python runtime_error ai_generated true

RuntimeError: no running event loop

ID: python/fastapi-background-task-event-loop

Also available as: JSON · Markdown · 中文
80%Fix Rate
83%Confidence
0Evidence
2025-01-08First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
3.x active — — —

Root Cause

asyncio.get_event_loop() or loop.run_until_complete() is called inside a sync background task or thread where no loop is running.

generic

中文

在没有运行事件循环的同步后台任务或线程中调用了 asyncio.get_event_loop() 或 loop.run_until_complete()。

Workarounds

  1. 90% success 
    Make the background task async:
async def task(): await do_work()
background_tasks.add_task(task)
  2. 82% success 
    In a thread, use asyncio.run(coro()) for self-contained work.

Dead Ends

Common approaches that don't work:

  1. 75% fail

    Creates leaks and doesn't share the server loop; resources bound to another loop fail.

  2. 80% fail

    Blocks the loop and doesn't address the missing loop in the thread.