Concurrent Node.js workers

workerdemo.js

import * as nodeWorker from 'worker_threads';
function sleep(ms) {
    return new Promise((resolve) => {
        setTimeout(resolve, ms);
    });
}

async function doSomething(name) {
    console.log(`${Date.now()}: Worker ${name} working ...`);
    await sleep(Math.floor(10000));
    return Math.random()
}

if (nodeWorker.isMainThread) {
    console.log("master: process id is " + process.pid);
    const threads = new Set();
    threads.add(new nodeWorker.Worker('./workerdemo.js', { workerData: { name: "Tom" } }));
    threads.add(new nodeWorker.Worker('./workerdemo.js', { workerData: { name: "Marvolo" } }));
    threads.add(new nodeWorker.Worker('./workerdemo.js', { workerData: { name: "Riddle" } }));

    for (let worker of threads) {
        worker.on('error', (err) => { throw err; });
        worker.on('exit', () => {
            threads.delete(worker);
            console.log(`master: Thread exiting, ${threads.size} still running...`);
            if (nodeWorker.size === 0) {
                console.log(primes.join('\n'));
            }
        })
        worker.on('message', (msg) => {
            console.log("master: Worker returned " + msg)
        });
    }
    for (let worker of threads) {
        worker.postMessage('go');
    }
} else {
    console.log(`worker: ${nodeWorker.workerData.name} process id is ` + process.pid);
    nodeWorker.parentPort.on('message', async (msg) => {
        const d = await doSomething(nodeWorker.workerData.name);
        nodeWorker.parentPort.postMessage(`${nodeWorker.workerData.name} computed result ${d}`);
        process.exit();
    })
}