Worker pools

Spread calls across several native Workers with one option, and control when they are created and released.

One option

One Worker runs one task at a time. Set maxWorkers and the same object spreads the calls across several native Workers.

main.ts

import { createWorker } from 'easy-web-worker/createWorker';
import workerUrl from '../getting-started/math.worker?worker&url';
import type { MathWorker } from '../getting-started/math.worker';

const math = createWorker<MathWorker>(workerUrl, {
  maxWorkers: 4,
  workerOptions: { type: 'module' },
});

export function computeAll() {
  // three calls, three threads, at the same time
  return Promise.all([math.fibonacci(40), math.fibonacci(41), math.fibonacci(42)]);
}

The calling code does not change. It does not know whether one Worker or four are behind it.

When Workers are created

With maxWorkers above 1, Workers are created as concurrent calls arrive, so an idle application pays for none of them. Two options change that:

pools.ts

import { createWorker } from 'easy-web-worker/createWorker';
import workerUrl from '../getting-started/math.worker?worker&url';
import type { MathWorker } from '../getting-started/math.worker';

// create the whole pool up front, for the fastest first call
export const warm = () =>
  createWorker<MathWorker>(workerUrl, {
    maxWorkers: 4,
    warmUpWorkers: true,
    workerOptions: { type: 'module' },
  });

// terminate idle Workers after five seconds without work
export const frugal = () =>
  createWorker<MathWorker>(workerUrl, {
    maxWorkers: 4,
    keepAlive: false,
    terminationDelay: 5_000,
    workerOptions: { type: 'module' },
  });

Option	Default	Purpose
`maxWorkers`	`1`	Maximum number of native Workers
`warmUpWorkers`	`true` for one Worker	Creates the pool during initialization
`keepAlive`	Same as `warmUpWorkers`	Keeps idle Workers alive
`terminationDelay`	`1000` ms	Wait before terminating idle Workers

A single Worker is created up front and kept alive. A pool is created on demand and released when idle, unless you ask otherwise.

Worker pools

One option

When Workers are created

What a pool is good for

Bring your own pool

Try it