On Aug 25, 2010, at 10:11 PM, Warwick Prince wrote:
> Hi All
>
> This is my first post here, so I wish it were a little more spectacular.. :-)
>
> I have been working happily with SA 0.6.x on Windows 2003 server with MySQL
> and the Sun Python Connector. I have an identical config running (and
> working) on XP.
>
> I was testing my code which had been working perfectly, and suddenly started
> getting this message which I had never seen before;
>
> Traceback (most recent call last):
> File "<pyshell#3>", line 1, in <module>
> e.connect()
> File "C:\Python26\lib\site-packages\sqlalchemy\engine\base.py", line 1731,
> in connect
> return self.Connection(self, **kwargs)
> File "C:\Python26\lib\site-packages\sqlalchemy\engine\base.py", line 821, in
> __init__
> self.__connection = connection or engine.raw_connection()
> File "C:\Python26\lib\site-packages\sqlalchemy\engine\base.py", line 1787,
> in raw_connection
> return self.pool.unique_connection()
> File "C:\Python26\lib\site-packages\sqlalchemy\pool.py", line 135, in
> unique_connection
> return _ConnectionFairy(self).checkout()
> File "C:\Python26\lib\site-packages\sqlalchemy\pool.py", line 329, in
> __init__
> rec = self._connection_record = pool.get()
> File "C:\Python26\lib\site-packages\sqlalchemy\pool.py", line 177, in get
> return self.do_get()
> File "C:\Python26\lib\site-packages\sqlalchemy\pool.py", line 692, in do_get
> con = self.create_connection()
> File "C:\Python26\lib\site-packages\sqlalchemy\pool.py", line 138, in
> create_connection
> return _ConnectionRecord(self)
> File "C:\Python26\lib\site-packages\sqlalchemy\pool.py", line 218, in
> __init__
> l.first_connect(self.connection, self)
> File "C:\Python26\lib\site-packages\sqlalchemy\engine\strategies.py", line
> 145, in first_connect
> dialect.initialize(c)
> File "C:\Python26\lib\site-packages\sqlalchemy\dialects\mysql\base.py", line
> 1774, in initialize
> default.DefaultDialect.initialize(self, connection)
> File "C:\Python26\lib\site-packages\sqlalchemy\engine\default.py", line 144,
> in initialize
> self._get_default_schema_name(connection)
> File "C:\Python26\lib\site-packages\sqlalchemy\dialects\mysql\base.py", line
> 1739, in _get_default_schema_name
> return connection.execute('SELECT DATABASE()').scalar()
> File "C:\Python26\lib\site-packages\sqlalchemy\engine\base.py", line 1157,
> in execute
> params)
> File "C:\Python26\lib\site-packages\sqlalchemy\engine\base.py", line 1252,
> in _execute_text
> parameters=parameters)
> File "C:\Python26\lib\site-packages\sqlalchemy\engine\base.py", line 1348,
> in __create_execution_context
> None, None)
> File "C:\Python26\lib\site-packages\sqlalchemy\engine\base.py", line 1311,
> in _handle_dbapi_exception
> self.invalidate(e)
> File "C:\Python26\lib\site-packages\sqlalchemy\engine\base.py", line 961, in
> invalidate
> if self.__connection.is_valid:
> AttributeError: 'MySQL' object has no attribute 'is_valid'
>
> I have spent a significant amount of time on this, and nothing makes sense.
> I've run the unittest.py code that comes with the connector, and (connecting
> to the same DB) ran the tests with success. Firstly, it would appear that
> there is a possible bug in base.py at line 962 where it asks " if
> self.__connection.is_valid:" as this attribute has not been created yet, and
> is conditionally created.
__connection is created in the constructor, and it may get del'ed by close or
invalidate. There's a check for closed right there, so its only if
invalidate() is called twice that there'd be an issue. But that's not what's
happening here, since __connection is present.
Its still a bug on our part though, partially, there's an edge case where the
__connection member is not the usual ConnectionFairy wrapper we use, and is the
raw DBAPI connection, and that is during the initilization phase of a new
connection. In your stack trace, a new connection is acquired from the DBAPI,
and we're calling "SELECT DATABASE()" on it. That is failing. Very
unusually, it is failing with an exception that passes the "is_disconnect"
test, which means the errno is in (2006, 2013, 2014, 2045, 2055, 2048)
according to the mysqlconnector dialect, and means the connection has been
lost. Interestingly, that is one more code than we have in base.py. So that
list of codes is suspect (the myconnpy guys provided some of this code) - the
base list used by the other MySQL dialects is (2006, 2013, 2014, 2045, 2055).
The exception then passes off to invalidate() which wasn't expecting a raw
DBAPI connection and it breaks. Ticket #1894 is added.
For the immediate issue you'd need to figure out what error SELECT DATABASE()
is returning.
> However, this is not the root of the issue, merely a distraction. (I forced
> this to exist and have a value, but the problem just fell through to further
> down the code)
>
> I can get this error by simply doing this (now) when this all has worked for
> days.
>
> e = create_engine('mysql+mysqlconnector://user:passw...@127.0.0.1/testdb',
> encoding='utf8', echo=False)
> e.connect()
>
> Any clues - as this is driving me nuts! Can't do ANYTHING now because I an
> no longer connect to the DB. DB manager and other tools all show MySQL
> happily ticking along. I have rebooted the server.
>
> As a possible solution, are there any other stable MySQL connectors out there
> that are easy to install on a Windows platform? The Python Connector one
> chosen has been good so far, but if that turns out to be the issue - it's
> gone!
>
> Cheers
> Warwick
>
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