Worker thread pool - Manage worker threads pool in NodeJS

workerPool.js

// workerPool.js
// Worker Thread pool

const {Worker, parentPort, MessageChannel} = require('worker_threads')

class WorkerPool {
	constructor(size, worker) {
		this.size = size
		this.worker = worker
		this.pool = []
	}

	getWorker() {
		if (this.size > this.pool.length) {
			const worker = new Worker(this.worker)
			this.pool.push(worker)
			return worker
		} else {
			return this.pool[Math.floor(Math.random() * this.size)]
		}
	}

	execute(...data) {
		return new Promise((resolve, reject) => {
			const worker = this.getWorker()
			const { port1, port2 } = new MessageChannel()

			worker.postMessage({ data, port: port1 }, [port1])

			port2.on('message', (result) => {
				resolve(result)
			})

			port2.on('error', (err) => {
				reject(err)
			})

			port2.on('close', (code) => {
				this.pool = this.pool.filter(p => p !== worker)
				worker.terminate()
			})
		})
	}
}


const pool = new WorkerPool(4, './worker.js')

const arr = [[1, 10],[2, 15],[3, 21],[4, 25],[5, 86]]

for (const ele of arr) {
	pool.execute(ele[0], ele[1])
		.then((res) => console.log(res))
}


// worker.js

const { parentPort } = require('worker_threads')

function sum(a, b) {
	return `The sum of ${a} and ${b} is ${a+b}`
}

parentPort.on('message', ({data, port}) => {
	const result = sum(...data)
	port.postMessage(result)
	port.close()
})