aio-libs / aiohttp-sse

I am having to do

        try:
            async with sse_response(request) as response:
                async for event in self.execute_workflow(
                    layers, caller_user, resolved_workflow, payload
                ):
                    await response.send(json.dumps(event.to_json()))
        except asyncio.CancelledError:
            # aiohttp_sse is not handling the finishing of the response properly
            # and it is raising an internal CancelledError used for stopping the
            # response. We have to catch it and ignore it.
            logger.debug(
                "Ignoring cancelled error in streaming workflow request", exc_info=True
            )

And if we look at the exc info it is happening inside the lib:

Ignoring cancelled error in streaming workflow request
Traceback (most recent call last):
  File "/opt/isolate_controller/projects/isolate_controller/isolate_controller/gateway/_gateway.py", line 1071, in streaming_workflow_request
    async with sse_response(request) as response:
  File "/usr/local/lib/python3.11/site-packages/aiohttp_sse/helpers.py", line 61, in __aexit__
    return await self._obj.__aexit__(exc_type, exc, tb)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/aiohttp_sse/__init__.py", line 221, in __aexit__
    await self.wait()
  File "/usr/local/lib/python3.11/site-packages/aiohttp_sse/__init__.py", line 147, in wait
    await self._ping_task
  File "/usr/local/lib/python3.11/site-packages/aiohttp_sse/__init__.py", line 203, in _ping
    await asyncio.sleep(self._ping_interval)
  File "/usr/local/lib/python3.11/asyncio/tasks.py", line 649, in sleep
    return await future
           ^^^^^^^^^^^^
asyncio.exceptions.CancelledError

aiohttp-sse/aiohttp_sse/__init__.py

Lines 138 to 162 in e2f46bf

    
               async def wait(self) -> None: 
        
                   """EventSourceResponse object is used for streaming data to the client, 
        
                   this method returns future, so we can wait until connection will 
        
                   be closed or other task explicitly call ``stop_streaming`` method. 
        
                   """ 
        
                   if self._ping_task is None: 
        
                       raise RuntimeError("Response is not started") 
        
                   try: 
        
                       await self._ping_task 
        
                   except asyncio.CancelledError: 
        
                       if ( 
        
                           sys.version_info >= (3, 11) 
        
                           and (task := asyncio.current_task()) 
        
                           and task.cancelling() 
        
                       ): 
        
                           raise 
        
               def stop_streaming(self) -> None: 
        
                   """Used in conjunction with ``wait`` could be called from other task 
        
                   to notify client that server no longer wants to stream anything. 
        
                   """ 
        
                   if self._ping_task is None: 
        
                       raise RuntimeError("Response is not started") 
        
                   self._ping_task.cancel()

I do not see any other source of CancelledError being riased in my code, so I am thinking this is somehow maybe getting the wrong reference in asyncio.current_task()?

Can you create an actual reproducer? The test cases we have all seem to be working correctly.

so I am thinking this is somehow maybe getting the wrong reference in asyncio.current_task()?

I don't see how that's possible.

I spent some time and cannot create a reproducer. I will try to get around to do this eventually, but it just happened in my prod environment and I solved as described. We can close for now if you prefer and I can re open when I do it.

I don't mind. If there is an issue, I'd certainly like to resolve it. But, can't really imagine what's going wrong based on the current information.

Unless you are using handler_cancellation and forgot (or a rather old version of aiohttp where it was on by default)? https://docs.aiohttp.org/en/stable/web_advanced.html#web-handler-cancellation

	async def wait(self) -> None:
	"""EventSourceResponse object is used for streaming data to the client,
	this method returns future, so we can wait until connection will
	be closed or other task explicitly call ``stop_streaming`` method.
	"""
	if self._ping_task is None:
	raise RuntimeError("Response is not started")

	try:
	await self._ping_task
	except asyncio.CancelledError:
	if (
	sys.version_info >= (3, 11)
	and (task := asyncio.current_task())
	and task.cancelling()
	):
	raise

	def stop_streaming(self) -> None:
	"""Used in conjunction with ``wait`` could be called from other task
	to notify client that server no longer wants to stream anything.
	"""
	if self._ping_task is None:
	raise RuntimeError("Response is not started")
	self._ping_task.cancel()

Having to handle CancelledError instead of it working automatically