单文件运行Quart与Discord Bot双事件循环的Uvicorn异常问题

我开发了一个包含两个事件循环的Web应用：一个基于Quart微框架的Web应用，一个Discord机器人。为运行双事件循环，我给Discord机器人开了独立线程。用Python解释器直接运行正常，但通过Uvicorn启动Quart时抛出异常。相关代码和报错信息如下：

应用代码（Application.py） #

# Application.py
 
import os
import sys
import quart
from quart_discord import DiscordOAuth2Session
from Database import InformationLogManager
from Bot import Main
import threading
import asyncio
import typelog
 
os.environ['OAUTHLIB_INSECURE_TRANSPORT'] = '1'
 
GUILD_ID = 1208428835960520734
ROLE_ID = 1208433206215315558
 
Application = quart.Quart('888KingBotDashboard')
InformationLogManager = InformationLogManager.InformationLogManager() # 数据库实例
Logger = typelog.get_logger(__name__)
 
Application.config["SECRET_KEY"] = "thebigchickens"
Application.config["DISCORD_CLIENT_ID"] = '1208431980954525746'
Application.config["DISCORD_CLIENT_SECRET"] = 'ghvM9A2128vrz9vEzXrvOxp1ff28FIEC'
Application.config["DISCORD_REDIRECT_URI"] = "http://localhost:8080/callback"
 
DiscordOAuth2Session = DiscordOAuth2Session(Application)
 
@Application.before_serving
async def BeforeFirstRequest():
    BotThread = threading.Thread(target=Main.RunBot) # 启动Discord机器人
    BotThread.start()
 
@Application.route('/')
async def index():
    return await quart.render_template('index.html')
 
@Application.route('/login')
async def Login():
    return await DiscordOAuth2Session.create_session()
 
@Application.route('/callback')
async def callback():
    try:
        await DiscordOAuth2Session.callback()
    except Exception:
        return quart.redirect(quart.url_for("login"))
 
    User = await DiscordOAuth2Session.fetch_user()
    print(User)
    return await quart.render_template('logged_in_success.html', User = User)
 
@Application.route('/dashboard')
async def dashboard():
    for Guild in await DiscordOAuth2Session.fetch_guilds():
        if Guild.id == GUILD_ID:
            User = await DiscordOAuth2Session.fetch_user()
            if await Main.CheckForRole(GuildId = GUILD_ID, RoleId = ROLE_ID, UserId = User.id):
                InformationLogManager.LogInformation(
                    DiscordUserId = User.id,
                    IPAddress = quart.request.remote_addr,
                    Email = User.email
                )
                return await quart.render_template("dashboard.html", User = User)
            else:
                break
        else:
            continue
    return await quart.render_template("access_denied.html"), 401

报错信息 #

Exception in thread Thread-1 (RunBot):
Traceback (most recent call last):
  File "C:\Users\junej\dev\888BotRestructure\venv\lib\site-packages\disnake\client.py", line 1116, in run
Exception in callback Future.set_result(True)
handle: <TimerHandle when=527018.265 Future.set_result(True)>
Traceback (most recent call last):
  File "C:\Users\junej\AppData\Local\Programs\Python\Python310\lib\asyncio\events.py", line 80, in _run
    self._context.run(self._callback, *self._args)
asyncio.exceptions.InvalidStateError: invalid state
    loop.run_forever()
  File "C:\Users\junej\AppData\Local\Programs\Python\Python310\lib\asyncio\windows_events.py", line 319, in run_forever
INFO:     ASGI 'lifespan' protocol appears unsupported.
    assert self._self_reading_future is None
AssertionError
 
During handling of the above exception, another exception occurred:
 
Traceback (most recent call last):
  File "C:\Users\junej\dev\888BotRestructure\venv\lib\site-packages\disnake\client.py", line 133, in _cleanup_loop
    _cancel_tasks(loop)
  File "C:\Users\junej\dev\888BotRestructure\venv\lib\site-packages\disnake\client.py", line 115, in _cancel_tasks
    loop.run_until_complete(asyncio.gather(*tasks, return_exceptions=True))
  File "C:\Users\junej\AppData\Local\Programs\Python\Python310\lib\asyncio\base_events.py", line 617, in run_until_complete
    self._check_running()
  File "C:\Users\junej\AppData\Local\Programs\Python\Python310\lib\asyncio\base_events.py", line 577, in _check_running
asyncio.exceptions.CancelledError
 
During handling of the above exception, another exception occurred:
 
Traceback (most recent call last):
  File "C:\Users\junej\dev\888BotRestructure\venv\lib\site-packages\uvicorn\server.py", line 79, in serve
    await self.startup(sockets=sockets)
  File "C:\Users\junej\dev\888BotRestructure\venv\lib\site-packages\uvicorn\server.py", line 161, in startup
    server = await loop.create_server(
  File "C:\Users\junej\AppData\Local\Programs\Python\Python310\lib\asyncio\base_events.py", line 1459, in create_server
    infos = await tasks.gather(*fs)
asyncio.exceptions.CancelledError
 
During handling of the above exception, another exception occurred:
 
