emlynj at gmail.com
Sun Jun 25 20:34:53 EDT 2006
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.