Fastify hot-reload during development

[hugoattal]

So, I know that Fastify kinda "compiles" route and plugins for fast access before listening to request.
And I absolutely love Fastify for that, as I want a fast backend in production.

However, it can be a bit frustrating during development. I don't really care that response are fast or not when I'm developing it in local.
For now, I use nodemon to restart my local Fastify server whenever I make a change. The thing is that's reaaaally slow. My server used to take more than a minute to get started, I optimized it a bit to come down to nearly 15s, but it's still a bit painful.

I wanted to know if you guys had an idea/solution/anything to make hot reload work during development? (like, in less than a second)
No worry if that's not possible, I'll 100% keep using Fastify, but just wanted to give it a shot.

(In any case, thanks so much to the whole team, you guys rock ❤️)

[zekth]

What kind of setup do you have? Js or Ts? I personnaly use nodemon with TS and it's like 10s-15s. Which is acceptable regarding the stack involved.

[hugoattal]

TS (and I use ts-node as CLI). Yes, 10-15s is acceptable, I'm just looking for a fast hot-reload. I'm using vite in the frontend, and I'm getting used to instant reload.
It's really just for comfort, it's not essential, but wanted to know if anyone had a solution for that.

[zekth]

incremental build also helps a lot and seems to be supported in ts-node now.

[mcollina]

I have been experimenting with
https://github.com/fastify/restartable and https://github.com/mcollina/fastify-isolate for similar reasons. It would be awesome to combine these and typescript to automatically recompile and reload.

[meotimdihia]

@mcollina hopefully, we can release it soon. It is kind of suck when the application is becoming bigger.

[mcollina]

If you are looking for this kind of flow, you can try platformatic service. Automatic live reload with TS recompilation.

[hugoattal]

I just add this message in case someone is looking to reduce startup speed during development:

You can just disable type checking (which remains active on your IDE of course), and it will drastically reduce startup time.
For this, just use the transpileOnly flag (shortcut T) on ts-node or nodemon.

Example:

> ts-node --transpileOnly src/index.ts
> ts-node -T src/index.ts

cf https://typestrong.org/ts-node/docs/options/#transpileonly