创建一个线程池

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

// This will only be called if we're the master node.
// In a real app, you'd probably want to do something more
// like create a worker for every CPU (cluster.isMaster)
if (cluster.isMaster) {
  console.log(`Master ${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
  require('./server');

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