[mod_python] Questions for the FAQ - please check and confirm (req.write() and return) also docs update ...

vio vmilitaru at sympatico.ca
Fri Aug 16 15:58:59 EST 2002

* Mateusz Korniak <mateusz at ant.gliwice.pl> [020816 15:26]:
> On Friday 16 August 2002 21:47, vio wrote:
> > Same here. My handler builds dynamic pages using successive calls to
> > req.write() with no problems. In fact, the only issue here might rather be
> > whether it is better (as in 'less expensive') to 'assemble' the document in
> > memory and send it in one swoop to the client, as opposed to sending it
> > in many calls to req.write().
> > In other words, whether it's preferable to assemble a dynamic document at
> > the server level, or at the client level. I would tend to believe
> > the former is better, because it reduces network traffic. Though I could be
> > mistaking. But mod_python definitely allows both strategies.
> >
> Yes. But what in publisher handler case ?
> Can you use req.write() instead of returning page ?
> I get Internal server error in that case ... :(

I don't quite understand your question. req.write() IS the returning page.
But I think I know where the bobo is: it's the Internal server error message.

Try the following:
I am assuming you are using the out-of-the-box publisher. I suspect the problem
is not necessarily the 'req.write(), calls, so I suggest you try the following
debugging technique to find out your 'real' bug (you will have to modify the 
publisher.py like following):

somewhere before beginning of the handler() routine, add:
# debugging LOG file - use this instead of '_REQUEST.write()' for debugging
LOG = open('/path/to/.../LOG', "a")

then, find each line in publisher.py:

and modify it like this:
LOG.write('line ...\n') # current line number in publisher.py

This will help you pinpoint exactly who/what throws that Server Error message.
(just read the LOG file). Then work your way from there. I bet your problem
is not your req.write() calls, but something you don't even expect.

Debugging mod_python scripts is tricky, because you can not always write 
debugging messages to the browser. My solution is to use a LOG file.

Hope this helps. (It sure helped me a lot this far).

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