How can I efficiently manage database connections in FastAPI with SQLAlchemy and avoid 'Too many connections' errors?
I'm relatively new to this, so bear with me. This might be a silly question, but I'm relatively new to this, so bear with me... I'm working on a personal project and I'm building a FastAPI application using SQLAlchemy for database interactions, but I'm running into issues with connection handling. My app sometimes throws the behavior `sqlalchemy.exc.OperationalError: (psycopg2.OperationalError) FATAL: too many connections for user "my_user"`. I've read that connection pooling is essential, but I'm unsure how to implement it correctly in this context. Here's a simplified version of my setup: ```python from fastapi import FastAPI, Depends from sqlalchemy import create_engine, Column, Integer, String from sqlalchemy.ext.declarative import declarative_base from sqlalchemy.orm import sessionmaker, Session DATABASE_URL = "postgresql://my_user:my_password@localhost/my_database" Base = declarative_base() # Create an engine with connection pooling engine = create_engine(DATABASE_URL, pool_size=10, max_overflow=20) SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine) app = FastAPI() class User(Base): __tablename__ = 'users' id = Column(Integer, primary_key=True, index=True) name = Column(String, index=True) # Dependency to get the SQLAlchemy session async def get_db() -> Session: db = SessionLocal() try: yield db finally: db.close() @app.get("/users/{user_id}") async def read_user(user_id: int, db: Session = Depends(get_db)): return db.query(User).filter(User.id == user_id).first() ``` While this approach seems correct, I often notice high connection counts in my PostgreSQL database when I run load tests. I have also tried adjusting the connection pool settings, but the errors continue. Can someone provide guidance on best practices for managing database connections in FastAPI with SQLAlchemy? What configurations or patterns should I consider to prevent hitting the connection limit? Any ideas what could be causing this? This is part of a larger CLI tool I'm building. My development environment is macOS.