accessing app state on startup/shutdown handlers

i have a starlette app that uses @app.[route|on_event] decorators for routing but would like to switch to the recommended Starlette(routes=..., on_startup=...).

one thing i’m confusing about: how can i access app state via startup/shutdown handlers? currently i have the following:

from my_middleware import GetDatabaseConnectionMiddleware

app = Starlette()
# some middleware that gets a connection from app.state.connection_pool
# and adds it to the request's scope
app.add_middleware(GetDatabaseConnectionMiddleware)

@app.on_event("startup")
async def startup():
    app.state.connection_pool = await asyncpg.create_pool(
        dsn=DATABASE_URL, min_size=2, max_size=2
    )

i think this is a bit messy but seemed like the most obvious way to set app state in the startup handler. i’m not sure how i’d do the same when app is created after the functions are defined, though. any ideas on how to do this?

[tomchristie]

i’m not sure how i’d do the same when app is created after the functions are defined, though. any ideas on how to do this?

You can define the startup function before the application instantation. That’s fine, since it won’t run until the app is in scope.

async def startup():
    app.state.connection_pool = await asyncpg.create_pool(
        dsn=DATABASE_URL, min_size=2, max_size=2
    )

app = Starlette(routes=..., middleware=..., on_startup=[startup])

[tomchristie]

@laurentS Yup I think that’s reasonable. I’ve got an outstanding PR for a context-managed. lifespan alternative to startup/shudown, and yes, that happens to include the app instance… https://github.com/encode/starlette/pull/799