Added logging for startup failures

[mingregister]

Scene

We deploy our Uvicorn app in Kubernetes, and we send our logs to the Aliyun log service. However, we've noticed that when the startup fails (e.g: due to a forgotten module import), the error logs are not visible in the Aliyun log service. As a result:

1. We are forced to log into the Kubernetes node to determine what happened.
2. Furthermore, when the startup fails, the Kubernetes pod is restarted, leading to the loss of logs, which increases the difficulty of troubleshooting.

So, Should we added logging for startup failures?

Code and Traceback

from fastapi import FastAPI
import uvicorn

# import os  # suppose we forgot to import os module, which will cause promgramer startup failed
foo_bar = os.getenv("ENV_FOO_BAR")  

app = FastAPI(description=foo_bar)

@app.get("/hello")
async def hello():
    return {"message": "Hello World"}

Then, use the command uvicorn main:app --log-config uvicore_config.json to start up. If it fails to start, the traceback is as follows:

Due to the reasons mentioned above, we cannot see the errors in the aliyun log service; we must log in to Kubernetes to view them.

Traceback (most recent call last):
  File "/home/code/opsv2/.venv/bin/uvicorn", line 8, in <module>
    sys.exit(main())
             ^^^^^^
  File "/home/code/opsv2/.venv/lib/python3.12/site-packages/click/core.py", line 1157, in __call__
    return self.main(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/code/opsv2/.venv/lib/python3.12/site-packages/click/core.py", line 1078, in main
    rv = self.invoke(ctx)
         ^^^^^^^^^^^^^^^^
  File "/home/code/opsv2/.venv/lib/python3.12/site-packages/click/core.py", line 1434, in invoke
    return ctx.invoke(self.callback, **ctx.params)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/code/opsv2/.venv/lib/python3.12/site-packages/click/core.py", line 783, in invoke
    return __callback(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/code/uvicorn/uvicorn/main.py", line 410, in main
    run(
  File "/home/code/uvicorn/uvicorn/main.py", line 577, in run
    server.run()
  File "/home/code/uvicorn/uvicorn/server.py", line 71, in run
    raise e
  File "/home/code/uvicorn/uvicorn/server.py", line 67, in run
    return asyncio.run(self.serve(sockets=sockets))
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/python3.12.2/lib/python3.12/asyncio/runners.py", line 194, in run
    return runner.run(main)
           ^^^^^^^^^^^^^^^^
  File "/usr/local/python3.12.2/lib/python3.12/asyncio/runners.py", line 118, in run
    return self._loop.run_until_complete(task)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "uvloop/loop.pyx", line 1517, in uvloop.loop.Loop.run_until_complete
  File "/home/code/uvicorn/uvicorn/server.py", line 75, in serve
    await self._serve(sockets)
  File "/home/code/uvicorn/uvicorn/server.py", line 82, in _serve
    config.load()
  File "/home/code/uvicorn/uvicorn/config.py", line 434, in load
    self.loaded_app = import_from_string(self.app)
                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/code/uvicorn/uvicorn/importer.py", line 19, in import_from_string
    module = importlib.import_module(module_str)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/python3.12.2/lib/python3.12/importlib/__init__.py", line 90, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "<frozen importlib._bootstrap>", line 1387, in _gcd_import
  File "<frozen importlib._bootstrap>", line 1360, in _find_and_load
  File "<frozen importlib._bootstrap>", line 1331, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 935, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 995, in exec_module
  File "<frozen importlib._bootstrap>", line 488, in _call_with_frames_removed
  File "/home/code/opsv2/app/main.py", line 7, in <module>
    foo_bar = os.getenv("ENV_FOO_BAR")
              ^^
NameError: name 'os' is not defined. Did you forget to import 'os'?

Solution

I've proposed a solution that can be found at this PR. I understand that it may not be the final approach we take, but I welcome your insights and suggestions.