request tuto/method how to debug unclosed sessions on exit about aiohttp HOT 7 CLOSED

This isn't really an issue with aiohttp, it's an issue with your architecture/coding practices.

If you always use async with when creating a session, then you won't have any unclosed sessions. Alternatively, I've seen libraries that provide context manager stacks as part of an application's lifecycle (maybe combined with dependency injection). You can use a linting rule or something to enforce this usage across your code.

from aiohttp.

@Dreamsorcerer

Thanks for your prompt reply.

While I know that async with is the recommended pratice, there are situations where we might be called upon to debug code outside of our control, such as code written by others or in third party modules. (aiohttps is used by many third party aio modules).

Unfortunately, when these external sources don't use async with, it can be challenging to identify the unclosed sessions.

Only after pingpointing these unclose sessions, can we suggest adpoting async with as a best pratice.

So I think this is real use case.

from aiohttp.

Hmm, the issue is much the same as any other asyncio primitive, so we should probably do the same as asyncio does or suggest similar changes there.

The only thing I can think of is to get the current traceback when the object is initialised and then include that in the warning. This would probably need to be done only when using debug mode to avoid the overhead.

from aiohttp.

If you want to give it a go, it'd probably look something like:

from aiohttp.helpers import DEBUG

if DEBUG:
    self._tb = traceback.extract_stack()

from aiohttp.

hello,

Do you mean save the traceback stack during the session __init__ if DEBUG mode is on, and display it in the error message as follows ?

Like:

class ClientSession:
    def __init__(
        self,
        ...
    ) -> None:
+       if DEBUG:
+           import traceback
+           self._tb = traceback.extract_stack()
        ...

    def __del__(self, _warnings: Any = warnings) -> None:
        if not self.closed:
            kwargs = {"source": self}
            _warnings.warn(
                f"Unclosed client session {self!r}", ResourceWarning, **kwargs
            )
            message = "Unclosed client session"
+           if DEBUG:
+               message += f"\nSession creation traceback stack: {self._tb}"
            context = {"client_session": self, "message": message}
            if self._source_traceback is not None:
                context["source_traceback"] = self._source_traceback
            self._loop.call_exception_handler(context)

from aiohttp.

That was my suggestion, yes. Feel free to make a PR if you've got it working. Will need a test to show it's working correctly too (needs to be marked with @pytest.mark.dev_mode).

from aiohttp.

sorry, I just found it's already been implemented, when setting the env var PYTHONASYNCIODEBUG=1, the unclosed session gives already the creation traceback, all is good now, thank for your help.

from aiohttp.