How to handle exceptions

[wackazong]

I have a fastapi example running with your library, I like the clean architecture. However, what is the best way to handle exceptions during dependency resolution? At the moment my FastAPI hangs and does not even return a 500.

[rmk135]

Could you, please, attach a code sample?

[rmk135]

Also could you, please, check the version of dependency injector: pip list | grep dependency-injector?

[wackazong]

I use poetry, dependency-injector is installed with 4.27.0. Here is my terminal output after doing a GET request to http://127.0.0.1:8000/listener/. The exception that I raise for testing is raised. I would expect that dependency-injector passes this exception to fastapi and fastapi handles it, resulting an a 500 being returned. Instead the request hangs.

% poetry run uvicorn api.main:app
INFO:     Started server process [22833]
INFO:     Waiting for application startup.
INFO:     Application startup complete.
INFO:     Uvicorn running on http://127.0.0.1:8000 (Press CTRL+C to quit)
Exception in callback Dependency._async_provide(<Future pendi...tasks.py:758]>)(<Future finis...n=Exception()>)
handle: <Handle Dependency._async_provide(<Future pendi...tasks.py:758]>)(<Future finis...n=Exception()>)>
Traceback (most recent call last):
  File "/usr/local/Cellar/python@3.8/3.8.5/Frameworks/Python.framework/Versions/3.8/lib/python3.8/asyncio/events.py", line 81, in _run
    self._context.run(self._callback, *self._args)
  File "src/dependency_injector/providers.pyx", line 767, in dependency_injector.providers.Dependency._async_provide
  File "src/dependency_injector/providers.pyx", line 2652, in dependency_injector.providers.BaseSingleton._async_init_instance
  File "src/dependency_injector/providers.pxd", line 566, in dependency_injector.providers.__async_call_callback
  File "src/dependency_injector/providers.pxd", line 458, in dependency_injector.providers.__async_prepare_args_kwargs_callback
  File "src/dependency_injector/providers.pyx", line 3489, in dependency_injector.providers.Resource._async_init_callback
  File "./api/gateways/redis.py", line 6, in init_redis
    raise Exception
Exception

I put together a simple test case here: https://github.com/wackazong/dependency-injector_exception_handling_test_case. Many thanks for your support!

[rmk135]

Thank you for the traceback and test case. There were similar issues in asynchronous mode before. I thought I fixed all of them in 4.23.2 and 4.23.3, but looks like there are still some issues. I'll take a look and get back to you.

[rmk135]

@wackazong Fixed in 4.28.1. Thanks for reporting the issue and providing the test case.

[wackazong]

Very cool. Thank you too.

[robmoore]

I believe I'm running into this issue. I have a Resource that calls an async init function. The function raises an exception and my app hangs indefinitely. I can create a separate ticket for this issue if desired but it seems to be similar to what @wackazong mentioned. I'm running with version 4.40.0.

[robmoore]

@rmk135 I can provide an example if that helps.