Add support for HTTP/2

[Zerotask]

I just did a test with Lighthouse (Desktop) and it showed incredibely nice results on the first try. This is really awesome.

For the Performance section the major penalty was missing HTTP\2

Describe the solution you'd like
I'd like to have an option to activate HTTP\2 via config.

[Conduitry]

I'm adding the pkg:adapter-node label to this, because I don't think the question of supporting HTTP/2 really makes sense in other contexts.

[dreitzner]

This is currently not possible as polka (current server in use) does not support http2.

Maybe we can get a polka update with an http2 option....

[Zerotask]

I created a feature request there: lukeed/polka#162

Since http2 is already supported by Node.js, it's more a framework and design decision for polka.

edit:
I noticed that the last human commit is from Aug 17, 2020. So as an alternative, we could also consider using a more up to date framework which already supports HTTP\2 like https://github.com/fastify/fastify

Hi there, it's already supported.
Do the exact same thing as the https example, but use the http2 module instead of the https module.
Once you create your own server, you pass it into your (main) Polka instance as options.server
Hope that helps~!

[jycouet]

With this doc: https://github.com/sveltejs/kit/tree/master/packages/adapter-node#custom-server
The issue is outdated no?

[bluepuma77]

The pull request was denied, one of the reasons was TLS. Maybe it would be possible to start without TLS?

Enable HTTP/2.0 (h2c) without TLS in SvelteKit, so users can benefit from decreased latencies and improved page load speeds. With this the usual reverse proxy can handle TLS, and we can still benefit from the http/2 speed improvements on the internal network.

Reference: HTTP/2.0 h2c on Wikipedia

[aradalvand]

@bluepuma77 Your best bet is just using a custom server, they're not gonna add built-in support for this.

[dlebech]

http/2 in unencrypted cleartext (h2c) works on Node 20.12.0 and earlier with a custom polka server. Support broke between v20.12.0 to v20.12.1, which was discussed over here: #11365 (comment)

Anyway, for the record, here is how I run h2c on node v20.12.0:

1. Create a server.js file at the root of your sveltekit project
2. Use the following contents:

import polka from 'polka';
import http2 from 'node:http2';
import { handler } from './build/handler.js';
import { env } from './build/env.js';

const path = env('SOCKET_PATH', false);
const host = env('HOST', '0.0.0.0');
const port = env('PORT', !path && '3000');

// Note: http2.createServer() is unencrypted and will not work in any browser
// This server should be behind a reverse proxy (eg. NGINX) with SSL termination.
const server = polka({ server: http2.createServer() })
  .use(handler)
  .listen({ path, host, port }, () => {
    console.log(`Listening on ${path ? path : host + ':' + port}`);
  });

const sessions = new Set();

server.server.on('session', (session) => {
  sessions.add(session);
  session.on('close', () => {
    sessions.delete(session);
  });
});

function shutdown() {
  server.server.close(() => {
    console.log('Server has closed.');
  });

  for (const session of sessions) {
    session.close();
  }
}

process.on('SIGTERM', shutdown);
process.on('SIGINT', shutdown);
process.on('exit', () => {
  console.log('Process is exiting.');
});

4. To test locally
   1. Run with e.g. PORT=1234 node server.js
   2. Use curl command curl -i --http2-prior-knowledge http://localhost:1234

Again, the above will only work in Node 20.12.0 and below, unfortunately. Running an old version of Node is probably not the best idea long-term, so it would be nice with a better solution for h2c http/2.

(PS. I'm using Google Cloud Run for end-to-end http/2 which requires h2c for it to work)