once at the beginning of your application code (in the master code, not in the workers): ```diff import { spawn } from "threads" + import "threads/register" // ... const work = await spawn(new Worker("./worker")) ``` This registers the library's `Worker` implementation for your platform as the global `Worker`. This is necessary, since you cannot `import { Worker } from "threads"` or Parcel won't recognize `new Worker()` as a web worker anymore. Be aware that this might affect any code that tries to instantiate a normal web worker `Worker` and now instead instantiates a threads.js `Worker`. The threads.js `Worker` is just a web worker with some sugar on top, but that sugar might have unexpected side effects on third-party libraries. Everything else should work out of the box.

Getting Started

Basics

// master.js
import { spawn, Thread, Worker } from "threads"

const auth = await spawn(new Worker("./workers/auth"))
const hashed = await auth.hashPassword("Super secret password", "1234")

console.log("Hashed password:", hashed)

await Thread.terminate(auth)

// workers/auth.js
import sha256 from "js-sha256"
import { expose } from "threads/worker"

expose({
  hashPassword(password, salt) {
    return sha256(password + salt)
  }
})

spawn()

The hashPassword() function of the auth object in the master code proxies the call to the hashPassword() function in the worker:

If the worker's function returns a promise or an observable then you can just use the return value as such in the master code. If the function returns a primitive value, expect the master function to return a promise resolving to that value.

expose()

Use expose() to make a function or an object containing methods callable from the master thread.

In case of exposing an object, spawn() will asynchronously return an object exposing all the object's functions. If you expose() a function, spawn will also return a callable function, not an object.

Usage

Find the full documentation on the website:

Webpack

Threads.js works with webpack. Usually all you need to do is adding the threads-plugin.

See Build with webpack on the website for details.

Debug

We are using the debug package to provide opt-in debug logging. All the package's debug messages have a scope starting with threads:, with different sub-scopes:

threads:master:messages
threads:master:spawn
threads:master:thread-utils
threads:pool:${poolName || poolID}

Set it to DEBUG=threads:* to enable all the library's debug logging. To run its tests with full debug logging, for instance:

DEBUG=threads:* npm test

License

MIT