resilent fault-tolerant server with cluster

server.js

/* eslint-disable no-console */
/* eslint-disable no-param-reassign */

const os = require('os');
const graceful = require('graceful');
const cluster = require('cluster');
const app = require('../app');

const isDev = process.env.NODE_ENV === 'development';

if (cluster.isMaster) {
  const workers = isDev ? 1 : os.cpus().length;
  console.log(`Master cluster setting up ${workers} workers...`);

  for (let i = 0; i < workers; i += 1) {
    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();
  });

  process.on('exit', (code) => {
    console.log(`cluster about to exit with code: ${code}`);
  });
  process.on('uncaughtException', (err) => {
    console.log(`Caught exception: ${err}`);
  });
} else if (cluster.isWorker) {
  // 不要修改默认端口号
  // 6001 是集团服务器 Node.js 服务默认端口号
  const SERVER_NODEJS_PORT = 6001;
  const LOCAL_PORT = 7001;

  let port = isDev ? LOCAL_PORT : SERVER_NODEJS_PORT;
  // 支持命令行传入 port: `npm run hot-server -- port=7001`
  // console.log(`process.argv:`, process.argv);
  // port=7001
  const matches = process.argv[2] && process.argv[2].match(/port=(\d{4})/);
  if (matches) port = Number(matches[1]);

  const server = app.listen(port, () => {
    console.log(`Server listening on port ${server.address().port}`);
  });

  graceful({
    server,
    killTimeout: 30 * 1000,
    error(err, throwErrorCount) {
      if (err.message) {
        err.message += ` (uncaughtException throw ${throwErrorCount} times on pid:${process.pid})`;
      }
      console.error(err);
    },
  });
}