Reload=False causes errors on Windows 10

[msminhas93]

I have been trying to use uvicorn on Windows 10 with reload=False i.e. production setting. However, I get Accept failed on a socket error on all the threads.

My OS is: Windows 10 Version 1909 (OS Build 18363.2158)

My conda environment is created using the following yml file:

name: windows-service
channels:
  - pytorch
  - conda-forge
  - defaults
dependencies:
  - fastapi=0.74.0
  - pyinstaller=4.9
  - python=3.9.10
  - uvicorn=0.17.5
  - requests=2.27.1
  - psutil=5.9.0
  - webencodings
  - pip=22.0.4

Error Dump:

INFO:     Uvicorn running on http://127.0.0.1:5000 (Press CTRL+C to quit)
INFO:     Started parent process [86244]
INFO:     Started server process [83988]
INFO:     Waiting for application startup.
INFO:     Application startup complete.   
INFO:     Started server process [14976]
INFO:     Waiting for application startup.       
INFO:     Application startup complete.
INFO:     Started server process [66784]
INFO:     Waiting for application startup.       
INFO:     Application startup complete.
INFO:     Started server process [17572]
INFO:     Waiting for application startup.
INFO:     Application startup complete.
INFO:     Started server process [59164]
INFO:     Waiting for application startup.
INFO:     Application startup complete.
INFO:     Started server process [61760]
INFO:     Waiting for application startup.
INFO:     Started server process [37712]
INFO:     Waiting for application startup.
INFO:     Application startup complete.
INFO:     Application startup complete.
INFO:     Started server process [90404]
INFO:     Waiting for application startup.
INFO:     Application startup complete.
INFO:     Started server process [36860]
INFO:     Waiting for application startup.
INFO:     Application startup complete.
Accept failed on a socket
socket: <asyncio.TransportSocket fd=516, family=AddressFamily.AF_INET, type=SocketKind.SOCK_STREAM, proto=6, laddr=('127.0.0.1', 5000)>
Traceback (most recent call last):
  File "C:\Users\m.minhas\Miniconda3\envs\mlserveronnx\lib\asyncio\proactor_events.py", line 834, in loop
    f = self._proactor.accept(sock)
  File "C:\Users\m.minhas\Miniconda3\envs\mlserveronnx\lib\asyncio\windows_events.py", line 554, in accept
    self._register_with_iocp(listener)
  File "C:\Users\m.minhas\Miniconda3\envs\mlserveronnx\lib\asyncio\windows_events.py", line 723, in _register_with_iocp
    _overlapped.CreateIoCompletionPort(obj.fileno(), self._iocp, 0, 0)
OSError: [WinError 87] The parameter is incorrect
Accept failed on a socket
socket: <asyncio.TransportSocket fd=532, family=AddressFamily.AF_INET, type=SocketKind.SOCK_STREAM, proto=6, laddr=('127.0.0.1', 5000)>
Traceback (most recent call last):
  File "C:\Users\m.minhas\Miniconda3\envs\mlserveronnx\lib\asyncio\proactor_events.py", line 834, in loop
    f = self._proactor.accept(sock)
  File "C:\Users\m.minhas\Miniconda3\envs\mlserveronnx\lib\asyncio\windows_events.py", line 554, in accept
    self._register_with_iocp(listener)
  File "C:\Users\m.minhas\Miniconda3\envs\mlserveronnx\lib\asyncio\windows_events.py", line 723, in _register_with_iocp
    _overlapped.CreateIoCompletionPort(obj.fileno(), self._iocp, 0, 0)
OSError: [WinError 87] The parameter is incorrect
Accept failed on a socket
socket: <asyncio.TransportSocket fd=844, family=AddressFamily.AF_INET, type=SocketKind.SOCK_STREAM, proto=6, laddr=('127.0.0.1', 5000)>
Traceback (most recent call last):
  File "C:\Users\m.minhas\Miniconda3\envs\mlserveronnx\lib\asyncio\proactor_events.py", line 834, in loop
    f = self._proactor.accept(sock)
  File "C:\Users\m.minhas\Miniconda3\envs\mlserveronnx\lib\asyncio\windows_events.py", line 554, in accept
    self._register_with_iocp(listener)
  File "C:\Users\m.minhas\Miniconda3\envs\mlserveronnx\lib\asyncio\windows_events.py", line 723, in _register_with_iocp
    _overlapped.CreateIoCompletionPort(obj.fileno(), self._iocp, 0, 0)
OSError: [WinError 87] The parameter is incorrect
Accept failed on a socket
socket: <asyncio.TransportSocket fd=952, family=AddressFamily.AF_INET, type=SocketKind.SOCK_STREAM, proto=6, laddr=('127.0.0.1', 5000)>
Traceback (most recent call last):
  File "C:\Users\m.minhas\Miniconda3\envs\mlserveronnx\lib\asyncio\proactor_events.py", line 834, in loop
    f = self._proactor.accept(sock)
