Handling app.state changes on db changes

[NixBiks]

Hi,

I'm new to litestar but it looks very neat. I have question about best practice for a use case I have.

I need to sync some data from my DB to app.state (low-latency requirements).

I imagine adding lifespan context manager where I connect to the db, fetch initial data, set the initial app.state as well as setting up a websocket between the DB and my application - on each read I then need to update app.state but I'm not sure how to do this in a safe manner.

Any pointers for me?

[Alc-Alc]

Can you explain what you mean by "safe manner"? If you mean protection against data races, assignment to state via indexing (state["something"] = "some value") and via attribute (state.something = "somevalue") are protected with a lock making it thread safe. As for "async safe", nothing special has to be done because there is no context switching / async operations inside the setters.

[Alc-Alc]

Relevant code

litestar/litestar/datastructures/state.py

Lines 254 to 280 in de8f4a7

	def __setitem__(self, key: str, value: Any) -> None:
	"""Set an item in the state using subscription notation.
	Args:
	key: Key to set.
	value: Value to set.
	Returns:
	None
	"""
	with self._lock:
	self._state[key] = value
	def __setattr__(self, key: str, value: Any) -> None:
	"""Set an item in the state using attribute notation.
	Args:
	key: Key to set.
	value: Value to set.
	Returns:
	None
	"""
	with self._lock:
	self._state[key] = value