Error on application startup after adding pg_context to main.py

[DevMain1953]

Hello, I make polls application from docs. Version of PostgreSQL is 15. Using poetry here are my dependencies from pyproject.toml:

python = "^3.11"
aiohttp = "^3.8.5"
aiodns = "^3.0.0"
pyyaml = "^6.0.1"
aiopg = {extras = ["sa"], version = "^1.4.0"}

main.py:

app.cleanup_ctx.append(pg_context) # Added this

db.py

async def pg_context(app):
    conf = app['config']['postgres']
    engine = await aiopg.sa.create_engine(
        database=conf['database'],
        user=conf['user'],
        password=conf['password'],
        host=conf['host'],
        port=conf['port'],
        minsize=conf['minsize'],
        maxsize=conf['maxsize'],
    )
    app['db'] = engine

    yield

    app['db'].close()
    await app['db'].wait_closed()

If I remove app.cleanup_ctx.append(pg_context) from main.py server runs successfully. But when I try to run server python main.py I got such error (see below): What problem can it be?

From traceback: it says exception occurs when I do this engine = await aiopg.sa.create_engine(... in db.py.

(aiohttp-example-py3.11) F:\python\AIOHTTP\polls>python app_polls/main.py
unhandled exception during asyncio.run() shutdown
task: <Task finished name='Task-1' coro=<_run_app() done, defined at C:\Users\sergey\AppData\Local\pypoetry\Cache\virtualenvs\aiohttp-example-zDtRzW9K-py3.11\Lib\site-packages\aiohttp\web.py:289> exception=NotImplementedError()>
Traceback (most recent call last):
  File "C:\Users\sergey\AppData\Local\pypoetry\Cache\virtualenvs\aiohttp-example-zDtRzW9K-py3.11\Lib\site-packages\aiohttp\web.py", line 516, in run_app
    loop.run_until_complete(main_task)
  File "C:\Users\sergey\AppData\Local\Programs\Python\Python311\Lib\asyncio\base_events.py", line 653, in run_until_complete
    return future.result()
           ^^^^^^^^^^^^^^^
  File "C:\Users\sergey\AppData\Local\pypoetry\Cache\virtualenvs\aiohttp-example-zDtRzW9K-py3.11\Lib\site-packages\aiohttp\web.py", line 323, in _run_app
    await runner.setup()
  File "C:\Users\sergey\AppData\Local\pypoetry\Cache\virtualenvs\aiohttp-example-zDtRzW9K-py3.11\Lib\site-packages\aiohttp\web_runner.py", line 279, in setup
    self._server = await self._make_server()
                   ^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\sergey\AppData\Local\pypoetry\Cache\virtualenvs\aiohttp-example-zDtRzW9K-py3.11\Lib\site-packages\aiohttp\web_runner.py", line 375, in _make_server
    await self._app.startup()
  File "C:\Users\sergey\AppData\Local\pypoetry\Cache\virtualenvs\aiohttp-example-zDtRzW9K-py3.11\Lib\site-packages\aiohttp\web_app.py", line 417, in startup
    await self.on_startup.send(self)
  File "C:\Users\sergey\AppData\Local\pypoetry\Cache\virtualenvs\aiohttp-example-zDtRzW9K-py3.11\Lib\site-packages\aiosignal\__init__.py", line 36, in send
    await receiver(*args, **kwargs)  # type: ignore
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\sergey\AppData\Local\pypoetry\Cache\virtualenvs\aiohttp-example-zDtRzW9K-py3.11\Lib\site-packages\aiohttp\web_app.py", line 539, in _on_startup
    await it.__anext__()
  File "F:\python\AIOHTTP\polls\app_polls\db.py", line 32, in pg_context
    engine = await aiopg.sa.create_engine(
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\sergey\AppData\Local\pypoetry\Cache\virtualenvs\aiohttp-example-zDtRzW9K-py3.11\Lib\site-packages\aiopg\sa\engine.py", line 94, in _create_engine
    pool = await aiopg.create_pool(
           ^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\sergey\AppData\Local\pypoetry\Cache\virtualenvs\aiohttp-example-zDtRzW9K-py3.11\Lib\site-packages\aiopg\pool.py", line 300, in from_pool_fill
    await self._fill_free_pool(False)
  File "C:\Users\sergey\AppData\Local\pypoetry\Cache\virtualenvs\aiohttp-example-zDtRzW9K-py3.11\Lib\site-packages\aiopg\pool.py", line 336, in _fill_free_pool
    conn = await connect(
                 ^^^^^^^^
  File "C:\Users\sergey\AppData\Local\pypoetry\Cache\virtualenvs\aiohttp-example-zDtRzW9K-py3.11\Lib\site-packages\aiopg\connection.py", line 65, in connect
    connection = Connection(
                 ^^^^^^^^^^^
  File "C:\Users\sergey\AppData\Local\pypoetry\Cache\virtualenvs\aiohttp-example-zDtRzW9K-py3.11\Lib\site-packages\aiopg\connection.py", line 772, in __init__
    self._loop.add_reader(
