implementing Database Transactions in SQLAlchemy When Using AsyncIO in FastAPI
I'm stuck trying to I'm stuck on something that should probably be simple... I'm experiencing unexpected behavior when trying to manage database transactions in an async environment with FastAPI and SQLAlchemy. I am using SQLAlchemy 1.4.x, which supports async, but I keep getting the behavior `Transaction is not active` under certain conditions. My setup involves an async FastAPI endpoint that tries to create a new user in the database. The code looks something like this: ```python from fastapi import FastAPI, HTTPException from sqlalchemy.ext.asyncio import AsyncSession, create_async_engine from sqlalchemy.orm import sessionmaker from sqlalchemy.ext.declarative import declarative_base from sqlalchemy import Column, Integer, String DATABASE_URL = "postgresql+asyncpg://user:password@localhost/test" engine = create_async_engine(DATABASE_URL, echo=True) Base = declarative_base() class User(Base): __tablename__ = 'users' id = Column(Integer, primary_key=True, index=True) name = Column(String, index=True) async_session = sessionmaker(engine, class_=AsyncSession, expire_on_commit=False) app = FastAPI() @app.post("/users/") async def create_user(name: str): async with async_session() as session: async with session.begin(): new_user = User(name=name) session.add(new_user) # Trying to commit here leads to an behavior # await session.commit() # This line leads to the behavior return new_user ``` I commented out the `await session.commit()` line because it throws the `Transaction is not active` behavior. I’ve tried wrapping the entire block in a single transaction, but it seems that the session is in an inconsistent state after adding the user. I also checked that the database connection is properly established. Using `session.add(new_user)` without a call to `commit()` does create the user, but I want to ensure the transaction is properly committed to the database. Any insights on what might be going wrong here? Could it be related to how I manage the session or the async flow? Has anyone else encountered this? Has anyone dealt with something similar?