Application startup fails

[dineshbvadhia]

The code looks like:

import anyio
from asapi import serve
from fastapi import FastAPI

app = FastAPI()

app.include_router(router)
add_exception_handler(
    app,
    logger=logger,
    )

async def main():
    do_startup_stuff()    
    await serve(app, 8000)

if __name__ == "__main__":
    anyio.run(main)    

The code excecutes do_startup_stuff() successfully but fails to start the fastapi app. The error trace is:

INFO:     Started server process [19096]
INFO:     Waiting for application startup.
ERROR:    Traceback (most recent call last):
  File "...asapi\_signal_handling.py", line 46, in handle_signals
    yield stop
  File "...asapi\_serve.py", line 21, in serve
    await stop.wait()
  File "...anyio\_backends\_asyncio.py", line 1662, in wait
    await self._event.wait()
  File "... asyncio\locks.py", line 213, in wait
    await fut
asyncio.exceptions.CancelledError: Cancelled by cancel scope 1df6aaa8690

The full traceback is longer and can post if required.

[adriangb]

I think it will be. This seems to be something going on inside of do_startup_stuff(). This example works without issues:

import anyio
from asapi import serve
from fastapi import FastAPI

app = FastAPI()

def do_startup_stuff():
    print('Doing startup stuff')

async def main():
    do_startup_stuff()
    await serve(app, 8000)

if __name__ == '__main__':
    anyio.run(main)

I don't know what your do_startup_stuff() is or what add_exception_handler is

[adriangb]

Could you try removing one at a time of do_startup_stuff and add_exception_handler and mounting the router to see which one is causing the issue?

[dineshbvadhia]

At startup the following happens: cli validation, db connection creation and read data which work as expected. The db connection (dao) forms the fastapi dependency DaoDep = Annotated[Dao, Depends(resolve_dao)] which has been replaced with asapi Injected. The asapi skeleton code structure is:

from fastapi import FastAPI
import anyio
from asapi import Injected, serve, bind

class Dao:
    ...

@app.get("/")
async def get(dao: Injected[Dao]):
    ...

app = FastAPI()

async def main():
    do_cli_validation()     # works
    dao = Dao()
    bind(app, Dao, dao)
    do_read_data(dao)       # works, so dao = Dao() works
    await serve(app, 8000)

if __name__ == "__main__":
    anyio.run(main)  

The startup error is as before. Is the Injected dependency not configured correctly?

The full traceback is:

INFO:     Started server process [6840]
INFO:     Waiting for application startup.

ERROR:    Traceback (most recent call last):
  asapi\_signal_handling.py", line 46, in handle_signals
    yield stop
  asapi\_serve.py", line 21, in serve
    await stop.wait()
  anyio\_backends\_asyncio.py", line 1662, in wait
    await self._event.wait()
  asyncio\locks.py", line 213, in wait
    await fut
asyncio.exceptions.CancelledError: Cancelled by cancel scope 1d3f7af3a50

During handling of the above exception, another exception occurred:

  + Exception Group Traceback (most recent call last):
  |   anyio\_backends\_asyncio.py", line 2034, in run
  |     return runner.run(wrapper())
  |            ^^^^^^^^^^^^^^^^^^^^^
  |   asyncio\runners.py", line 118, in run
  |     return self._loop.run_until_complete(task)
  |            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  |   asyncio\base_events.py", line 653, in run_until_complete
  |     return future.result()
  |            ^^^^^^^^^^^^^^^
  |   anyio\_backends\_asyncio.py", line 2022, in wrapper
  |     return await func(*args)
  |            ^^^^^^^^^^^^^^^^^
  |   server_asapi.py", line 613, in main
  |     await serve(app, 8000)
  |   asapi\_serve.py", line 18, in serve
  |     async with handle_signals() as stop:
  |   contextlib.py", line 222, in __aexit__
  |     await self.gen.athrow(typ, value, traceback)
  |   asapi\_signal_handling.py", line 44, in handle_signals
  |     async with anyio.create_task_group() as tg:
  |   anyio\_backends\_asyncio.py", line 680, in __aexit__
  |     raise BaseExceptionGroup(
  | ExceptionGroup: unhandled errors in a TaskGroup (1 sub-exception)
  +-+---------------- 1 ----------------
    | Traceback (most recent call last):
    |   asapi\_signal_handling.py", line 17, in _signal_handler
    |     with anyio.open_signal_receiver(signal.SIGTERM, signal.SIGINT) as signals:
    |   anyio\_backends\_asyncio.py", line 1805, in __enter__
    |     self._loop.add_signal_handler(sig, self._deliver, sig)
    |   asyncio\events.py", line 574, in add_signal_handler
    |     raise NotImplementedError
    | NotImplementedError
    +------------------------------------

