[mod_python] MySQL Session implementation?

Sébastien Arnaud arnaudsj at emedialibrary.org
Tue Jun 20 23:19:56 EDT 2006

Hi Nicolas,

Thank you for all the pointers. I have already cooked a fairly simple  
connection pool in my own baked framework which I use mostly now when  
developing for mod_python. Graham had helped me a while back to try  
to get it right, so as soon as I have a chance to write a draft of a  
MySQLSession module, I'll try to make it work with connection pooling  
and post it to the list for review.

Thanks again.


On Jun 20, 2006, at 2:37 PM, Nicolas Lehuen wrote:

> 2006/6/20, Sébastien Arnaud <arnaudsj at emedialibrary.org>:
>> Thanks Jim, it looks like SQLiteSession is a good start for what I
>> want to do.
>> If I am successful I will share with everybody whatever I come up  
>> with.
>> Thanks!
>> Sébastien
> Hi Sébastien,
> One important thing not to overlook if you are going to implement a
> MySQLSession class is database connection pooling.
> In SQLiteSession, I deliberately did not handle this issue because it
> is written in the documentation that connections created in a thread
> should not be reused in another thread (see
> http://www.sqlite.org/cvstrac/wiki?p=MultiThreading : "# On some
> operating systems, a database connection should always be used in the
> same thread in which it was originally created. ").
> As a result, each and every session load or saved forces a database
> connection, which means opening files, reading data structures
> (indexes and tables) and syncing them when the connection is closed.
> No wonder then that SQLiteSession is slower than FileSession...
> As a minimum effort, I could have used thread local variables to make
> sure that only one connection is opened by thread, but thread local
> variables are a Python 2.4 feature and we need to support Python 2.3.
> So I've just let it as is for the moment, since anyway we decided to
> put this code in the sandbox until better times.
> With MySQL or other DBMS, however, connection pooling can and should
> be used for better performances. Writing a connection pool is not very
> difficult, but writing it in a stable and resilient way, both
> thread-safe and multi-process safe, is a little bit more effort.
> One thing to consider is to try to build the connection pool and the
> session management code in two different, orthogonal modules, so that
> one day we'll be able to release the connection pool for general
> purpose.
> Regards,
> Nicolas

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