HMR "before reload" hook possible?

[enso-media]

Im developing an application that is able to spawn individual processes for specific integrations.
The main app has a service thats manages those integration processes and is able to start and stop them. This i done by using nodes child processes and fork() an adonis ace command that runs an integration.

Everything works well so far, except for some annoying problems when using HMR while developing:
Some of those integrations for example communicate with hardware via an own TCP server on a specific port that is started by the process.
Now when i change anything in the source adonis hot reloads, but the forked processes keeps running and gets restarted again, resulting in "address/port already in use" for the started TCP server.

Now im trying to find a solution to hook into the HMR lifecycle before it reloads, so that i can gracefully exit running child processes and close server connections to avoid those problems.

As Adonis using its own HMR i cannot use vite events.
There is the "onSourceFileChanged" assembler hook in adonisrc that i hoped i can use, however nothing happened as it seemed that it doesnt get triggered for HMR changes.

Any recommendations how to solve this?

[Julien-R44]

Two options available. Check out the docs : https://github.com/Julien-R44/hot-hook#api

• import.meta.decline() -> this forces a full server reload when the file containing this line is changed
• import.meta.dispose(() => cleanup()) -> lets you run some cleanup logic before hot-reloading kicks in

[enso-media]

Thanks for the answer. Ive already seen this, but that doesnt work. No matter where i define this dispose callback, it never gets triggered.
Also it doesnt help when the child processes running forked as an ace command not having HMR, and theyre tracked and managed in a singleton service class instance in my core app.
I need some kind of global event i can listen to in my integration service, so it can end all currently running child processes before a reload. Something like in vites HMR api: hot.on('vite:beforeUpdate')

[thetutlage]

May I know why you want to close and re-run child processes on a hot-reload? Because, you could run them only once (when the dev server starts) and let them continue to run forever, until the dev server is restarted (not hot-reloaded)

[enso-media]

@thetutlage, my "integrations" carrying most of the apps logic and due to this also undergoing the most code changes. So theyre the parts that continously needs to be reloaded/restarted for developing and debugging. The core app is only needed for the process management and communication between the integrations. The child processes are tracked in memory at runtime within a singleton service class. So when the app reloads/restarts i lose all information on those processes and im not able anymore to track their state or control them.

I just got a bit deeper in the rabbit hole looking at the hot-hook documentation...
My integrations each have their own folder (almost like an adonis package) that again lies in an "integrations" folder on root level.
But as it seems by default only very few files (controllers, middleware) are added to the hot-hook boundaries.
So i almost always get a full-reload on file changes. Thats ok, as a real HMR is not possible anyway due to the fact that im running child processes.
But the problem stays that i need some way to get a "before reload" hook, so my integration service can end the current child processes, so that i dont lose track of them and theyre not getting forked multiple times.