server.mjs

import express from 'express'
import cluster from 'cluster'
import { cpus } from 'os'
import process from 'process'

const workers = Math.min(Number(process.argv[2]) || 1, cpus().length)
const blockTime = Number(process.argv[3])

const app = express()
const port = 4000

app.get('/', (req, res) => {
  if (blockTime) {
    const now = new Date()
    while(new Date() - now < blockTime) {}
  }
  res.send('Hello World')
})

if (cluster.isPrimary) {
  console.log(`🚀 Listening on port ${port}`)
  console.log(`Number of cpus: ${cpus().length}`)
  console.log(`Number of workers: ${workers}`)
  if (blockTime) {
    console.log(`Block time milliseconds: ${blockTime}`)
  }
  
  console.log(`Primary ${process.pid} is running`)
  for (let i = 0; i < workers; i++) {
    cluster.fork()
  }
  cluster.on('exit', (worker, code, signal) => {
    console.log(`worker ${worker.process.pid} died`)
  })
} else {
  await new Promise((resolve) => app.listen({ port }, resolve))
  console.log(`Worker ${process.pid} started`)
}