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  starlette\routing.py", line 741, in lifespan
    await receive()
  uvicorn\lifespan\on.py", line 137, in receive
    return await self.receive_queue.get()
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  asyncio\queues.py", line 158, in get
    await getter
asyncio.exceptions.CancelledError

[dineshbvadhia]

from asapi import Injected, serve, bind, validate_injections

Generates the error:

Traceback (most recent call last):
  File "...server_asapi.py", line 71, in <module>
    from asapi import Injected, serve, bind, validate_injections
ImportError: cannot import name 'validate_injections' from 'asapi' (...asapi\__init__.py)

[adriangb]

Do you mean that literally just the imports generate that error for you?

from asapi import Injected, serve, bind, validate_injections

?

That seems very strange: https://github.com/adriangb/asapi/blob/e2ed763efa7c8e0f6c5383575e036484159390e5/asapi/__init__.py#L1

Has been like that since the initial commit.

[adriangb]

|   asapi\_signal_handling.py", line 17, in _signal_handler
|     with anyio.open_signal_receiver(signal.SIGTERM, signal.SIGINT) as signals:
|   anyio\_backends\_asyncio.py", line 1805, in __enter__
|     self._loop.add_signal_handler(sig, self._deliver, sig)
|   asyncio\events.py", line 574, in add_signal_handler
|     raise NotImplementedError

That's a very weird place to have that error. What event loop implementation are you using? Can you share your version of Python, anyio and asapi?

Thanks

[dineshbvadhia]

Yes

from asapi import Injected, serve, bind, validate_injections

Generates the error:

Traceback (most recent call last):
  File "...server_asapi.py", line 71, in <module>
    from asapi import Injected, serve, bind, validate_injections
ImportError: cannot import name 'validate_injections' from 'asapi' (...asapi\__init__.py)

Also, happens when importing from python interpreter ie.

> python
Python 3.11.4 (tags/v3.11.4:d2340ef, Jun  7 2023, 05:45:37) [MSC v.1934 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import asapi
>>> from asapi import Injected, serve, bind, validate_injections
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ImportError: cannot import name 'validate_injections' from 'asapi' (...asapi\__init__.py)

[dineshbvadhia]

Windows 11 Pro 23H2 w/ latest update python 3.11.4 anyio 4.4.0 asapi 0.1.2

[adriangb]

Ups I can reproduce! The wheel for asapi 0.1.2 was broken. I haven't really setup proper CI yet. Please try 0.1.3.

[dineshbvadhia]

from asapi import Injected, serve, bind, validate_injections

Solved with 0.1.3 :)

[dineshbvadhia]

But, the add_signal_handler (or other) remains ie.

Traceback (most recent call last):
  ...asapi\_signal_handling.py", line 48, in handle_signals
    yield stop
  ...asapi\_serve.py", line 21, in serve
    await stop.wait()
  ...anyio\_backends\_asyncio.py", line 1662, in wait
    await self._event.wait()
  ...asyncio\locks.py", line 213, in wait
    await fut
asyncio.exceptions.CancelledError: Cancelled by cancel scope 1ea4b2b9890

During handling of the above exception, another exception occurred:

  + Exception Group Traceback (most recent call last):
  |   ...server_asapi.py", line 585, in <module>
  |     anyio.run(main)
  |   ...anyio\_core\_eventloop.py", line 74, in run
  |     return async_backend.run(func, args, {}, backend_options)
  |            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  |   ...anyio\_backends\_asyncio.py", line 2034, in run
  |     return runner.run(wrapper())
  |            ^^^^^^^^^^^^^^^^^^^^^
  |   ...asyncio\runners.py", line 118, in run
  |     return self._loop.run_until_complete(task)
  |            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  |   ...asyncio\base_events.py", line 653, in run_until_complete
  |     return future.result()
  |            ^^^^^^^^^^^^^^^
  |   ...anyio\_backends\_asyncio.py", line 2022, in wrapper
  |     return await func(*args)
  |            ^^^^^^^^^^^^^^^^^
  |   ...server_asapi.py", line 581, in main
  |     await serve(app, 8000)
  |   ...asapi\_serve.py", line 18, in serve
  |     async with handle_signals() as stop:
  |   ...contextlib.py", line 222, in __aexit__
  |     await self.gen.athrow(typ, value, traceback)
  |   ...asapi\_signal_handling.py", line 46, in handle_signals
  |     async with anyio.create_task_group() as tg:
  |   ...anyio\_backends\_asyncio.py", line 680, in __aexit__
  |     raise BaseExceptionGroup(
  | ExceptionGroup: unhandled errors in a TaskGroup (1 sub-exception)
  +-+---------------- 1 ----------------
    | Traceback (most recent call last):
    |   ...asapi\_signal_handling.py", line 19, in _signal_handler
    |     with anyio.open_signal_receiver(signal.SIGTERM, signal.SIGINT) as signals:
    |   ...anyio\_backends\_asyncio.py", line 1805, in __enter__
    |     self._loop.add_signal_handler(sig, self._deliver, sig)
    |   ...asyncio\events.py", line 574, in add_signal_handler
    |     raise NotImplementedError
    | NotImplementedError
    +------------------------------------

