Do your infra hops respect HTTP 103 Early Hints?

early-hints-test.mjs

import * as http from 'node:http';
import { Readable } from 'node:stream';
import { setInterval } from 'node:timers/promises';

async function* chunksWhile(ms) {
  let count = 0;
  for await (const startTime of setInterval(1000, Date.now())) {
    yield `<div>Looking for your cat... (n=${++count})</div>`;
    if (Date.now() - startTime > ms) {
      return;
    }
  }
}

const server = http.createServer((req, res) => {
  if (req.url !== '/') {
    res.writeHead(404, { 'Content-Type': 'text/plain' });
    res.end('Not Found');
    return;
  }

  const stream = Readable.from(chunksWhile(5000));
  res.writeEarlyHints({
    link: '<https://cataas.com>; rel="preconnect"',
  });
  res.writeHead(200, {
    'Content-Type': 'text/html',
  });
  stream.pipe(res, { end: false });
  stream.on('end', () => {
    res.write(`<div>And here's your cat`);
    res.write('<div><img src="https://cataas.com/cat" /></div>');
    res.write('</div>');
    res.end();
  });
});

server.listen(3000);

process.on('SIGINT', () => {
  server.close(() => {
    process.exit(0);
  });
});