Socket Activation

[waynebloss]

Just wondering if anyone has any experience with socket activation via systemd (Linux) or launchd (macOS)?

I have not tested the following yet, but I think it will work.

Any thoughts or notes? If I'm correct, you can't pass an fd to node's http.createServer, but you can pass it to listen, so we must patch the returned server's listen method... Also, any options passed to server.listen() by Fastify are thrown out, except for backlog...

const fastify = Fastify({
  /**
   * Example to use socket activation, via file descriptor via something like
   * https://github.com/sorccu/node-socket-activation
   */
  serverFactory(handler, opts: FastifyServerOptions) {
    const server = http.createServer(handler);
    // const coreListen = server.listen as net.Server["listen"]; // overload 7
    const coreListen = server.listen as (...args: any[]) => Http.Server;
    Object.assign(server, {
      listen(options: net.ListenOptions, cb?: () => void) {
        const fd = 3; // TODO: Get fd from socket-activation lib...
        if (options.backlog) {
          coreListen.call(server, { fd }, options.backlog, cb);
        } else {
          coreListen.call(server, { fd }, cb);
        }
        return server;
      },
    });
    return server;
  },
  // ...
});

[metcoder95]

Never tried socket-activation before (but thanks for the item to my reading list though). But fastify sanitizes the listen arguments before calling the serverFactory (either custom or the HTTP one from Node). See reference:

fastify/lib/server.js

Line 305 in c068697

function normalizeListenArgs (args) {

That being said, at the given state you'll need to pass through the closure of the listen method, the fd to forward it.
Not sure why fastify doesn't support it, but most likely due to security concerns 🙂

[waynebloss]

Thanks for your input! I rewrote my notes from last night's experiment in order to make them more generic.

Systemd Socket Activation for PWA

• https://gist.github.com/waynebloss/63b4a8a326c4ef4e5db24a209eab5882

[waynebloss]

(In my gist above, I just used a proxy service to forward all HTTP requests instead of opening an fd, but I may try it out with the fd technique.)

[metcoder95]

Sounds interesting and funny. Thanks for the notes, makes a quick sum up of the topic 🙂
Towards fastify that's the only way to bypass the sanitization for passing the fd down to the HTTP server creation. Let us know if you were able to make it work 🤞

[climba03003]

You can start fastify with fastify.listen({ fd: 3 }).
The normalization is used to support old multiple arguments that will be deprecated in next major.