[adriangb]

I feel like you might be hitting https://github.com/python/cpython/blob/1b0e63c81b54a937b089fe335761cba4a96c8cdf/Lib/asyncio/events.py#L578, which doesn't make much sense. I'll look deeper tomorrow hopefully.

[dineshbvadhia]

Thanks. In your time.

Fyi I'm testing asapi with my full system which works using the fastapi Annotated() dependency except for the cli problem which is related to uvicorn. Happy to be a guinea pig for asapi :)

[adriangb]

I now set up CI including Windows and added a test that passes.

I'm guessing you're hitting this line? https://github.com/python/cpython/blob/1b0e63c81b54a937b089fe335761cba4a96c8cdf/Lib/asyncio/events.py#L578 Could you share a couple lines above 574 and below in asyncio/events.py to confirm?

Also could you check if this snippet works for you?

import signal
import anyio

async def main() -> None:
    with anyio.open_signal_receiver(signal.SIGTERM, signal.SIGINT) as signals:
        async for sig in signals:
            print(f'Received signal {sig!r}')

anyio.run(main)

Thanks!

[dineshbvadhia]

asapi 0.1.3

The problem is at this line : https://github.com/python/cpython/blob/1b0e63c81b54a937b089fe335761cba4a96c8cdf/Lib/asyncio/events.py#L578

See the Traceback above https://github.com/adriangb/asapi/issues/2#issuecomment-2171690585

Don't understand what 'Could you share a couple lines above 574 and below in asyncio/events.py to confirm?' means?

The above snippet generated the Traceback:

Traceback (most recent call last):
  ...snippet.py", line 11, in <module>
    anyio.run(main)
  ...anyio\_core\_eventloop.py", line 74, in run
    return async_backend.run(func, args, {}, backend_options)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  ...anyio\_backends\_asyncio.py", line 2034, in run
    return runner.run(wrapper())
           ^^^^^^^^^^^^^^^^^^^^^
  ...asyncio\runners.py", line 118, in run
    return self._loop.run_until_complete(task)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  ...asyncio\base_events.py", line 653, in run_until_complete
    return future.result()
           ^^^^^^^^^^^^^^^
  ...anyio\_backends\_asyncio.py", line 2022, in wrapper
    return await func(*args)
           ^^^^^^^^^^^^^^^^^
  ...snippet.py", line 6, in main
    with anyio.open_signal_receiver(signal.SIGTERM, signal.SIGINT) as signals:
  ...anyio\_backends\_asyncio.py", line 1805, in __enter__
    self._loop.add_signal_handler(sig, self._deliver, sig)
  ...asyncio\events.py", line 574, in add_signal_handler
    raise NotImplementedError
NotImplementedError

[adriangb]

I just wanted to confirm what line that error is coming from. Can you let me know what happens with the snippet in https://github.com/adriangb/asapi/issues/2#issuecomment-2181634297?

[dineshbvadhia]

The snippet:

import signal
import anyio

async def main() -> None:
    with anyio.open_signal_receiver(signal.SIGTERM, signal.SIGINT) as signals:
        async for sig in signals:
            print(f'Received signal {sig!r}')

anyio.run(main)

Generates the Traceback:

