FastAPI: How to Properly Handle Async Dependencies with SQLAlchemy Sessions?
I've spent hours debugging this and I'm trying to debug I'm currently working on a FastAPI application and trying to implement async endpoints that use SQLAlchemy for database interactions... I want to ensure that the session lifecycle is correctly managed, but I'm running into issues with the async context manager. My application is using SQLAlchemy 1.4 and FastAPI 0.68.0. Here's a simplified version of my code: ```python from fastapi import FastAPI, Depends, HTTPException from sqlalchemy.ext.asyncio import AsyncSession, create_async_engine, async_sessionmaker from sqlalchemy.ext.declarative import declarative_base from sqlalchemy.orm import sessionmaker DATABASE_URL = "postgresql+asyncpg://user:password@localhost/dbname" engine = create_async_engine(DATABASE_URL) Base = declarative_base() SessionLocal = async_sessionmaker(bind=engine, expire_on_commit=False) app = FastAPI() async def get_db() -> AsyncSession: async with SessionLocal() as session: yield session @app.get("/users/{user_id}") async def read_user(user_id: int, db: AsyncSession = Depends(get_db)): result = await db.execute(select(User).where(User.id == user_id)) user = result.scalar_one_or_none() if user is None: raise HTTPException(status_code=404, detail="User not found") return user ``` Despite following the documentation, I get this behavior when trying to access the `/users/{user_id}` endpoint: ``` RuntimeError: Task <Task pending name='Task-1' coro=<read_user() running at ...>> got Future <Future pending> attached to a different loop ``` I've confirmed that I am not mixing sync and async operations, and I suspect it might be related to how I'm managing the event loop. I've tried explicitly setting the event loop using `asyncio.set_event_loop()`, but it hasn't solved the scenario. Is there an appropriate way to handle the lifecycle of the SQLAlchemy session in an async FastAPI application? Any insights or suggestions would be greatly appreciated! I'm using Python LTS in this project. I'm open to any suggestions. Thanks, I really appreciate it!