add mapping between client_token and socket id

[Lendemor]

Keep an internal mapping between client token and sid.

Can be used by end user to terminate some logic/tasks if the websocket associated with a given state is disconnected.

Will also be helpful later for some internal use.

Can be used like this to terminate a background task for example :

class State(rx.State):
    @rx.background
    async def loop_function(self):
        while True:
            if self.router.session.client_token not in app.event_namespace.token_to_sid:
                break
            await asyncio.sleep(2)


@rx.page(on_load=State.loop_function)
def index():
    return rx.text("Hello")

Possible improvement : Provide a "cleaner" access to this mapping for end user?

Close #3387

[picklelo]

LGTM - is there a concrete use case for this yet? Or just in case we need it later?

[Lendemor]

LGTM - is there a concrete use case for this yet? Or just in case we need it later?

Without this users can not terminate logic in background tasks, so I'd say yes.

but there will also be other potential future use too.

[5quinque]

How can you use this method if you have your app initialized in one module, and your State class defined in another?
If I want the background task to run when the page loads, there isn't a way without causing a circular import?

For example,

from app_name.state import State

app = rx.App()

app.add_page(component=chat_page(), route="/", on_load=State.background_event)

from app_name.app_name import app

class State(rx.State):
    @rx.event(background=True)
    async def background_event(self):
        while True:
            if self.router.session.client_token not in app.event_namespace.token_to_sid:
                ...

[benedikt-bartscher]

@5quinque maybe you can use get_app inside the handler?

[5quinque]

@5quinque maybe you can use get_app inside the handler?

Didn't know about this method, but it works perfectly, thanks :D