Issues with Async Database Calls in FastAPI During Testing Phase
I'm stuck on something that should probably be simple. I'm experimenting with I've searched everywhere and can't find a clear answer..... I'm working on a personal project and Currently developing a FastAPI application where database interactions are handled asynchronously using SQLAlchemy. During the testing phase, I've encountered unexpected timeouts when executing multiple concurrent requests that involve database queries. To illustrate, here's a simplified snippet of the code: ```python from fastapi import FastAPI, HTTPException from sqlalchemy.ext.asyncio import AsyncSession, create_async_engine from sqlalchemy.orm import sessionmaker app = FastAPI() DATABASE_URL = "postgresql+asyncpg://user:password@localhost/db" engine = create_async_engine(DATABASE_URL, echo=True) AsyncSessionLocal = sessionmaker(bind=engine, class_=AsyncSession, expire_on_commit=False) @app.get("/items/{item_id}") async def get_item(item_id: int): async with AsyncSessionLocal() as session: query = await session.execute(select(Item).where(Item.id == item_id)) item = query.scalars().first() if item is None: raise HTTPException(status_code=404, detail="Item not found") return item ``` While testing the endpoints using `pytest` and `httpx`, I set up multiple async requests to simulate user traffic: ```python import pytest import httpx @pytest.mark.asyncio async def test_get_items(): async with httpx.AsyncClient() as client: tasks = [client.get("/items/1"), client.get("/items/2")] responses = await asyncio.gather(*tasks) assert responses[0].status_code == 200 assert responses[1].status_code == 200 ``` The tests intermittently fail with timeout errors, specifically around the database calls. Profiling the application indicated that when several requests hit the database simultaneously, the connection pool is maxing out, causing delays. I initially tried increasing the connection pool size in the database settings, but the issue persists: ```python from sqlalchemy.ext.asyncio import create_async_engine engine = create_async_engine(DATABASE_URL, pool_size=20, max_overflow=0) ``` Additionally, I’ve set the database connection timeout, but it doesn’t appear to resolve the problem. Could it be that I'm not awaiting correctly within my route handlers? Or is there a need for improved connection management? Any suggestions on best practices for handling async database calls in FastAPI under load would be greatly appreciated. For context: I'm using Python on Ubuntu. Any help would be greatly appreciated! For context: I'm using Python on Ubuntu. Any help would be greatly appreciated! This issue appeared after updating to Python 3.9. Thanks in advance!