[mod_python] Checking a PSP-generated response before starting to send it..?

Hmmm, those search terms may not have helped much. Try:

  http://www.modpython.org/pipermail/mod_python/2005-May/018230.html

instead.

Have also logged an issued for adding proper way of doing this since
it does come up occasionally.

  https://issues.apache.org/jira/browse/MODPYTHON-236

Graham

On 29/06/07, Graham Dumpleton <graham.dumpleton at gmail.com> wrote:
> On 29/06/07, Aaron Robinson <aaron.robinson at mojoworld.com> wrote:
> >
> >
> >
> >
> > For lack of any feedback on this, I've come up with 1/2 a solution
> > (possibly), but would still very much appreciate *any* input..
> >
> >
> >
> > I've written a output filter which read()'s all the input it gets, then
> > stores it in an attribute it creates on filter.req (and write()'s nothing),
> > then when it reads None (end of stream) it can compare the total page to the
> > last sent page and either write() the whole page (unmodified) or change the
> > 'Last-Modified' date to the previous date + change the response code to a
> > 304...  problem is that I don't know if it's possible for an output filter
> > to change the response code..
> >
> >
> >
> > Any ideas on how to make an output filter change the response code, or
> > whether there are any holes in this plan - or preferably if there's a way to
> > avoid this completely?
>
> Can't be done.
>
> I'm a bit busy to respond in detail on this at the moment, but do a
> search through the mailing list archives using the search box on
> www.modpython.org for 'publisher PSP'. This should pick up messages
> which talk about using PSP from publisher, thus giving you more
> control. There has also been past discussions on how to make PSP
> output to a string so one can process output like you want. Look for
> 'PSP request wrapper'.
>
> Graham
>
> > Thanks,
> >
> > Aaron.
> >
> >
> >
> >  ________________________________
> >
> >
> > From: mod_python-bounces at modpython.org
> > [mailto:mod_python-bounces at modpython.org] On Behalf Of
> > Aaron Robinson
> >  Sent: Wednesday, 27 June 2007 11:28 p.m.
> >  To: mod_python at modpython.org
> >  Subject: [mod_python] Checking a PSP-generated response before starting to
> > send it..?
> >
> >
> >
> >
> > Hi all,
> >
> >
> >
> > I'm running Apache 2.2.4 on Win32 with mod_python 3.3.1 and Python 2.5.1.
> >
> > I'm completely new to Apache (and hence mod_python), but am reasonably
> > proficient with python itself.
> >
> >
> >
> > I'm working on a web service where all content is generated on the fly, and
> > am wanting to use PSP to facilitate this.
> >
> > Making as much use as possible of "304: Not Modified" is extremely important
> > to this project to reduce bandwidth, which is difficult as I have to
> > generate the content before I know whether it's different ("been modified")
> > from the last time I sent it or not..
> >
> >
> >
> > I previously used a mechanism (not using Apache) where I would generate the
> > response, then take a hash of it and if it matched the hash of the last
> > response I sent, I would instead send a "304: Not Modified".
> >
> > My problem is that when using PSP.run(), the response has already been sent
> > by the time it's finished being generated, so I have no opportunity to step
> > in and examine the response to see if sending a 304 is possible.
> >
> >
> >
> > I'm needing an across-the-board mechanism for dealing with this - I thought
> > of serializing the "vars" dictionary before passing it in and taking a hash
> > of that for comparison, but this is hardly full-proof, as it would
> > (incorrectly) lead to responding with a 304 even with different "session"
> > information, or, in the slightly odd case that the PSP file made use of
> > random.random(), etc.
> >
> >
> >
> > Just a thought: Is there a more general mechanism that can detect identical
> > content to a previous response on the way out and replace it with a 304?
> >
> >
> >
> > Thanks in advance,
> >
> > Aaron.
> > _______________________________________________
> > Mod_python mailing list
> > Mod_python at modpython.org
> > http://mailman.modpython.org/mailman/listinfo/mod_python
> >
> >
>