How do you handle settings?

[danechitoaie]

How do you handle loading settings from ENV and then making them available in the route handlers?

At the moment I'm using a BaseSettings class from pydantic. Is this the right way? And how do I make this available in all the route handlers that need it?

[rgajason]

We have created an AppSettings class based off BaseSettings. We then use dependency injection to make the settings available.

config.py

class AppSettings(BaseSettings):
    app_name: str = "My Awesome App"
    app_short_name: str = "awesome"
    admin_email: str = "[email protected]"
    mongodb_url: str
    mongodb_db: str

dependencies.py

@lru_cache()
def get_settings() -> AppSettings:
    return AppSettings()

main.py

app = Starlite(
    ...
    dependencies={
        "settings": Provide(get_settings, use_cache=True),
    },
)

Within a given controller, we can say something like:

async def my_endpoint(
    self,
    settings: AppSettings,
)

...and the settings variable holds our app settings.

Since this is based off Pydantic's BaseSettings we can use a mixture of default / hard-coded, environment variables, and .env files.

https://docs.litestar.dev/latest/usage/dependency-injection.html

https://docs.pydantic.dev/usage/settings/

[danechitoaie]

What happens with lru_cache if you use Redis caching? will those be cached in Redis and such on every request we will end up with unneeded requests to Redis to retrieve the settings when their values never change?

[provinzkraut]

lru_cache has nothing to do with Redis. It's a Python stdlib function: https://docs.python.org/3/library/functools.html#functools.lru_cache

[danechitoaie]

My bad. Awesome then. I confused this with the caching sport that the framework provides.
Only one more problem that I see with this approach is that the data validation (if the settings are provided or not) that pydantic does happens on request (first time that the dependency is used) vs happening on app startup.

Any way I can do this validation when/or before the app starts and not even start the app if I have some missing configs?

[provinzkraut]

You can just do settings = AppSettings() anywhere you want and then use that.