Flask 应用程序中的第二个请求是否有修复 'MySQL connection not available' 的解决方案？

Question

我是运行本地和生产服务器上的 Flask 应用程序。我对本地没有问题，我在生产服务器上每第二个数据库请求都面临 'MySQL connection not available'。重新加载或执行回滚操作后，正在执行，但问题重复。我通过将 pool_recycle、'wait_timeout' 和其他超时更改为相同值 1600 尝试了互联网上可用的主要解决方案，但没有奏效。我终于销毁了应用程序并在服务器上重新安装了所有内容，但问题仍然存在。请帮忙解决，谢谢。

我的制作MySQL配置：

class ProductionConfig(Config):
    SECRET_KEY = 'secret_key'
    DEBUG=False
    SQLALCHEMY_DATABASE_URI = "mysql+pymysql://{username}: 
        {password}@{hostname}/{databasename}".format(
           username="myusername",
           password="password",
           hostname="myhostname",
           databasename="mydatabase",
    )
    SQLALCHEMY_POOL_RECYCLE = 299
    SQLALCHEMY_TRACK_MODIFICATIONS = False

错误信息：

Exception on /add_questions/1/2 [POST]
Traceback (most recent call last):
  File "/home/ulznrcvr/virtualenv/jaihindpro/3.6/lib/python3.6/site-packages/pymysql/connections.py", line 713, in _write_bytes
    self._sock.sendall(data)
ConnectionResetError: [Errno 104] Connection reset by peer

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/ulznrcvr/virtualenv/jaihindpro/3.6/lib/python3.6/site-packages/sqlalchemy/engine/base.py", line 1248, in _execute_context
    cursor, statement, parameters, context
  File "/home/ulznrcvr/virtualenv/jaihindpro/3.6/lib/python3.6/site-packages/sqlalchemy/engine/default.py", line 590, in do_execute
    cursor.execute(statement, parameters)
  File "/home/ulznrcvr/virtualenv/jaihindpro/3.6/lib/python3.6/site-packages/pymysql/cursors.py", line 170, in execute
    result = self._query(query)
  File "/home/ulznrcvr/virtualenv/jaihindpro/3.6/lib/python3.6/site-packages/pymysql/cursors.py", line 328, in _query
    conn.query(q)
  File "/home/ulznrcvr/virtualenv/jaihindpro/3.6/lib/python3.6/site-packages/pymysql/connections.py", line 516, in query
    self._execute_command(COMMAND.COM_QUERY, sql)
  File "/home/ulznrcvr/virtualenv/jaihindpro/3.6/lib/python3.6/site-packages/pymysql/connections.py", line 771, in _execute_command
    self._write_bytes(packet)
  File "/home/ulznrcvr/virtualenv/jaihindpro/3.6/lib/python3.6/site-packages/pymysql/connections.py", line 718, in _write_bytes
    "MySQL server has gone away (%r)" % (e,))
pymysql.err.OperationalError: (2006, "MySQL server has gone away (ConnectionResetError(104, 'Connection reset by peer'))")

