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Emlyn Jones
emlynj at gmail.com
Mon Jun 26 10:58:22 EDT 2006
On 6/26/06, Emlyn Jones <emlynj at gmail.com> wrote: > On Monday 26 Jun 2006 01:13, Graham Dumpleton wrote: > > Emlyn Jones wrote .. > > > > > Hello, > > > I've got this simple piece of mod_python/psp; If I uncomment the > > > foo=session line I get a seg fault. Has anyone seen this before and can > > > direct me towards finding out what the problem is please? > > > I'm running Apache/2.0.50, mod_python 3.2.8 and Python 2.4. > > > I've confirmed that it isn't the known expat and mysql/php problems. > > > > > > <% > > > #foo = session > > > done_login = False > > > if(form.has_key("username")): > > > username = form["username"] > > > password = form["password"] > > > req.write("%s" % (username,)) > > > %> > > > > What PSP does is that if it sees that the variable "session" is referenced > > from inside of PSP code, then it will do what is necessary to create the > > session, or if the session already exists, it will retrieve it from the > > session database. > > > > Two problems could be occurring here. The first is that if this is > > occurring on the very first time the session needs to be created, that the > > session database it tries to use is corrupt in some way and therefore > > crashing. The second is that the session already exists in the database, > > but something was stored in the session object that probably shouldn't have > > and when the session object is being restored, it is triggering some code > > (possibly C code) which is then subsequently crashing. > > > > First thing you need to do is get out of PSP and write a simple handler > > that creates a session object just to validate that sessions work and that > > the session database is okay. Use a handler such as: > > > > from mod_python import Session > > from mod_python import apache > > > > def handler(req): > > session = Session.Session(req) > > session['data'] = 1 > > session.save() > > req.content_type = 'text/plain' > > req.write('hello') > > return apache .OK > > > > If this dies, then there is possibly a problem with the session > > database, or your Python DBM modules are stuffed somehow. You need to > > work out what type of session database is being used. It will probably > > be DBM database and it will be stored in "/tmp" as "/tmp/mp_sess.dbm". I > > am guessing you aren't on Win32 as in that case an in memory session > > database is being used and it would be almost impossible to crash. Which > > is might be is dictated by the MPM which Apache was configured with. > > > > Assuming it is DBM, check who owns the database in "/tmp". The owner > > should match the user that Apache runs as. If you have multiple versions > > of Apache running and they run as different users, you could have problems > > because of that. If it is the wrong user and you only have one Apache > > instance, you could try deleting the database and restarting Apache. > > If you have multiple versions of Apache running as different users, you > > may have to use PythonOption to change location where session database > > is stored. See documentation for mod_python. > > > > If this is all okay, may be what you are storing in the session object. > > This is where you need to show your code as to what you are sticking in the > > session object before we can really comment. Also read: > > > > http://www.dscpl.com.au/articles/modpython-005.html > > > > Graham > > Hi Graham, thanks for the reply and explanation. > That simple handler does die. The dbm file in /tmp checks out ok, it's the > correct user and I haven't actually managed to store anything in it yet. This > is the first use of it; In fact, If I rename it (the dbm file) and restart > apache it doesn't get recreated so I guess that leaves me with the python DBM > modules. > I'll have a dig around and see what I can come up with. > I do vaguely remember a caffeine fuelled evening running into problems with > sleepycat which sounds like it might be connected (maybe library versions?). > Is there any extra debugging info I can turn on to point me in the right > direction? Otherwise I suppose it's trying to test out the dbm stuff in a > python shell first and take it from there. > > Cheers, > Emlyn. > > _______________________________________________ > Mod_python mailing list > Mod_python at modpython.org > http://mailman.modpython.org/mailman/listinfo/mod_python > Hello, I'm not sure if I'm heading in the right direction here. I can see from a python shell that the dbm module is using the "Berkeley DB" library (dbm.library). lsof -p <http pid> | grep dbm shows that it is linked to libgdbm.so.3.0.0. I'm a little confused but could this be the root of my problems? Cheers, Emlyn. /usr/lib/libgdbm.so.3.0.0
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