Issues with Async Database Operations in FastAPI Leading to Connection Errors
I'm performance testing and I've looked through the documentation and I'm still confused about I'm migrating some code and I'm working on a personal project and I'm encountering connection issues while performing async database operations in my FastAPI application using SQLAlchemy 1.4..... I have a simple setup where I initialize the database connection using `async_session = sessionmaker(bind=engine, class_=AsyncSession, expire_on_commit=False)` and I’m using dependency injection to get the session in my route handlers. However, I keep running into an error that states: `sqlalchemy.exc.InterfaceError: (asyncpg.exceptions.ConnectionDoesNotExist) connection does not exist`. Here's a snippet of my route handler: ```python from fastapi import FastAPI, Depends, HTTPException from sqlalchemy.ext.asyncio import AsyncSession, create_async_engine, sessionmaker from sqlalchemy.orm import declarative_base DATABASE_URL = "postgresql+asyncpg://user:password@localhost/dbname" engine = create_async_engine(DATABASE_URL, echo=True) async_session = sessionmaker(engine, expire_on_commit=False, class_=AsyncSession) Base = declarative_base() app = FastAPI() async def get_db() -> AsyncSession: async with async_session() as session: yield session @app.get("/items/{item_id}") async def read_item(item_id: int, db: AsyncSession = Depends(get_db)): result = await db.execute(select(Item).where(Item.id == item_id)) item = result.scalars().first() if item is None: raise HTTPException(status_code=404, detail="Item not found") return item ``` I’ve checked my database connection settings and they seem fine. The database is running, and I can connect to it using the same credentials in a regular synchronous script. I’ve also tried wrapping the route handler in a try-except block to catch exceptions, but that hasn’t helped me identify the root cause. Any insights on why my application might be having trouble with async connections and how I can resolve this? For context: I'm using Python on macOS. What am I doing wrong? I'm coming from a different tech stack and learning Python. How would you solve this? My team is using Python for this desktop app. Any advice would be much appreciated. For context: I'm using Python on Ubuntu 22.04.