Using SQLAlchemy 0.4.4
I am having a problem with SQLAlchemy where after the application that
uses SQLAlchemy has been sitting overnight and a user makes the first
queries of the day thru the app that uses SA, SQLAlchemy throws an
error saying 'MySQL server has gone away', which I understand the
reason to be that my mysql server has cut the idle connections, but I
have pool_recycle = 3600 set and I thought that was the solution to
keeping connections alive?
After that error message I get two more exceptions when the user tries
the request again of "Can't reconnect until invalid transaction is
rolled back", which I don't understand at all because the application
only queries the DB and never deals with transactions. After those
three attempts, the forth request will go through just fine. :-\ Any
pointers on what I should look for or do?
Here is the full traceback of the exceptions...
Module vendormiddleware.model:47 in by_company_code
>> count = codes.count()
Module sqlalchemy.orm.query:1087 in count
>> return q._count()
Module sqlalchemy.orm.query:1108 in _count
>> return self.session.scalar(s, params=self._params, mapper=self.mapper)
Module sqlalchemy.orm.session:612 in scalar
>> return self.__connection(engine, close_with_result=True).scalar(clause,
>> params or {}, **kwargs)
Module sqlalchemy.engine.base:836 in scalar
>> return self.execute(object, *multiparams, **params).scalar()
Module sqlalchemy.engine.base:846 in execute
>> return Connection.executors[c](self, object, multiparams, params)
Module sqlalchemy.engine.base:897 in execute_clauseelement
>> return self._execute_compiled(elem.compile(dialect=self.dialect,
>> column_keys=keys, inline=len(params) > 1), distilled_params=params)
Module sqlalchemy.engine.base:909 in _execute_compiled
>> self.__execute_raw(context)
Module sqlalchemy.engine.base:918 in __execute_raw
>> self._cursor_execute(context.cursor, context.statement,
>> context.parameters[0], context=context)
Module sqlalchemy.engine.base:962 in _cursor_execute
>> self._handle_dbapi_exception(e, statement, parameters, cursor)
Module sqlalchemy.engine.base:944 in _handle_dbapi_exception
>> raise exceptions.DBAPIError.instance(statement, parameters, e,
>> connection_invalidated=is_disconnect)
OperationalError: (OperationalError) (2006, 'MySQL server has gone
away') u'SELECT count(company.company_id) AS count_1 \nFROM company
\nWHERE company.company_code = %s' [u'CUSTOMER1']
Module vendormiddleware.model:47 in by_company_code
>> count = codes.count()
Module sqlalchemy.orm.query:1087 in count
>> return q._count()
Module sqlalchemy.orm.query:1108 in _count
>> return self.session.scalar(s, params=self._params, mapper=self.mapper)
Module sqlalchemy.orm.session:612 in scalar
>> return self.__connection(engine, close_with_result=True).scalar(clause,
>> params or {}, **kwargs)
Module sqlalchemy.engine.base:836 in scalar
>> return self.execute(object, *multiparams, **params).scalar()
Module sqlalchemy.engine.base:846 in execute
>> return Connection.executors[c](self, object, multiparams, params)
Module sqlalchemy.engine.base:897 in execute_clauseelement
>> return self._execute_compiled(elem.compile(dialect=self.dialect,
>> column_keys=keys, inline=len(params) > 1), distilled_params=params)
Module sqlalchemy.engine.base:906 in _execute_compiled
>> context = self.__create_execution_context(compiled=compiled,
>> parameters=distilled_params)
Module sqlalchemy.engine.base:950 in __create_execution_context
>> return self.engine.dialect.create_execution_context(connection=self,
>> **kwargs)
Module sqlalchemy.databases.mysql:1464 in create_execution_context
>> return MySQLExecutionContext(self, connection, **kwargs)
Module sqlalchemy.engine.default:178 in __init__
>> self.cursor = self.create_cursor()
Module sqlalchemy.engine.default:275 in create_cursor
>> return self._connection.connection.cursor()
Module sqlalchemy.engine.base:583 in connection
>> raise exceptions.InvalidRequestError("Can't reconnect until invalid
>> transaction is rolled back")
InvalidRequestError: Can't reconnect until invalid transaction is
rolled back
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