FastAPI Async Endpoint with SQLAlchemy and pg8000 Connection Issues in Docker
I'm reviewing some code and Hey everyone, I'm running into an issue that's driving me crazy. I'm upgrading from an older version and I'm working with a challenging scenario while deploying my FastAPI application with SQLAlchemy and pg8000 inside a Docker container... My setup works flawlessly on my local machine, but when I run it in Docker, I get a `psycopg2.OperationalError: connection to server failed` behavior. I suspect it may be related to the async database connection management. Here’s a snippet of how I’m initializing the database connection: ```python from fastapi import FastAPI, Depends from sqlalchemy.ext.asyncio import create_async_engine, AsyncSession from sqlalchemy.orm import sessionmaker from sqlalchemy.ext.declarative import declarative_base DATABASE_URL = "postgresql+pg8000://user:password@db:5432/mydatabase" engine = create_async_engine(DATABASE_URL, echo=True) Base = declarative_base() async_session = sessionmaker(engine, expire_on_commit=False, class_=AsyncSession) app = FastAPI() async def get_db() -> AsyncSession: async with async_session() as session: yield session ``` And here’s the relevant part of my Dockerfile: ```dockerfile FROM python:3.10-slim WORKDIR /app COPY requirements.txt . RUN pip install -r requirements.txt COPY . . CMD ["uvicorn", "main:app", "--host", "0.0.0.0", "--port", "8000"] ``` I’m also using Docker Compose for the database service, and my `docker-compose.yml` looks like this: ```yaml version: '3.8' services: db: image: postgres:latest environment: POSTGRES_USER: user POSTGRES_PASSWORD: password POSTGRES_DB: mydatabase ports: - "5432:5432" web: build: . ports: - "8000:8000" depends_on: - db ``` When I try to access the FastAPI endpoint, I see connection issues, and it seems the database service may not be ready when the FastAPI app attempts to connect. I tried adding a health check to the database service, but it didn’t resolve the scenario. Any suggestions on ensuring that the FastAPI app waits for the database to be up before trying to connect? I'm working on a service that needs to handle this. What am I doing wrong? I'm working on a microservice that needs to handle this. I'd really appreciate any guidance on this. This is my first time working with Python 3.11. The project is a microservice built with Python. Any feedback is welcome!