Handling Memory Leaks in a FastAPI Application with SQLAlchemy Models
I'm migrating some code and I've been banging my head against this for hours... I tried several approaches but none seem to work. I'm facing a troubling memory leak in my FastAPI application that's using SQLAlchemy for database interactions. After several requests to my endpoints, the memory usage continues to grow without being released, which leads to performance degradation over time. I've been using FastAPI version 0.68.0 and SQLAlchemy version 1.4.25. My models are fairly standard, but I'm concerned that the way I'm managing sessions might be contributing to the problem. Here's a simplified version of my code where I define a SQLAlchemy model and use it in a FastAPI endpoint: ```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 = "sqlite:///./test.db" engine = create_engine(DATABASE_URL) SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine) Base = declarative_base() class User(Base): __tablename__ = "users" id = Column(Integer, primary_key=True, index=True) name = Column(String, index=True) app = FastAPI() @app.get("/users/{user_id}") async def read_user(user_id: int, db: Session = Depends(SessionLocal)): user = db.query(User).filter(User.id == user_id).first() return user ``` Despite using the `Depends` for the database session, I suspect the sessions are not being closed properly after each request. I've also tried adding a middleware to monitor memory usage, and I see it spikes significantly after several requests, particularly when I hit a looped endpoint that performs multiple database queries in a single request. Even with FastAPI's dependency injection, I worry that the way I’m managing the session lifecycle might not be ideal. I’ve considered using the `async with` syntax for session management but I'm not sure how to refactor my code to implement this correctly. Has anyone dealt with this issue? What best practices can I follow to ensure that the sessions are being managed properly and that no memory leak occurs? Any suggestions would be greatly appreciated! My development environment is Linux. For context: I'm using Python on Linux. Am I missing something obvious? I've been using Python for about a year now. What's the correct way to implement this?