support @asynccontextmanager app_factory functions
Author: graingertCreated Aug 13, 2021Updated Oct 27, 2025
Checklist
- There are no similar issues or pull requests for this yet.
- I discussed this idea on the community chat and feedback is positive.
Is your feature related to a problem? Please describe.
Currently the lifespan task runs in a sibling task to any request tasks, but a number of use cases require wrapping a context manager around all the request tasks, eg:
Describe the solution you would like.
support app factories like this:
@contextlib.asynccontextmanager
async def app_factory() -> AsyncGenerator[App, None]:
async with anyio.create_task_group() as tg:
app = FastAPI(__name__)
app.include_router(items.router)
yield appor :
var: ContextVar[int] = ContextVar('var', default=42)
@contextlib.asynccontextmanager
async def app_factory():
token = var.set(999)
try:
app = FastAPI(__name__)
app.include_router(items.router)
yield app
finally:
var.reset(token)or including the __aenter__/__aexit__ directly on the app instance:
class ACMGRFastAPI(FastAPI):
async def __aenter__(self) -> "ACMGRFastAPI":
async with AsyncExitStack() as stack:
self.database = stack.enter_async_context(database())
self.cache = stack.enter_async_context(cache())
self.bot = stack.enter_async_context(bot())
self._stack = stack.pop_all()
return self
async def __aexit__(self, *exc_info) -> bool | None:
return await self._stack.__aexit__(*exc_info)Describe alternatives you considered
run lifespan as a parent task to all the request tasks
Additional context
see https://gitter.im/encode/community?at=610989bc8fc359158c4f959e
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Source: Kludex/uvicorn