Node.js 中的集群模块如何工作

Node.js是一个基于事件驱动的JavaScript运行时环境，可以在服务器端运行JavaScript代码。在Node.js中，可以使用集群模块来利用多个进程来处理并发请求，从而提高服务器的性能和可扩展性。集群模块允许将工作负载分布到多个工作进程中，每个进程都可以独立地处理请求，并共享服务器的端口。

javascript
const cluster = require('cluster');
const http = require('http');
const numCPUs = require('os').cpus().length;
if (cluster.isMaster) {
  console.log(`Master ${process.pid} is running`);
  // 创建工作进程
  for (let i = 0; i < numCPUs; i++) {
    cluster.fork();
  }
  cluster.on('online', (worker) => {
    console.log(`Worker ${worker.process.pid} is online`);
  });
  cluster.on('exit', (worker, code, signal) => {
    console.log(`Worker ${worker.process.pid} died with code ${code} and signal ${signal}`);
    console.log('Starting a new worker');
    cluster.fork();
  });
} else {
  // 创建HTTP服务器
  http.createServer((req, res) => {
    res.writeHead(200);
    res.end('Hello World\n');
  }).listen(8000);
  console.log(`Worker ${process.pid} started`);
}

javascript
const cluster = require('cluster');
const http = require('http');
const numCPUs = require('os').cpus().length;
if (cluster.isMaster) {
  console.log(`Master ${process.pid} is running`);
  // 创建工作进程，并指定负载均衡算法
  for (let i = 0; i < numCPUs; i++) {
    cluster.fork({ 'CLUSTER_SCHED_POLICY': 'least-connection' });
  }
  // ...
}