fix: keep waiting if connection is not ready to close

[Yangruipis]

related to #111

[Kludex]

I need more information here...

[Yangruipis]

Here is the way to reproduce this problem.

[Kludex]

If you can explain the problem, and the solution, it would save me time, and I'd really appreciate it.

[Yangruipis]

If you can explain the problem, and the solution, it would save me time, and I'd really appreciate it.

Sorry for my late response.

Problem

The close of the connection after timeout_keep_alive may raise error like that:

h11._util.LocalProtocolError: can't handle event type ConnectionClosed when role=SERVER and state=SEND_RESPONSE

Because the function timeout_keep_alive_handler is called when the connection is still sending data. This may happen with a very little probability under high concurrency, like a locust test.

uvicorn/uvicorn/protocols/http/h11_impl.py

Lines 352 to 360 in c3c2db3

	def timeout_keep_alive_handler(self) -> None:
	"""
	Called on a keep-alive connection if no new data is received after a short
	delay.
	"""
	if not self.transport.is_closing():
	event = h11.ConnectionClosed()
	self.conn.send(event)
	self.transport.close()

Solution

1. if the connection is still sending data, do not close it
2. (optional) put it back to the loop, which will be called after another timeout. Or we do nothing until another timeout_keep_alive_task is launched on response complete.

uvicorn/uvicorn/protocols/http/h11_impl.py

Lines 352 to 366 in 47475dd

	def timeout_keep_alive_handler(self) -> None:
	"""
	Called on a keep-alive connection if no new data is received after a short
	delay.
	"""
	if not self.transport.is_closing() and self.cycle.response_complete:
	event = h11.ConnectionClosed()
	self.conn.send(event)
	self.transport.close()
	# keep waiting if not ready
	elif not self.cycle.response_complete:
	self.timeout_keep_alive_task = self.loop.call_later(
	self.timeout_keep_alive, self.timeout_keep_alive_handler
	)

[Kludex]

I cannot reproduce your example. Are you able to create a test case on this PR?

[Yangruipis]

I cannot reproduce your example. Are you able to create a test case on this PR?

I have added a new case and some comments. But it's interesting that the new case passed locally, but failed in CI. I'll check my local package version firstly, and reopen this PR if I can make sure about it.

However, if you want to reproduce this issue, just run the new test case with the master branch code. It will raise error like that: