Error: bind EADDRINUSE when hot module replacement enabled in neutrino node

Question

I'm using neutrino node.js preset with hot module replacement enabled, here's what I have in index.js:

import fastify from 'fastify'
import router from './router'

const ft = fastify()

ft.register(router)

// enable hot module replacement
if (module.hot) {
  module.hot.accept()
}

// listen
ft.listen(3000, 'localhost', (err) => {
  if (err) throw err
  console.log(`server listening on ${ft.server.address().port}`)
})

When I edit a file, I would got this:

I'm wondering if it is possible to use hot module replacement like this? Anyone have experience?

Thank you.

Answer 1

When using HMR with Node.js, it is a little trickier than with web projects since reloading the top-level file would mean needing to restart the process.

If you take note from the Neutrino docs on HMR in Node.js, you'll see that HMR isn't performed on the top-level index.js file, but rather on items that index.js imports.

Therefore, you'll want to accept specific things index.js imports, and use those from within, instead of trying to reload index.js which won't work without restarting the process.

if (module.hot) {
  module.hot.accept('./router');
  // Optionally use a function to re-bind functionality
  // after the accept:
  // module.hot.accept('./router', () => /* ... */);
}