NodeJS clustering with message passing from master to workers

server.js

const cluster = require('cluster');
const numCPUs = require('os').cpus().length;
const express = require('express')

const app = express();
const port = 3000;

app.get('/', (req, res) => res.send('Hello World!'));

if (cluster.isMaster) {
  console.log(`Master ${process.pid} is running`);

  // Fork workers.
  for (let i = 0; i < numCPUs; i++) {
    const worker = cluster.fork();
    worker.send('hey there');
  }

  cluster.on('exit', (worker, code, signal) => {
    console.log(`worker ${worker.process.pid} died`);
  });
} else {
  process.on('message', (message) => {
    console.log(`Worker ${process.pid} received a message from master: ${message}`);
  });
  
  app.listen(port, () => {
    console.log(`Example app listening on port ${port}!`)
  });

  console.log(`Worker ${process.pid} started`);
}