Lifespan question

[cardosofede]

Hey, First of all thanks for this initiative, it's great!
I have a question regarding the lifespan to manage objects.
Let's say that I would like to provide realtime data, and I have an object that subscribes via ws and keeps certain data updated, so I can expose a route to provide this data aggregated. Should I create the object with the lifespan approach? Or which is your recommendation?

[Praveenstein]

Great question, I'm curious for the reply by experts, been working on something similar.

[Kludex]

Can you give me an MRE? (GitHub repository with minimal setup would be great.)

[Kludex]

I'll reopen if you reply.

[cardosofede]

Sorry I just saw the message, will create one tomorrow

[cardosofede]

@Kludex hey, I have an example here: https://github.com/hummingbot/backend-api/blob/feat/add_market_data/routers/manage_market_data.py

I'm thinking about creating an endpoint to start a candles and stop the candles from a collection and if you ask for the realtime candles instead of creating and initializing the object will be just using the active candles.

As a reference, this is the class that we use in Hummingbot to keep the most updated length required of candles that are running: https://github.com/hummingbot/hummingbot/blob/master/hummingbot/data_feed/market_data_provider.py

[cardosofede]

hey @Kludex sorry for bothering you, but I'm upgrading some parts of this simple API: https://github.com/hummingbot/backend-api and I found that I have functions on_start and on_shutdown and based on the docs the best way to initialize those resources is through a lifespan: https://fastapi.tiangolo.com/advanced/events/

In my case I'm using routers to separate the app, but the lifespan has to be passed when I create the instance of the App, so what will be the best way to share the resources that I initialize in the main app to the routers?

thank you very much in advance and thanks for the great work!

[GameSetAndMatch]

@cardosofede In your lifespan you can instantiate singletons of resources (I.E.: httpx async client, and then pass them using Depends directly on your routes. See the docs for dependencies: https://fastapi.tiangolo.com/reference/dependencies/?h=depends#depends