SQLAlchemy会话在几分钟后不断下降

Question

我正在编写一个需要与许多数据存储区通信的Flask API，AWS RDS上的Postgres就是其中之一。我想避免使用Flask-SQLAlchemy（尝试减少包依赖），并且鉴于我的用例非常简单，我认为标准的SQLAlchemy库应该足够了。这是我的models.py文件：

class DriverPostgres:
    def __init__(self):
        self.connector = PostgresCredentials()
        self.connection_str = 'postgresql+psycopg2://{}:{}@{}/{}'.format(...)
        self.engine = create_engine(self.connection_str)
        self.Session = scoped_session(
            sessionmaker(autocommit=False, autoflush=True, bind=self.engine))
        Base.metadata.create_all(bind=self.engine)

    def get_user_by_email(self, email):
        session = self.Session()
        result = session.query(User).filter_by(email=email).first()
        self.Session.remove()
        return result

    def register_user(self, ...):
        user = User(...)
        session = self.Session()
        session.add(user)
        try:
            session.commit()
        except IntegrityError:
            return False
        finally:
            self.Session.remove()
        return True

在我的Flask应用server.py文件中，我在应用顶部导入DriverPostgres并实例化driver_postgres = DriverPostgres()，在处理请求时，我调用driver_postgres.get_user_by_email()。首次加载应用程序时，此逻辑非常有效。我可以根据需要发送尽可能多的请求，没有任何问题。但是，如果我等待几分钟并再次点击应用程序，我会收到以下错误：

Traceback (most recent call last):
  File "/Users/user/.virtualenvs/demo/lib/python3.6/site-packages/flask/app.py", line 2309, in __call__
    return self.wsgi_app(environ, start_response)
  File "/Users/user/.virtualenvs/demo/lib/python3.6/site-packages/flask/app.py", line 2295, in wsgi_app
    response = self.handle_exception(e)
  File "/Users/user/.virtualenvs/demo/lib/python3.6/site-packages/flask_cors/extension.py", line 161, in wrapped_function
    return cors_after_request(app.make_response(f(*args, **kwargs)))
  File "/Users/user/.virtualenvs/demo/lib/python3.6/site-packages/flask/app.py", line 1741, in handle_exception
    reraise(exc_type, exc_value, tb)
  File "/Users/user/.virtualenvs/demo/lib/python3.6/site-packages/flask/_compat.py", line 35, in reraise
    raise value
  File "/Users/user/.virtualenvs/demo/lib/python3.6/site-packages/flask/app.py", line 2292, in wsgi_app
    response = self.full_dispatch_request()
  File "/Users/user/.virtualenvs/demo/lib/python3.6/site-packages/flask/app.py", line 1815, in full_dispatch_request
    rv = self.handle_user_exception(e)
  File "/Users/user/.virtualenvs/demo/lib/python3.6/site-packages/flask_cors/extension.py", line 161, in wrapped_function
    return cors_after_request(app.make_response(f(*args, **kwargs)))
  File "/Users/user/.virtualenvs/demo/lib/python3.6/site-packages/flask/app.py", line 1718, in handle_user_exception
    reraise(exc_type, exc_value, tb)
  File "/Users/user/.virtualenvs/demo/lib/python3.6/site-packages/flask/_compat.py", line 35, in reraise
    raise value
  File "/Users/user/.virtualenvs/demo/lib/python3.6/site-packages/flask/app.py", line 1813, in full_dispatch_request
    rv = self.dispatch_request()
  File "/Users/user/.virtualenvs/demo/lib/python3.6/site-packages/flask/app.py", line 1799, in dispatch_request
    return self.view_functions[rule.endpoint](**req.view_args)
  File "/Users/userserver.py", line 118, in login
    response = driver_postgres.check_password(email, password)
  File "/Users/usermodels.py", line 125, in check_password
    user_to_check = self.get_user_by_email(email)
  File "/Users/usermodels.py", line 154, in get_user_by_email
    result = session.query(User).filter_by(email=email).first()
  File "/Users/user/.virtualenvs/demo/lib/python3.6/site-packages/sqlalchemy/orm/query.py", line 2835, in first
    ret = list(self[0:1])
  File "/Users/user/.virtualenvs/demo/lib/python3.6/site-packages/sqlalchemy/orm/query.py", line 2627, in __getitem__
    return list(res)
  File "/Users/user/.virtualenvs/demo/lib/python3.6/site-packages/sqlalchemy/orm/query.py", line 2935, in __iter__
    return self._execute_and_instances(context)
  File "/Users/user/.virtualenvs/demo/lib/python3.6/site-packages/sqlalchemy/orm/query.py", line 2958, in _execute_and_instances
    result = conn.execute(querycontext.statement, self._params)
  File "/Users/user/.virtualenvs/demo/lib/python3.6/site-packages/sqlalchemy/engine/base.py", line 948, in execute
    return meth(self, multiparams, params)
  File "/Users/user/.virtualenvs/demo/lib/python3.6/site-packages/sqlalchemy/sql/elements.py", line 269, in _execute_on_connection
    return connection._execute_clauseelement(self, multiparams, params)
  File "/Users/user/.virtualenvs/demo/lib/python3.6/site-packages/sqlalchemy/engine/base.py", line 1060, in _execute_clauseelement
    compiled_sql, distilled_params
  File "/Users/user/.virtualenvs/demo/lib/python3.6/site-packages/sqlalchemy/engine/base.py", line 1200, in _execute_context
    context)
  File "/Users/user/.virtualenvs/demo/lib/python3.6/site-packages/sqlalchemy/engine/base.py", line 1413, in _handle_dbapi_exception
    exc_info
  File "/Users/user/.virtualenvs/demo/lib/python3.6/site-packages/sqlalchemy/util/compat.py", line 203, in raise_from_cause
    reraise(type(exception), exception, tb=exc_tb, cause=cause)
  File "/Users/user/.virtualenvs/demo/lib/python3.6/site-packages/sqlalchemy/util/compat.py", line 186, in reraise
    raise value.with_traceback(tb)
  File "/Users/user/.virtualenvs/demo/lib/python3.6/site-packages/sqlalchemy/engine/base.py", line 1193, in _execute_context
    context)
  File "/Users/user/.virtualenvs/demo/lib/python3.6/site-packages/sqlalchemy/engine/default.py", line 508, in do_execute
    cursor.execute(statement, parameters)
sqlalchemy.exc.OperationalError: (psycopg2.OperationalError) server closed the connection unexpectedly
    This probably means the server terminated abnormally
    before or while processing the request.
 [SQL: ...] (Background on this error at: http://sqlalche.me/e/e3q8)

这是相当严重的。我花了很多时间浏览SO和许多教程，这似乎是一个标准的有效模式，所以我不确定出了什么问题。我不应该删除会话吗？我应该使用@app.teardown_appcontext装饰器（似乎如果我现在就像我现在所做的那样删除会话，我不应该这样做）？我是否应该使用连接池（默认情况下默认情况下QueuePool已启用）？如果它有帮助，我使用所有软件包的最新版本，Python 3.6.5和Postman将请求发送到服务器，该服务器运行在localhost:5000。任何建议都将非常感谢 - 提前感谢！