  File "C:\Users\m.minhas\Miniconda3\envs\mlserveronnx\lib\asyncio\windows_events.py", line 554, in accept
    self._register_with_iocp(listener)
  File "C:\Users\m.minhas\Miniconda3\envs\mlserveronnx\lib\asyncio\windows_events.py", line 723, in _register_with_iocp
    _overlapped.CreateIoCompletionPort(obj.fileno(), self._iocp, 0, 0)
OSError: [WinError 87] The parameter is incorrect
Accept failed on a socket
socket: <asyncio.TransportSocket fd=964, family=AddressFamily.AF_INET, type=SocketKind.SOCK_STREAM, proto=6, laddr=('127.0.0.1', 5000)>
Traceback (most recent call last):
  File "C:\Users\m.minhas\Miniconda3\envs\mlserveronnx\lib\asyncio\proactor_events.py", line 834, in loop
    f = self._proactor.accept(sock)
  File "C:\Users\m.minhas\Miniconda3\envs\mlserveronnx\lib\asyncio\windows_events.py", line 554, in accept
    self._register_with_iocp(listener)
  File "C:\Users\m.minhas\Miniconda3\envs\mlserveronnx\lib\asyncio\windows_events.py", line 723, in _register_with_iocp
    _overlapped.CreateIoCompletionPort(obj.fileno(), self._iocp, 0, 0)
OSError: [WinError 87] The parameter is incorrect
Accept failed on a socket
socket: <asyncio.TransportSocket fd=460, family=AddressFamily.AF_INET, type=SocketKind.SOCK_STREAM, proto=6, laddr=('127.0.0.1', 5000)>
Traceback (most recent call last):
  File "C:\Users\m.minhas\Miniconda3\envs\mlserveronnx\lib\asyncio\proactor_events.py", line 834, in loop
    f = self._proactor.accept(sock)
  File "C:\Users\m.minhas\Miniconda3\envs\mlserveronnx\lib\asyncio\windows_events.py", line 554, in accept
    self._register_with_iocp(listener)
  File "C:\Users\m.minhas\Miniconda3\envs\mlserveronnx\lib\asyncio\windows_events.py", line 723, in _register_with_iocp
    _overlapped.CreateIoCompletionPort(obj.fileno(), self._iocp, 0, 0)
OSError: [WinError 87] The parameter is incorrect
Accept failed on a socket
socket: <asyncio.TransportSocket fd=932, family=AddressFamily.AF_INET, type=SocketKind.SOCK_STREAM, proto=6, laddr=('127.0.0.1', 5000)>
Traceback (most recent call last):
  File "C:\Users\m.minhas\Miniconda3\envs\mlserveronnx\lib\asyncio\proactor_events.py", line 834, in loop
    f = self._proactor.accept(sock)
  File "C:\Users\m.minhas\Miniconda3\envs\mlserveronnx\lib\asyncio\windows_events.py", line 554, in accept
    self._register_with_iocp(listener)
  File "C:\Users\m.minhas\Miniconda3\envs\mlserveronnx\lib\asyncio\windows_events.py", line 723, in _register_with_iocp
    _overlapped.CreateIoCompletionPort(obj.fileno(), self._iocp, 0, 0)
OSError: [WinError 87] The parameter is incorrect
Accept failed on a socket
socket: <asyncio.TransportSocket fd=836, family=AddressFamily.AF_INET, type=SocketKind.SOCK_STREAM, proto=6, laddr=('127.0.0.1', 5000)>
Traceback (most recent call last):
  File "C:\Users\m.minhas\Miniconda3\envs\mlserveronnx\lib\asyncio\proactor_events.py", line 834, in loop
    f = self._proactor.accept(sock)
  File "C:\Users\m.minhas\Miniconda3\envs\mlserveronnx\lib\asyncio\windows_events.py", line 554, in accept
    self._register_with_iocp(listener)
  File "C:\Users\m.minhas\Miniconda3\envs\mlserveronnx\lib\asyncio\windows_events.py", line 723, in _register_with_iocp
    _overlapped.CreateIoCompletionPort(obj.fileno(), self._iocp, 0, 0)
OSError: [WinError 87] The parameter is incorrect

I'm using a very basic sample from FastAPI:

from fastapi import FastAPI

app = FastAPI()


@app.get("/api/v1.0/check-status")
async def root():
    return {"Alive": True}

Uvicorn script:

import uvicorn
from multiprocessing import cpu_count, freeze_support


def start_server(host="127.0.0.1",
                 port=5000,
                 num_workers=4,
                 loop="asyncio",
                 reload=False):
    print(f"Starting the ML web server with {num_workers} workers.")
    uvicorn.run("web_server:app",
                host=host,
                port=port,
                workers=num_workers,
                loop=loop,
                reload=reload)
    print("Stopping the ML web server.")


if __name__ == "__main__":
    freeze_support()  # Needed for pyinstaller for multiprocessing on WindowsOS
    num_workers = int(cpu_count() * 0.75)
    start_server(num_workers=num_workers)

The servers work fine but I want to know why am I getting these errors and is there a way to not get those?

[Kludex]

This was fixed on uvicorn 0.18.0 - #1454.