SIGINT Can't abort ASGI lifespan shutdown

[CNSeniorious000]

Sometimes ASGI app lifespan shutdown gets stuck, and users want to use Ctrl+C to escape it. In the current logic, if two SIGINTs were received before shutdown, it will skip shutdown.

But once we've entered await self.lifespan.shutdown() here:

uvicorn/uvicorn/server.py

Lines 290 to 294 in 6d26d88

	# Send the lifespan shutdown event, and wait for application shutdown.
	if not self.force_exit:
	await self.lifespan.shutdown()

handle_exit just keep pushing to self._captured_signals without further action.

uvicorn/uvicorn/server.py

Lines 333 to 338 in 6d26d88

	def handle_exit(self, sig: int, frame: FrameType | None) -> None:
	self._captured_signals.append(sig)
	if self.should_exit and sig == signal.SIGINT:
	self.force_exit = True # pragma: full coverage
	else:
	self.should_exit = True

I suggest that on the third SIGINT, we call cancel on the running shutdown task or other similar approach. And then self._captured_signals will be flushed and a harder exit would be possible.

Another approach may be checking force_exit during each wait in LifespanOn:

    async def wait(self, event: asyncio.Event):
        while not server.force_exit:  # may need to store the server ref in LifespanOn
            async with timeout(0.1):
                await event.wait()

And change await self.shutdown_event.wait() into await self.wait(self.shutdown_event)

---

Maybe related to:

• Finesse signals #158
• Shutdown process is broken in 0.15 #1160
• uvicorn eats SIGINTs, does not propagate exceptions #1579

[CNSeniorious000]

For example, this FastAPI app will hang 5 seconds and can't be skipped once started even if you keep sending SIGINT.

@asynccontextmanager
async def lifespan(_):
    yield
    print("Shutting down...")
    await sleep(5)
    print("Cleaned up.")

app = FastAPI(lifespan=lifespan)

[CNSeniorious000]

Note that this is not directly related to #1972. I use Windows but I can't reproduce #1972 on any version of python.