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/home/ulznrcvr/virtualenv/jaihindpro/3.6/lib/python3.6/site-packages/flask/app.py", line 2447, in wsgi_app
    response = self.full_dispatch_request()
  File "/home/ulznrcvr/virtualenv/jaihindpro/3.6/lib/python3.6/site-packages/flask/app.py", line 1952, in full_dispatch_request
    rv = self.handle_user_exception(e)
  File "/home/ulznrcvr/virtualenv/jaihindpro/3.6/lib/python3.6/site-packages/flask/app.py", line 1821, in handle_user_exception
    reraise(exc_type, exc_value, tb)
  File "/home/ulznrcvr/virtualenv/jaihindpro/3.6/lib/python3.6/site-packages/flask/_compat.py", line 39, in reraise
    raise value
  File "/home/ulznrcvr/virtualenv/jaihindpro/3.6/lib/python3.6/site-packages/flask/app.py", line 1950, in full_dispatch_request
    rv = self.dispatch_request()
  File "/home/ulznrcvr/virtualenv/jaihindpro/3.6/lib/python3.6/site-packages/flask/app.py", line 1936, in dispatch_request
    return self.view_functions[rule.endpoint](**req.view_args)
  File "/home/ulznrcvr/virtualenv/jaihindpro/3.6/lib/python3.6/site-packages/flask_login/utils.py", line 270, in decorated_view
    elif not current_user.is_authenticated:
  File "/home/ulznrcvr/virtualenv/jaihindpro/3.6/lib/python3.6/site-packages/werkzeug/local.py", line 347, in __getattr__
    return getattr(self._get_current_object(), name)
  File "/home/ulznrcvr/virtualenv/jaihindpro/3.6/lib/python3.6/site-packages/werkzeug/local.py", line 306, in _get_current_object
    return self.__local()
  File "/home/ulznrcvr/virtualenv/jaihindpro/3.6/lib/python3.6/site-packages/flask_login/utils.py", line 26, in <lambda>
    current_user = LocalProxy(lambda: _get_user())
  File "/home/ulznrcvr/virtualenv/jaihindpro/3.6/lib/python3.6/site-packages/flask_login/utils.py", line 346, in _get_user
    current_app.login_manager._load_user()
  File "/home/ulznrcvr/virtualenv/jaihindpro/3.6/lib/python3.6/site-packages/flask_login/login_manager.py", line 318, in _load_user
    user = self._user_callback(user_id)
  File "/home/ulznrcvr/jaihindpro/application/auth/views.py", line 26, in load_user
    return User.query.get(int(user_id))
  File "/home/ulznrcvr/virtualenv/jaihindpro/3.6/lib/python3.6/site-packages/sqlalchemy/orm/query.py", line 1004, in get
    return self._get_impl(ident, loading.load_on_pk_identity)
  File "/home/ulznrcvr/virtualenv/jaihindpro/3.6/lib/python3.6/site-packages/sqlalchemy/orm/query.py", line 1121, in _get_impl
    return db_load_fn(self, primary_key_identity)
  File "/home/ulznrcvr/virtualenv/jaihindpro/3.6/lib/python3.6/site-packages/sqlalchemy/orm/loading.py", line 287, in load_on_pk_identity
    return q.one()
  File "/home/ulznrcvr/virtualenv/jaihindpro/3.6/lib/python3.6/site-packages/sqlalchemy/orm/query.py", line 3360, in one
    ret = self.one_or_none()
  File "/home/ulznrcvr/virtualenv/jaihindpro/3.6/lib/python3.6/site-packages/sqlalchemy/orm/query.py", line 3329, in one_or_none
    ret = list(self)
  File "/home/ulznrcvr/virtualenv/jaihindpro/3.6/lib/python3.6/site-packages/sqlalchemy/orm/query.py", line 3405, in __iter__
    return self._execute_and_instances(context)
  File "/home/ulznrcvr/virtualenv/jaihindpro/3.6/lib/python3.6/site-packages/sqlalchemy/orm/query.py", line 3430, in _execute_and_instances
    result = conn.execute(querycontext.statement, self._params)
  File "/home/ulznrcvr/virtualenv/jaihindpro/3.6/lib/python3.6/site-packages/sqlalchemy/engine/base.py", line 984, in execute
    return meth(self, multiparams, params)
  File "/home/ulznrcvr/virtualenv/jaihindpro/3.6/lib/python3.6/site-packages/sqlalchemy/sql/elements.py", line 293, in _execute_on_connection
    return connection._execute_clauseelement(self, multiparams, params)
  File "/home/ulznrcvr/virtualenv/jaihindpro/3.6/lib/python3.6/site-packages/sqlalchemy/engine/base.py", line 1103, in _execute_clauseelement
    distilled_params,
  File "/home/ulznrcvr/virtualenv/jaihindpro/3.6/lib/python3.6/site-packages/sqlalchemy/engine/base.py", line 1288, in _execute_context
    e, statement, parameters, cursor, context
  File "/home/ulznrcvr/virtualenv/jaihindpro/3.6/lib/python3.6/site-packages/sqlalchemy/engine/base.py", line 1482, in _handle_dbapi_exception
    sqlalchemy_exception, with_traceback=exc_info[2], from_=e
  File "/home/ulznrcvr/virtualenv/jaihindpro/3.6/lib/python3.6/site-packages/sqlalchemy/util/compat.py", line 178, in raise_
    raise exception
  File "/home/ulznrcvr/virtualenv/jaihindpro/3.6/lib/python3.6/site-packages/sqlalchemy/engine/base.py", line 1248, in _execute_context
    cursor, statement, parameters, context
  File "/home/ulznrcvr/virtualenv/jaihindpro/3.6/lib/python3.6/site-packages/sqlalchemy/engine/default.py", line 590, in do_execute
    cursor.execute(statement, parameters)
  File "/home/ulznrcvr/virtualenv/jaihindpro/3.6/lib/python3.6/site-packages/pymysql/cursors.py", line 170, in execute
    result = self._query(query)
  File "/home/ulznrcvr/virtualenv/jaihindpro/3.6/lib/python3.6/site-packages/pymysql/cursors.py", line 328, in _query
    conn.query(q)
  File "/home/ulznrcvr/virtualenv/jaihindpro/3.6/lib/python3.6/site-packages/pymysql/connections.py", line 516, in query
    self._execute_command(COMMAND.COM_QUERY, sql)
  File "/home/ulznrcvr/virtualenv/jaihindpro/3.6/lib/python3.6/site-packages/pymysql/connections.py", line 771, in _execute_command
    self._write_bytes(packet)
  File "/home/ulznrcvr/virtualenv/jaihindpro/3.6/lib/python3.6/site-packages/pymysql/connections.py", line 718, in _write_bytes
    "MySQL server has gone away (%r)" % (e,))
sqlalchemy.exc.OperationalError: (pymysql.err.OperationalError) (2006, "MySQL server has gone away (ConnectionResetError(104, 'Connection reset by peer'))")
[SQL: SELECT user.id AS user_id, user.student_id AS user_student_id, user.role_id AS user_role_id, user.course_id AS user_course_id, user.sub_course_id AS user_sub_course_id, user.batch_id AS user_batch_id, user.full_name AS user_full_name, user.email AS user_email, user.phone_number AS user_phone_number, user.password AS user_password, user.active AS user_active, user.confirmed AS user_confirmed, user.confirmed_date AS user_confirmed_date, user.subscribed AS user_subscribed, user.start_date AS user_start_date, user.end_date AS user_end_date, user.re_url AS user_re_url, user.online AS user_online 
FROM user 
WHERE user.id = %(param_1)s]
[parameters: {'param_1': 2}]
(Background on this error at: http://sqlalche.me/e/e3q8)

Answer 1

我自己弄明白了，我在引擎设置中将“pool_pre_ping”属性标记为“True”。

SQLALCHEMY_ENGINE_OPTIONS = {
        "pool_pre_ping": True, 
        "pool_recycle": 300,
    }

参考：https://medium.com/@heyjcmc/controlling-the-flask-sqlalchemy-engine-a0f8fae15b47

Flask 应用程序中的第二个请求是否有修复 'MySQL connection not available' 的解决方案？

Is there a solution in fixing 'MySQL connection not available' for very second request in Flask application?

mysql

mysql-connector

flask

python-3.x

flask-sqlalchemy