python runtime_error ai_generated true

RuntimeError: Background task failed: 'NoneType' object has no attribute 'send'

ID: python/starlette-background-task-error

Also available as: JSON · Markdown · 中文
80%Fix Rate
82%Confidence
0Evidence
2024-06-25First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
3.x active — — —

Root Cause

A background task function is not defined as async or is called incorrectly, causing the ASGI server to fail when trying to run it.

generic

中文

后台任务函数未定义为async或调用不正确，导致ASGI服务器尝试运行时失败。

Workarounds

  1. 95% success 
    Define the task as async: async def send_email(email: str):\n    # ...\nthen use BackgroundTask(send_email, email)
  2. 90% success 
    Use Starlette's BackgroundTasks: background_tasks.add_task(send_email, email)

Dead Ends

Common approaches that don't work:

  1. 80% fail

    Calling the background task function directly instead of passing it to BackgroundTask causes immediate execution.

  2. 60% fail

    Making the task synchronous works in some cases but blocks the event loop.