Update eject example to something more robust

[lord007tn]

Prerequisites

• I have written a descriptive issue title
• I have searched existing issues to ensure the feature has not already been requested

🚀 Feature Proposal

Change the eject file example to validate everything before running the server and make use of the .ready() function.

Motivation

What made me think of this approach are:

• Fastify encapsulation concept, the server should not run if something goes wrong with plugins and are not loaded inside correctly inside Fastify.
• The struggle I've been in the past few days trying to use Fastify in a complex real-world project and I didn't find clear examples.
• easier to handle errors, if something goes wrong Fastify will throw the valid error not some error buried deep inside the router or hooks
• the unclear error "cannot read properties of undefined (reading 'length')" which was happening for several reasons and I cannot detect them until i throw error on startup

Example

// Read the .env file.
import * as dotenv from "dotenv";
dotenv.config();

// Require the framework
import Fastify from "fastify";

// Require library to exit fastify process, gracefully (if possible)
import closeWithGrace from "close-with-grace";

// Instantiate Fastify with some config
const app = Fastify({
  logger: true,
});
// make use of the `.ready()` to prevent going on race condition
fastify.register(app).ready((err) => {
   // throw error if something happened on registering `plugins` or `routes`
	if (err) throw err;
	// delay is the number of milliseconds for the graceful close to finish
	const closeListeners = closeWithGrace(
		{
			delay:
				parseInt(process.env.FASTIFY_CLOSE_GRACE_DELAY as string) ||
				500,
		},
		async function ({ signal, err, manual }) {
			if (err) {
				fastify.log.error(err);
			}
			await fastify.close();
		} as closeWithGrace.CloseWithGraceAsyncCallback
	);
	fastify.addHook("onClose", async (instance, done) => {
		closeListeners.uninstall();
		done();
	});
	//server listen
	const port = process.env.PORT || 8000;
	// Start listening.
	fastify.listen({ port: parseInt(port as string) }, (err: any) => {
		if (err) {
			fastify.log.error(err);
			process.exit(1);
		}
	});
});

[lord007tn]

@mcollina what are your thoughts about that?

[mcollina]

I would move the close-with-grace setup inside the listen callback instead.

[lord007tn]

could you explain more why?
as i know you cant have addHook inside listen

[mcollina]

Ah sorry, I think I misunderstood your example.

I don't think close-with-grace should be within a plugin or a callback, but rather at the top level, installed after the server has been setup.

It's a property of the global application and not of the server, and you can install only one. Therefore, you should put that into the "main" of your application outside of all plugins.