Traceback (most recent call last):
  ...snippet.py", line 11, in <module>
    anyio.run(main)
  ...anyio\_core\_eventloop.py", line 74, in run
    return async_backend.run(func, args, {}, backend_options)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  ...anyio\_backends\_asyncio.py", line 2034, in run
    return runner.run(wrapper())
           ^^^^^^^^^^^^^^^^^^^^^
  ...asyncio\runners.py", line 118, in run
    return self._loop.run_until_complete(task)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  ...asyncio\base_events.py", line 653, in run_until_complete
    return future.result()
           ^^^^^^^^^^^^^^^
  ...anyio\_backends\_asyncio.py", line 2022, in wrapper
    return await func(*args)
           ^^^^^^^^^^^^^^^^^
  ...snippet.py", line 6, in main
    with anyio.open_signal_receiver(signal.SIGTERM, signal.SIGINT) as signals:
  ...anyio\_backends\_asyncio.py", line 1805, in __enter__
    self._loop.add_signal_handler(sig, self._deliver, sig)
  ...asyncio\events.py", line 574, in add_signal_handler
    raise NotImplementedError
NotImplementedError

[adriangb]

I think it may be that (some?) flavors of Windows don't support SIGTERM. Can you try removing SIGTERM?

Thank you for helping me debug, I don't have a Windows machine so I can't really test these things.

[dineshbvadhia]

Happy to help :)

Removing SIGTERM ie.

import signal
import anyio

async def main() -> None:
    with anyio.open_signal_receiver(signal.SIGINT) as signals:
        async for sig in signals:
            print(f'Received signal {sig!r}')

anyio.run(main)

Generates the Traceback:

Traceback (most recent call last):
  ...snippet.py", line 9, in <module>
    anyio.run(main)
  ...anyio\_core\_eventloop.py", line 74, in run
    return async_backend.run(func, args, {}, backend_options)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  ...anyio\_backends\_asyncio.py", line 2034, in run
    return runner.run(wrapper())
           ^^^^^^^^^^^^^^^^^^^^^
  ...asyncio\runners.py", line 118, in run
    return self._loop.run_until_complete(task)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  ...asyncio\base_events.py", line 653, in run_until_complete
    return future.result()
           ^^^^^^^^^^^^^^^
  ...anyio\_backends\_asyncio.py", line 2022, in wrapper
    return await func(*args)
           ^^^^^^^^^^^^^^^^^
  ...snippet.py", line 5, in main
    with anyio.open_signal_receiver(signal.SIGINT) as signals:
  ...anyio\_backends\_asyncio.py", line 1805, in __enter__
    self._loop.add_signal_handler(sig, self._deliver, sig)
  ...asyncio\events.py", line 574, in add_signal_handler
    raise NotImplementedError
NotImplementedError

[dineshbvadhia]

At the anyio open_signal_receiverfunction https://github.com/agronholm/anyio/blob/e93d5c9157ad045f1f9dffbcbba6d005febdb9e9/src/anyio/_core/_signals.py#L10 it says:

warning:: Windows does not support signals natively so it is best to avoid
        relying on this in cross-platform applications.

Maybe setting the asyncio WindowsSelectorEventLoopPolicy is an option to try: https://docs.python.org/3.11/library/asyncio-policy.html#asyncio.WindowsSelectorEventLoopPolicy for Windows ('win*')

asyncio.set_event_loop_policy(asyncio.WindowsSelectorEventLoopPolicy())

[adriangb]

I’ll probably have to look at what Uvicorn does on Windows and just copy that.

On Sat, Jun 22, 2024 at 1:13 PM Henry Thornton @.***> wrote:

At the anyio open_signal_receiver function https://github.com/agronholm/anyio/blob/e93d5c9157ad045f1f9dffbcbba6d005febdb9e9/src/anyio/_core/_signals.py#L10 it says:

warning:: Windows does not support signals natively so it is best to avoid relying on this in cross-platform applications.

Maybe setting the asyncio WindowsSelectorEventLoopPolicy is an option to try: https://docs.python.org/3.11/library/asyncio-policy.html#asyncio.WindowsSelectorEventLoopPolicy for Windows ('win*')

asyncio.set_event_loop_policy(asyncio.WindowsSelectorEventLoopPolicy())

— Reply to this email directly, view it on GitHub https://github.com/adriangb/asapi/issues/2#issuecomment-2184136418, or unsubscribe https://github.com/notifications/unsubscribe-auth/AANMPP72P32BOUBRG6K66G3ZIW5FLAVCNFSM6AAAAABJISYRJKVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZDCOBUGEZTMNBRHA . You are receiving this because you commented.Message ID: @.***>

[dineshbvadhia]

Saw this on the uvicorn site: https://github.com/encode/uvicorn/blob/d79f285184404694c77f7ca649858e7488270cf7/uvicorn/loops/asyncio.py

[dineshbvadhia]

Hi Wondering if you've had a chance to work on this? Thanks