Chris Withers wrote:
> Chris Withers wrote:
>> raise exc.InvalidRequestError("Can't reconnect until invalid
>> transaction is rolled back")
>> sqlalchemy.exc.InvalidRequestError: Can't reconnect until invalid
>> transaction is rolled back
>>
>> Asking here as it sounds like it might be related.
>> It occurred transiently, though, and appears to have resolved itself
>> without any intervention. Where would I look to find out what caused the
>> invalid transaction and how it was rolled back?
>
> We've had this occur again, wondered if anyone had any suggestions...
>
> So, the first error is this:
>
> return session.query(Feed).filter(Feed.enabled==True).all()
> File
> "/usr/lib/python2.5/site-packages/SQLAlchemy-0.5.8-py2.5.egg/sqlalchemy/orm/query.py",
> line 1267, in all
> return list(self)
> File
> "/usr/lib/python2.5/site-packages/SQLAlchemy-0.5.8-py2.5.egg/sqlalchemy/orm/query.py",
> line 1361, in __iter__
> return self._execute_and_instances(context)
> File
> "/usr/lib/python2.5/site-packages/SQLAlchemy-0.5.8-py2.5.egg/sqlalchemy/orm/query.py",
> line 1364, in _execute_and_instances
> result = self.session.execute(querycontext.statement,
> params=self._params, mapper=self._mapper_zero_or_none())
> File
> "/usr/lib/python2.5/site-packages/SQLAlchemy-0.5.8-py2.5.egg/sqlalchemy/orm/session.py",
> line 753, in execute
> clause, params or {})
> File
> "/usr/lib/python2.5/site-packages/SQLAlchemy-0.5.8-py2.5.egg/sqlalchemy/engine/base.py",
> line 824, in execute
> return Connection.executors[c](self, object, multiparams, params)
> File
> "/usr/lib/python2.5/site-packages/SQLAlchemy-0.5.8-py2.5.egg/sqlalchemy/engine/base.py",
> line 874, in _execute_clauseelement
> return self.__execute_context(context)
> File
> "/usr/lib/python2.5/site-packages/SQLAlchemy-0.5.8-py2.5.egg/sqlalchemy/engine/base.py",
> line 896, in __execute_context
> self._cursor_execute(context.cursor, context.statement,
> context.parameters[0], context=context)
> File
> "/usr/lib/python2.5/site-packages/SQLAlchemy-0.5.8-py2.5.egg/sqlalchemy/engine/base.py",
> line 950, in _cursor_execute
> self._handle_dbapi_exception(e, statement, parameters, cursor,
> context)
> File
> "/usr/lib/python2.5/site-packages/SQLAlchemy-0.5.8-py2.5.egg/sqlalchemy/engine/base.py",
> line 931, in _handle_dbapi_exception
> raise exc.DBAPIError.instance(statement, parameters, e,
> connection_invalidated=is_disconnect)
> sqlalchemy.exc.OperationalError: (OperationalError) (2006, 'MySQL server
> has gone away') u'SELECT ...
>
> So, my guess is that we're not handling this error correctly.
> How should we be handling it?
you have to rollback the current transaction, and either throw an error or
try the whole transaction again.
> line 576, in connection
> raise exc.InvalidRequestError("Can't reconnect until invalid
> transaction is rolled back")
> sqlalchemy.exc.InvalidRequestError: Can't reconnect until invalid
> transaction is rolled back
>
> ...until the app was restarted.
>
MySQL disconnected. your transaction was gone. SQLA will reconnect, but
not until you've let it know that you've agreed to chuck your current
transaction on the app side, since its gone on the DB side.
as always, none of these problems ever occur (well disconnects, but the
app will recover), if you ensure that you are doing:
try:
do_my_stuff()
except:
Session.rollback()
raise
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