👀 Views: 31 💬 Answers: 1 📅 Created: 2025-06-04

fastapi sqlalchemy asyncio Python

I'm having a hard time understanding I'm working on a personal project and I'm working on a FastAPI application using SQLAlchemy, and I'm running into issues when trying to handle asynchronous database sessions. My setup includes FastAPI 0.68.0 and SQLAlchemy 1.4.22, and I'm using async/await to interact with a PostgreSQL database. When I attempt to run a simple query using the session, I get the following behavior: ``` sqlalchemy.exc.OperationalError: (psycopg2.OperationalError) connection to server failed ``` Here's a snippet of my code showing how I set up the database session: ```python from fastapi import FastAPI, Depends from sqlalchemy.ext.asyncio import AsyncSession, create_async_engine, async_sessionmaker from sqlalchemy.orm import sessionmaker, declarative_base DATABASE_URL = "postgresql+asyncpg://user:password@localhost/dbname" engine = create_async_engine(DATABASE_URL, echo=True) Base = declarative_base() async_session = async_sessionmaker(engine, expire_on_commit=False) app = FastAPI() async def get_db() -> AsyncSession: async with async_session() as session: yield session ``` And in my route handler, I’m trying to fetch data like this: ```python @app.get("/items/{item_id}") async def read_item(item_id: int, db: AsyncSession = Depends(get_db)): result = await db.execute("SELECT * FROM items WHERE id = :id", {'id': item_id}) item = result.fetchone() return item ``` I have verified that the PostgreSQL server is running and accessible, as I can connect to it using psql without issues. I suspect it might be related to the way I’m managing the asynchronous sessions or the database configuration itself. I've tried changing the connection string format and ensuring the database URL is correct, but nothing seems to resolve the scenario. Any insights on how to properly manage asynchronous connections with SQLAlchemy in FastAPI or potential pitfalls I should be aware of would be greatly appreciated. I'm working on a application that needs to handle this. How would you solve this? I'm using Python latest in this project. I'm using Python latest in this project. Thanks in advance!