OpenWebProject Workers

Multithreaded worker pool

Installation

npm install owp.workers --save

Usage

import Workers from "owp.workers";

//Create new workers instance. Ie a new worker pool.

//Pool size defaults to number of logical cores.
const workers = new Workers();

//OR manually specify pool size.
const workers = new Workers(4);

Add new work

Format

workers.add(file:string||constructor, message:any, transfer:array) => Promise

Example echo

• Runs worker in file "workerEcho.js".
  • File parameter can be the workers file name or the constructor for the worker.
  • Import constructor and then pass is used with webpack.
• Passes message "Hello World" to worker.
  • Message could be any data you want to pass not just a string.
  • Message is optional.

workers.add("workerEcho.js", "Hello World")
    .then(console.log) => "Hello world"

Example sum

• The buffer in TypedArrays like Int32Array cant be transfered to the worker thread using pass by reference instead of value, but the reference is remove from the original/calling thread.

const list = new Int32Array(3);
list[0] = 25;
list[1] = 666;
list[2] = 19;

workers.add("workerSum.js", list, [list.buffer])
    .then(console.log) => 710

Worker js format

• onmessage(event) callback is triggered when worker starts. This contains an event.data field to get message.
• Worker calls postMessage(data) to give result and terminate worker.

workerEcho.js

onmessage = (e) => {
    postMessage(e.data);
};

workerSum.js

onmessage = (e) => {
    const list = e.data;
    let sum = 0;
    for (let i = 0; i < list.length; ++i) {
        sum += list[i];
    }
    postMessage(sum);
};