Cluster 集群

const cluster = require('cluster')
const http = require('http')
const { cpus } = require('os')
const numCPUs = cpus().length
if (cluster.isPrimary) {
  console.log(`Primary ${process.pid} is running`)
  // Fork workers.
  for (let i = 0; i < numCPUs; i++) {
    cluster.fork()
  }
  cluster.on('exit', (worker, code, signal) => {
    console.log(`worker ${worker.process.pid} died`)
  })
} else {
  // Workers can share any TCP connection
  // In this case it is an HTTP server
  http.createServer((req, res) => {
    res.writeHead(200)
    res.end('hello world\n')
  }).listen(8000)
  console.log(`Worker ${process.pid} started`)
}
/* 会自动重新执行自身
Primary 25020 is running
Worker 25021 started
Worker 25022 started
Worker 25024 started
Worker 25023 started
Worker 25025 started
Worker 25027 started
Worker 25026 started
*/

const cluster = require('cluster')
const http = require('http')
const { cpus } = require('os')
if (cluster.isPrimary) {
  // Keep track of http requests
  let numReqs = 0
  setInterval(() => {
    console.log(`numReqs = ${numReqs}`)
  }, 1000)
  // Count requests
  function messageHandler (msg) {
    if (msg.cmd && msg.cmd === 'notifyRequest') {
      numReqs += 1
    }
  }
  // Start workers and listen for messages containing notifyRequest
  const numCPUs = cpus().length
  for (let i = 0; i < numCPUs; i++) {
    cluster.fork()
  }
  for (const id in cluster.workers) {
    cluster.workers[id].on('message', messageHandler)
  }
} else {
  // Worker processes have a http server.
  http.Server((req, res) => {
    res.writeHead(200)
    const pid = process.pid
    res.end('process.pid' + pid)
    // Notify primary about the request
    process.send({ cmd: 'notifyRequest' })
  }).listen(3000)
}