Multiple Workers in One File

Piscina allows you to define multiple worker functions within a single file. This approach can be useful when you have related tasks that you want to keep in one module.

In the example below, for each task, pool.run() is called with two arguments:

• The task data ({ a: 2, b: 3 })
• An options object specifying the name of the function to use.

Javascript

index.js

'use strict';

const Piscina = require('piscina');
const { resolve } = require('path');

const pool = new Piscina({ filename: resolve(__dirname, 'worker.js') });

(async () => {
  console.log(await Promise.all([
    pool.run({ a: 2, b: 3 }, { name: 'add' }),
    pool.run({ a: 2, b: 3 }, { name: 'multiply' })
  ]));
})();

index.mjs

import { Piscina } from 'piscina';

const pool = new Piscina({
  filename: new URL('./worker.mjs', import.meta.url).href
});

console.log(await Promise.all([
  pool.run({ a: 2, b: 3 }, { name: 'add' }),
  pool.run({ a: 2, b: 3 }, { name: 'multiply' })
]));

Typescript

index.ts

import Piscina from 'piscina';
import { resolve } from 'path';

interface TaskInput {
  a: number;
  b: number;
}

const pool = new Piscina({ filename: resolve(__dirname, 'worker.ts') });

(async () => {
  console.log(await Promise.all([
    pool.run<number, TaskInput>({ a: 2, b: 3 }, { name: 'add' }),
    pool.run<number, TaskInput>({ a: 2, b: 3 }, { name: 'multiply' })
  ]));
})();

Here's the worker file that defines multiple functions:

Javascript

worker.js

'use strict';

function add ({ a, b }) { return a + b; }
function multiply ({ a, b }) { return a * b; };

add.add = add;
add.multiply = multiply;

// The add function is the default handler, but
// additional named handlers are exported.
module.exports = add;

worker.mjs

export function add ({ a, b }) { return a + b; }
export function multiply ({ a, b }) { return a * b; };

Typescript

worker.ts

import { resolve } from "path";

interface TaskInput {
  a: number;
  b: number;
}

function add({ a, b }: TaskInput): number { return a + b; }
function multiply({ a, b }: TaskInput): number { return a * b; }

export { add, multiply };
export const filename = resolve(__filename);

You can also check out this example on github.