python - sqlalchemy:使用装饰器为多个函数提供线程安全 session

Question

我正在研究类似 here 的东西(带有 sqlalchemy 的多线程应用程序)，所以我明白，我应该为每个数据库查询创建一个新 session 。

我想知道，如果为每个需要 DB 访问的方法使用装饰器是否有意义，或者是否存在使用这种方法的陷阱。装饰器是按照 the last example here 构建的.

def dbconnect(func):
    def inner(*args, **kwargs):
        session = Session()  # with all the requirements
        try:
            func(*args, session=session, **kwargs)
            session.commit()
        except:
            session.rollback()
            raise
        finally:
            session.close()
    return inner

@dbconnect
def some_function(some, arguments, session)
    session.query(...) # no commit, close, rollback required

some_function("many", "different_arguments") 
#session is not required, since provided by decorator

这将使为任何函数提供线程安全的数据库访问变得相当容易，而不需要实现整个 try-except-finally-stuff 冗余，但我不确定这种方法是否是故障安全的和 pythonic，或者是否存在其他最佳实践。

Answer 1

我认为在这里使用 scoped_session 是有意义的，可能是这样的:

session_factory = sessionmaker(bind=some_engine)
Session = scoped_session(session_factory)

def dbconnect(func):
    def inner(*args, **kwargs):
        session = Session()  # (this is now a scoped session)
        try:
            func(*args, **kwargs) # No need to pass session explicitly
            session.commit()
        except:
            session.rollback()
            raise
        finally:
            Session.remove()  # NOTE: *remove* rather than *close* here
    return inner

@dbconnect
def some_function(some, arguments):
    session = Session()
    # 'session' is  now a handle to the *same* session as in the decorator
    session.query(...) # no commit, close, rollback required

some_function("many", "different_arguments") 
#session is not required, since provided by decorator

(警告:未经测试)