👀 Views: 0 💬 Answers: 1 📅 Created: 2025-06-06

fastapi asyncio background-tasks sqlalchemy Python

I just started working with Quick question that's been bugging me - I've spent hours debugging this and I'm encountering an issue with FastAPI where background tasks that I've defined as async functions do not seem to complete as expected. I'm using FastAPI v0.68.1 along with an async database session from SQLAlchemy. Here’s a simplified version of my implementation: ```python from fastapi import FastAPI, BackgroundTasks from sqlalchemy.ext.asyncio import AsyncSession, create_async_engine, sessionmaker app = FastAPI() DATABASE_URL = 'sqlite+aiosqlite:///./test.db' engine = create_async_engine(DATABASE_URL, echo=True) AsyncSessionLocal = sessionmaker(bind=engine, class_=AsyncSession, expire_on_commit=False) async def background_task(data: str): # Simulating a long-running task await asyncio.sleep(10) print(f"Processed data: {data}") @app.post("/process/{item_id}") async def process_item(item_id: int, background_tasks: BackgroundTasks): # This is where the task is added to the background background_tasks.add_task(background_task, f'Item {item_id}') return {"message": "Processing started"} ``` When I hit the endpoint, the response is immediate, but the background task doesn’t seem to execute. My console shows that the FastAPI server is responsive, but I never see the output from `print(f"Processed data: {data}")`. I’ve also tried adding logging to the `background_task` to see if it’s being called, but I get nothing. I verified that the `asyncio` loop is running and that there are no uncaught exceptions. I’m also concerned that the database session might be causing an issue, so I tried ensuring the session is closed properly, but that didn't help. Am I missing something when it comes to using async functions in background tasks with FastAPI? Any insights would be appreciated. For reference, this is a production REST API. Any ideas how to fix this? Could someone point me to the right documentation? Could someone point me to the right documentation? Any ideas what could be causing this?