[mod_python] Session management

Please don't put sess in global scope as Manfred Stienstra mentioned 
previously. That scope is module scope, one in one interpreter.

Every function that use session would be like this:

def func(req):
	sess=Session(req) # you always need this line.
	sess.load()
	# do something
	sess.save()
	return "something"

The problem you encountered was:
- send request to httpd
- new python interpreter is created (httpd child process 
  is creatated)
- your python module for Publisher Handler loaded.
- call otherFunc at the first time.
- if you drop "sess=Session(req)", sess.load() is passed, which means
  NoneType type ojbect method call.


> Hmm... the session object is still dropping (being lost) , the
> recovered (being remember) from time to time.
> 
> Brief view of the Publisher Handler setup.
> *Note the sess variable is not visible to other functions unless
> declared globally.
> 
> [Global Space]
> sess = None
> 
> def login(req):
>    global sess
>    sess = Session(req)
>    sess['this']  = 'that'
>    ...<more code>...
>    sess.save()
>    return
> 
> def otherFunc(req):
>     global sess
>     sess = Session(req)  # tested with and without this line (correct?)
>     sess.load()
>     ...<more code>...
>     sess.save()
>     return
> 
> I can see the session being written to a file in a serialized way in /tmp
>     mp_sess.dbm.bak
>     mp_sess.dbm.dat
>     mp_sess.dbm.dir
> 
> I've also executed a:
> 
>     watch -d 'ls -l /tmp/mp*'
> 
> And upon creating new sessions...via separate browsers... I have seen the file
> size fo the above files grow in real-time, which means that data is in
> fact being added to the sessions which are partly human-readable.
> 
> However, the problem I'm having is that occasionally when
> transitioning to other pages such as http://mysite.com/otherFunc,
> 
> will return 'NoneType' object has no attribute 'load'  # referring to
> the sess object.
> 
> So I click the [BACK] button in the browser and re-submit the data. 
> After about 7 times, the script all of a sudden recognizes the sess
> object.  Sometimes this error does not happend and loads on the first
> try. How can I prevent this behavior?
> 
> ~= Chris =~
> 
> 
> On Wed, 12 Jan 2005 23:48:39 +0900, Hiroaki KAWAI <kawai at iij.ad.jp> wrote:
> > Of cource, most popular and easiest way is to use Session module.
> > Session will store the information somewhere in 'session storage' that
> > the module knows how to get it, and the actual mechanism is hidden.
> > # i.e., inter-process communication via file or database.
> > 
> > So, make sure that you save the session information to the session
> > storage in each request processing as Ron says. ;-)
> > 
> > 
> > Chris Jackson <christopher.jackson at gmail.com> wrote:
> > > Ah, that makes sense...Now I just need to find which "inter-process"
> > > technique I should be using in order to maintain consistency ;)
> > >
> > > ~= Chris =~
> > >
> > >
> > > On Wed, 12 Jan 2005 12:55:47 +0900, Hiroaki KAWAI <kawai at iij.ad.jp> wrote:
> > > > > > Depending on what type of apache configuration you run, one or more
> > > > > > interpreters will be used. Sometimes interpreters die and new ones get
> > > > > > created.
> > > > >
> > > > > Hmm...it's interesting you say that somtimes the interpreters die and
> > > > > new ones get created because I'm running into a "problem" where I will
> > > > > test a mod_python page and it will works perfectly several times again
> > > > > and again, but then i'll test it out again, and the interpreter seems
> > > > > to "forget" the values.  I'll keep testing the page with the same
> > > > > values, and then the page will work again.
> > > >
> > > > One interpreter is created per one apache child process. If you're running
> > > > prefork MPM (and set MaxRequestsPerChild or have multiple spare child
> > > > servers), you're posting a HTTP request sometimes to the same interpreter,
> > > > sometimes to other interpreter.
> > > > I think one of 'inter-process' techniques is useful for what you're
> > > > trying.
> > > > # If I'm saying wrong, someone please correct. :-)
> > > >
> > > > ---Hiroaki Kawai
> > > >
> > > > _______________________________________________
> > > > Mod_python mailing list
> > > > Mod_python at modpython.org
> > > > http://mailman.modpython.org/mailman/listinfo/mod_python
> > > >
> > 
> > ---Hiroaki Kawai
> > 
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> >