run.js

#!/usr/bin/env node
/**
 * Node.js API Starter Kit (https://reactstarter.com/nodejs)
 *
 * Copyright © 2016-present Kriasoft, LLC. All rights reserved.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE.txt file in the root directory of this source tree.
 */

const fs = require('fs');
const path = require('path');
const cp = require('child_process');
const pkg = require('../package.json');
const task = require('./task');

let build;
let server;
let debugPort = '9230';

const serverQueue = [];
const isDebug = process.execArgv.some(x => x.startsWith('--inspect'));

// Gracefull shutdown
process.once('cleanup', () => {
  if (server) {
    server.addListener('exit', () => process.exit());
    server.kill('SIGTERM');
    serverQueue.forEach(x => x.kill());
  } else {
    process.exit();
  }
});
process.on('SIGINT', () => process.emit('cleanup'));
process.on('SIGTERM', () => process.emit('cleanup'));

// Ensure that Node.js modules were installed,
// at least those required to build the app
try {
  build = require('./build');
} catch (err) {
  if (err.code !== 'MODULE_NOT_FOUND') throw err;
  // Install Node.js modules with Yarn
  cp.spawnSync('yarn', ['install', '--no-progress'], { stdio: 'inherit' });

  // Clear Module's internal cache
  try {
    const Module = require('module');
    const m = new Module();
    // eslint-disable-next-line
    m._compile(fs.readFileSync('./tools/build.js', 'utf8'), path.resolve('./tools/build.js'));
  } catch (error) { } // eslint-disable-line

  // Reload dependencies
  build = require('./build');
}

// Launch `node build/server.js` on a background thread
function spawnServer() {
  return cp.spawn('node',
    [
      // Pre-load application dependencies to improve "hot reload" restart time
      ...Object.keys(pkg.dependencies).reduce((requires, val) => requires.concat(['--require', val]), []),
      // If the parent Node.js process is running in debug (inspect) mode,
      // launch a debugger for Express.js app on the next port
      ...process.execArgv.map((arg) => {
        if (arg.startsWith('--inspect')) {
          const match = arg.match(/^--inspect=(\S+:|)(\d+)$/);
          if (match) debugPort = Number(match[2]) + 1;
          return `--inspect=${match ? match[1] : '0.0.0.0:'}${debugPort}`;
        }
        return arg;
      }),
      '--no-lazy',
      // Enable "hot reload", it only works when debugger is off
      ...(isDebug ? ['./server.js'] : [
        '--eval',
        'process.stdin.on("data", data => { if (data.toString() === "load") require("./server.js"); });',
      ]),
    ],
    { cwd: './build', stdio: ['pipe', 'inherit', 'inherit'], timeout: 3000 });
}

module.exports = task('run', () => Promise.resolve()
  // Migrate database schema to the latest version
  .then(() => {
    cp.spawnSync('node', ['tools/db.js', 'migrate'], { stdio: 'inherit' });
  })
  // Compile and launch the app in watch mode, restart it after each rebuild
  .then(() => build({
    watch: true,
    onComplete() {
      if (isDebug) {
        if (server) {
          server.on('exit', () => { server = spawnServer(); });
          server.kill('SIGTERM');
        } else {
          server = spawnServer();
        }
      } else {
        if (server) server.kill('SIGTERM');
        server = serverQueue.splice(0, 1)[0] || spawnServer();
        server.stdin.write('load'); // this works faster than IPC
        if (server) while (serverQueue.length < 3) serverQueue.push(spawnServer());
      }
    },
  }))
  // Resolve the promise on exit
  .then(() => new Promise((resolve) => {
    process.once('exit', () => {
      if (server) server.kill();
      resolve();
    });
  })));