Traceback (most recent call last):
  File "C:\Users\junej\AppData\Local\Programs\Python\Python310\lib\runpy.py", line 196, in _run_module_as_main
    return _run_code(code, main_globals, None,
  File "C:\Users\junej\AppData\Local\Programs\Python\Python310\lib\runpy.py", line 86, in _run_code
    exec(code, run_globals)
  File "C:\Users\junej\dev\888BotRestructure\venv\Scripts\uvicorn.exe\__main__.py", line 7, in <module>
    sys.exit(main())
  File "C:\Users\junej\dev\888BotRestructure\venv\lib\site-packages\click\core.py", line 1157, in __call__
    return self.main(*args, **kwargs)
  File "C:\Users\junej\dev\888BotRestructure\venv\lib\site-packages\click\core.py", line 1078, in main
    rv = self.invoke(ctx)
  File "C:\Users\junej\dev\888BotRestructure\venv\lib\site-packages\click\core.py", line 1434, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "C:\Users\junej\dev\888BotRestructure\venv\lib\site-packages\click\core.py", line 783, in invoke
    return __callback(*args, **kwargs)
  File "C:\Users\junej\dev\888BotRestructure\venv\lib\site-packages\uvicorn\main.py", line 418, in main
    run(
  File "C:\Users\junej\dev\888BotRestructure\venv\lib\site-packages\uvicorn\main.py", line 587, in run
    server.run()
  File "C:\Users\junej\dev\888BotRestructure\venv\lib\site-packages\uvicorn\server.py", line 62, in run
    Client.run("MTIwODQzMTk4MDk1NDUyNTc0Ng.GJL1Ys.WJk760ouaguhQ818OJMu8z9GvKDOzFAA0pBxuk")
  File "C:\Users\junej\dev\888BotRestructure\venv\lib\site-packages\disnake\client.py", line 1122, in run
    _cleanup_loop(loop)
  File "C:\Users\junej\dev\888BotRestructure\venv\lib\site-packages\disnake\client.py", line 137, in _cleanup_loop
    loop.close()
  File "C:\Users\junej\AppData\Local\Programs\Python\Python310\lib\asyncio\proactor_events.py", line 676, in close
    raise RuntimeError("Cannot close a running event loop")
RuntimeError: Cannot close a running event loop

问题核心是多线程下asyncio事件循环的资源冲突。Uvicorn启动时会创建并严格管理自己的事件循环，而子线程中调用的client.run()会尝试创建独立事件循环，但Windows环境的ProactorEventLoop不支持这种多线程启动模式，且机器人的自动清理逻辑会和Uvicorn的主循环产生冲突。

具体修复步骤： #

1. 重构Discord机器人的启动逻辑
   不要使用client.run()，而是手动为子线程创建独立事件循环，用loop.run_until_complete(client.start(token))启动机器人。修改Bot.py中的Main.RunBot函数：

   import asyncio
   import disnake
   
   # 初始化机器人实例（根据你的需求设置intents）
   Client = disnake.Client(intents=disnake.Intents.all())
   # 保存事件循环实例，方便后续跨线程调用
   bot_loop = None
   
   def RunBot():
       global bot_loop
       # 为子线程创建独立事件循环
       bot_loop = asyncio.new_event_loop()
       asyncio.set_event_loop(bot_loop)
       try:
           # 用start代替run，避免自动清理逻辑冲突
           bot_loop.run_until_complete(Client.start("你的机器人token"))
       except KeyboardInterrupt:
           # 优雅关闭机器人
           bot_loop.run_until_complete(Client.close())
       finally:
           bot_loop.close()
   
   async def CheckForRole(GuildId, RoleId, UserId):
       # 原有的角色检查逻辑
       guild = Client.get_guild(GuildId)
       if not guild:
           return False
       member = guild.get_member(UserId)
       return member and any(role.id == RoleId for role in member.roles)
   

2. 调整Quart路由中的跨线程调用
   如果需要在Quart的异步路由中调用机器人的异步方法（比如CheckForRole），不能直接await，需要用asyncio.run_coroutine_threadsafe提交到机器人的事件循环执行：

   @Application.route('/dashboard')
   async def dashboard():
       for Guild in await DiscordOAuth2Session.fetch_guilds():
           if Guild.id == GUILD_ID:
               User = await DiscordOAuth2Session.fetch_user()
               # 替换原来的await Main.CheckForRole(...)
               future = asyncio.run_coroutine_threadsafe(
                   Main.CheckForRole(GuildId=GUILD_ID, RoleId=ROLE_ID, UserId=User.id),
                   Main.bot_loop
               )
               # 同步获取结果，或用await asyncio.wrap_future(future)转为异步
               has_role = future.result()
               if has_role:
                   InformationLogManager.LogInformation(
                       DiscordUserId = User.id,
                       IPAddress = quart.request.remote_addr,
                       Email = User.email
                   )
                   return await quart.render_template("dashboard.html", User = User)
               else:
                   break
           else:
               continue
       return await quart.render_template("access_denied.html"), 401
   

3. 保留原有的线程启动逻辑
   Application.before_serving中的线程启动代码可以保留，确保机器人在Quart服务启动时自动启动。

为什么直接用Python解释器运行正常？ #

直接运行时，Quart的事件循环在主线程初始化，子线程的事件循环可以正常创建且生命周期管理宽松；而Uvicorn作为ASGI服务器，对事件循环的生命周期管理更严格，Windows的ProactorEventLoop在多线程场景下的兼容性问题被触发，导致异常。

内容的提问来源于stack exchange，提问作者Untitled Master