Colab Enterprise unable to run FastAPI uvicorn (RuntimeWarning: coroutine 'Server.serve' was never awaited)

[gogasca]

I'm using Colab Enterprise and run the following code:

!pip install uvicorn[standard] fastapi

from fastapi import FastAPI
from fastapi.responses import PlainTextResponse

app = FastAPI()

app.get("/")
def greet():
  return PlainTextResponse("Hello")

import uvicorn
import threading

def run():
   uvicorn.run(app, port=7860)

t = threading.Thread(target=run)
t.start()

Running this code via a Notebook

Exception in thread Thread-10 (run):
Traceback (most recent call last):
  File "/usr/lib/python3.10/threading.py", line 1016, in _bootstrap_inner
    self.run()
  File "/usr/lib/python3.10/threading.py", line 953, in run
    self._target(*self._args, **self._kwargs)
  File "<ipython-input-3-45b7c0af2e07>", line 5, in run
  File "/usr/local/lib/python3.10/dist-packages/uvicorn/main.py", line 575, in run
    server.run()
  File "/usr/local/lib/python3.10/dist-packages/uvicorn/server.py", line 66, in run
    return asyncio.run(self.serve(sockets=sockets))
  File "/usr/local/lib/python3.10/dist-packages/nest_asyncio.py", line 26, in run
    loop = asyncio.get_event_loop()
  File "/usr/local/lib/python3.10/dist-packages/nest_asyncio.py", line 40, in _get_event_loop
    loop = events.get_event_loop_policy().get_event_loop()
  File "/usr/lib/python3.10/asyncio/events.py", line 656, in get_event_loop
    raise RuntimeError('There is no current event loop in thread %r.'
RuntimeError: There is no current event loop in thread 'Thread-10 (run)'.
setup_event_loop
uvicorn.loops.auto:auto_loop_setup
loop_setup is not None
None
/usr/lib/python3.10/threading.py:1018: RuntimeWarning: coroutine 'Server.serve' was never awaited
  self._invoke_excepthook(self)
RuntimeWarning: Enable tracemalloc to get the object allocation traceback

Note: I added some debugs to understand setup_event_loop logic.

python -m uvicorn --version
Running uvicorn 0.29.0 with CPython 3.10.12 on Linux

Colab Enterprise requirements.txt
Free Colab requirements.txt
Diff https://www.diffchecker.com/1AMpoTuM/

This works fine via free Colab.

Troubleshooting done:

• Uninstall nest-asyncio
• Tested in free Colab
• Use free Colab container in Colab Enterprise and the code works (No Exception). I try to install the diff libraries, and I can't reproduce.

Why uninstalling nest-asyncio is not an option? The same library is installed in free Colab.

Original issue: gradio-app/gradio#8238 (comment)

What other information I can use to debug this issue?

[gogasca]

This works fine in Colab Enterprise, but still want to understand the root cause and potential solution.

from fastapi import FastAPI
from fastapi.responses import PlainTextResponse
import uvicorn

app = FastAPI()

@app.get("/")
def greet():
    return PlainTextResponse("Hello")

def run():
   uvicorn.run(app, host="0.0.0.0", port=7860)

run()

[gogasca]

We are preloading an ipython extension (Via c.InteractiveShellApp.extensions) which is running nest_asyncio.apply() https://github.com/malloydata/malloy-py/blob/abe7d216512ed0d2b550a90658fa79deeba9f5b1/src/malloy/ipython/ipython_magic.py#L50