  File "C:\Users\sergey\AppData\Local\Programs\Python\Python311\Lib\asyncio\events.py", line 530, in add_reader
    raise NotImplementedError
NotImplementedError
Traceback (most recent call last):
  File "F:\python\AIOHTTP\polls\app_polls\main.py", line 11, in <module>
    web.run_app(app)
  File "C:\Users\sergey\AppData\Local\pypoetry\Cache\virtualenvs\aiohttp-example-zDtRzW9K-py3.11\Lib\site-packages\aiohttp\web.py", line 516, in run_app
    loop.run_until_complete(main_task)
  File "C:\Users\sergey\AppData\Local\Programs\Python\Python311\Lib\asyncio\base_events.py", line 653, in run_until_complete
    return future.result()
           ^^^^^^^^^^^^^^^
  File "C:\Users\sergey\AppData\Local\pypoetry\Cache\virtualenvs\aiohttp-example-zDtRzW9K-py3.11\Lib\site-packages\aiohttp\web.py", line 323, in _run_app
    await runner.setup()
  File "C:\Users\sergey\AppData\Local\pypoetry\Cache\virtualenvs\aiohttp-example-zDtRzW9K-py3.11\Lib\site-packages\aiohttp\web_runner.py", line 279, in setup
    self._server = await self._make_server()
                   ^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\sergey\AppData\Local\pypoetry\Cache\virtualenvs\aiohttp-example-zDtRzW9K-py3.11\Lib\site-packages\aiohttp\web_runner.py", line 375, in _make_server
    await self._app.startup()
  File "C:\Users\sergey\AppData\Local\pypoetry\Cache\virtualenvs\aiohttp-example-zDtRzW9K-py3.11\Lib\site-packages\aiohttp\web_app.py", line 417, in startup
    await self.on_startup.send(self)
  File "C:\Users\sergey\AppData\Local\pypoetry\Cache\virtualenvs\aiohttp-example-zDtRzW9K-py3.11\Lib\site-packages\aiosignal\__init__.py", line 36, in send
    await receiver(*args, **kwargs)  # type: ignore
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\sergey\AppData\Local\pypoetry\Cache\virtualenvs\aiohttp-example-zDtRzW9K-py3.11\Lib\site-packages\aiohttp\web_app.py", line 539, in _on_startup
    await it.__anext__()
  File "F:\python\AIOHTTP\polls\app_polls\db.py", line 32, in pg_context
    engine = await aiopg.sa.create_engine(
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\sergey\AppData\Local\pypoetry\Cache\virtualenvs\aiohttp-example-zDtRzW9K-py3.11\Lib\site-packages\aiopg\sa\engine.py", line 94, in _create_engine
    pool = await aiopg.create_pool(
           ^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\sergey\AppData\Local\pypoetry\Cache\virtualenvs\aiohttp-example-zDtRzW9K-py3.11\Lib\site-packages\aiopg\pool.py", line 300, in from_pool_fill
    await self._fill_free_pool(False)
  File "C:\Users\sergey\AppData\Local\pypoetry\Cache\virtualenvs\aiohttp-example-zDtRzW9K-py3.11\Lib\site-packages\aiopg\pool.py", line 336, in _fill_free_pool
    conn = await connect(
                 ^^^^^^^^
  File "C:\Users\sergey\AppData\Local\pypoetry\Cache\virtualenvs\aiohttp-example-zDtRzW9K-py3.11\Lib\site-packages\aiopg\connection.py", line 65, in connect
    connection = Connection(
                 ^^^^^^^^^^^
  File "C:\Users\sergey\AppData\Local\pypoetry\Cache\virtualenvs\aiohttp-example-zDtRzW9K-py3.11\Lib\site-packages\aiopg\connection.py", line 772, in __init__
    self._loop.add_reader(
  File "C:\Users\sergey\AppData\Local\Programs\Python\Python311\Lib\asyncio\events.py", line 530, in add_reader
    raise NotImplementedError
NotImplementedError
Exception ignored in: <function Connection.__del__ at 0x000001CF28EEC360>
Traceback (most recent call last):
  File "C:\Users\sergey\AppData\Local\pypoetry\Cache\virtualenvs\aiohttp-example-zDtRzW9K-py3.11\Lib\site-packages\aiopg\connection.py", line 1188, in __del__
  File "C:\Users\sergey\AppData\Local\pypoetry\Cache\virtualenvs\aiohttp-example-zDtRzW9K-py3.11\Lib\site-packages\aiopg\connection.py", line 995, in close
  File "C:\Users\sergey\AppData\Local\pypoetry\Cache\virtualenvs\aiohttp-example-zDtRzW9K-py3.11\Lib\site-packages\aiopg\connection.py", line 977, in _close
  File "C:\Users\sergey\AppData\Local\Programs\Python\Python311\Lib\asyncio\events.py", line 533, in remove_reader
NotImplementedError:

[Dreamsorcerer]

I'd recommend just replacing aiopg with sqlalchemy 2. There's some in-progress work on updating the tutorials in aio-libs/aiohttp-demos#428
But, you may need to refer to the sqlalchemy documentation to figure it out correctly (I've not reviewed the changes yet, as tests are still failing).