[mod_python] Session Hanging Problems

David Janes davidjanes at blogmatrix.com
Mon Nov 26 13:55:39 EST 2007

All I can say is "we too" -- we're using FileSession. We have not been
able to come up with a cure, though we've minimized use of sessions
which brings the frequency down significantly.

Regards, etc...

On Nov 26, 2007 1:39 PM, Harish Agarwal <harish at octopart.com> wrote:
> I'm using session handling with ModPython 3.3.1.  Originally I was
> using DbmSession and have since transitioned to a custom MySQL Session
> handler.  With both session types, however, I've noticed that session
> initialization intermittently hangs (not forever, but takes as long as
> four minutes to complete), at a low-ish (a handful of times every
> hour, while receiving, say, on order of a thousand or so requests
> every hour) frequency which seems to scale with the amount of traffic
> we're receiving.  I had read that long DbmSession cleanups can cause
> problems, which is why I transitioned to the MySQL system, which takes
> < 1 second to complete, but I'm still noticing the long session init
> times.
> I put some debugging statements into the code and it seems to be
> related to session locking.  In particular, it is this function call
> in the lock method of the BaseSession class:
> _apache._global_lock(self._req.server, self._sid)
> which is taking some time to complete. I'm not familiar with
> _apache._global_lock (is it used to apply a mutex lock to the
> session?) and am having trouble finding information describing its
> usage - but it seems likely that this is the root cause.  In the past
> I've had problems with session locking but have since transitioned the
> code to ensure that only one session is created per request, as such:
> if not hasattr(req,'session'):
>              req.session = Session.MySQLSession(req)
> Can anyone tell me if this kind of behavior is normal or is indicative
> of some common configuration or coding error?  Any help would be
> greatly appreciated.
> Thanks,
> -Harish
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David Janes
Founder, BlogMatrix

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