server.js

import * as fs from 'node:fs';
import * as path from 'node:path';
import * as url from 'node:url';

import { createRequestHandler } from '@remix-run/express';
import { broadcastDevReady, installGlobals } from '@remix-run/node';
import compression from 'compression';
import express from 'express';
import morgan from 'morgan';
import sourceMapSupport from 'source-map-support';

sourceMapSupport.install();
installGlobals();

/** @typedef {import('@remix-run/node').ServerBuild} ServerBuild */

const BUILD_PATH = path.resolve('build/index.js');
const VERSION_PATH = path.resolve('build/version.txt');

const initialBuild = await reimportServer();
const remixHandler =
  process.env.NODE_ENV === 'development'
    ? await createDevRequestHandler(initialBuild)
    : createRequestHandler({
        build: initialBuild,
        mode: initialBuild.mode,
      });

const app = express();

app.use(compression());

// http://expressjs.com/en/advanced/best-practice-security.html#at-a-minimum-disable-x-powered-by-header
app.disable('x-powered-by');

// Remix fingerprints its assets so we can cache forever.
app.use(
  '/build',
  express.static('public/build', { immutable: true, maxAge: '1y' }),
);

// Everything else (like favicon.ico) is cached for an hour. You may want to be
// more aggressive with this caching.
app.use(express.static('public', { maxAge: '1h' }));

app.use(morgan('tiny'));

app.all('*', remixHandler);

const port = process.env.PORT || 3000;
app.listen(port, async () => {
  console.log(`Express server listening on port ${port}`);

  if (process.env.NODE_ENV === 'development') {
    broadcastDevReady(initialBuild);
  }
});

/**
 * @returns {Promise<ServerBuild>}
 */
async function reimportServer() {
  const stat = fs.statSync(BUILD_PATH);

  // convert build path to URL for Windows compatibility with dynamic `import`
  const BUILD_URL = url.pathToFileURL(BUILD_PATH).href;

  // use a timestamp query parameter to bust the import cache
  return import(BUILD_URL + '?t=' + stat.mtimeMs);
}

/**
 * @param {ServerBuild} initialBuild
 * @returns {Promise<import('@remix-run/express').RequestHandler>}
 */
async function createDevRequestHandler(initialBuild) {
  let build = initialBuild;
  async function handleServerUpdate() {
    // 1. re-import the server build
    build = await reimportServer();
    // 2. tell Remix that this app server is now up-to-date and ready
    broadcastDevReady(build);
  }
  const chokidar = await import('chokidar');
  chokidar
    .watch(VERSION_PATH, { ignoreInitial: true })
    .on('add', handleServerUpdate)
    .on('change', handleServerUpdate);

  // wrap request handler to make sure its recreated with the latest build for every request
  return async (req, res, next) => {
    try {
      return createRequestHandler({
        build,
        mode: 'development',
      })(req, res, next);
    } catch (error) {
      next(error);
    }
  };
}