[Tutor] cgi, fastcgi, mod_python

[Lloyd Kvam]

On Thu, 2004-04-29 at 15:36, Mike Hansen wrote:
> Hello,
> 
> I've recently started experimenting with Python to write web apps. My 
> first app did a little form processing using the cgi module. Performance 
> isn't a huge issue, but I'm curious on how to pep it up if the need 
> should arise. I'm a bit confused on other solutions like FastCGI and 
> Mod_Python. If I decided to use FastCGI, would I need to significantly 
> change my code? 

The main impetus for using fastCGI or Mod_Python is to avoid starting a
whole new process for each HTTP transaction.  This becomes an issue on
very high traffic sites OR where your script needs to go through
elaborate initialization routines.  The jonpy module (from sourceforge)
can simplify a fastCGI script.  Jonpy provides a different interface to
the parameters and environment as compared to the cgi module.  However,
it is easy to feed the jonpy parameters into the cgi module so that most
of a fastCGI script is similar to a regular cgi script.  Only the
"startup logic" needs to be different.  In a simple case, the startup
logic is the call to cgi.fieldstorage which gets replaced by a jonpy
cgihandler class which accepts the jonpy parameter objects.  These can
be fed to cgi.fieldstorage.  Make the rest of the cgi script into a
function that gets the cgi.fieldstorage object as a parameter.  (I hope
that made sense.)

I have found that most web sites will work quite nicely through the
regular cgi interface.  Even establishing database connections each time
the script is run normally works OK.

The jonpy module provides a simple set of tools to handle the creation
and re-use of resources such as database connections.

> I didn't get the impression that you just install it, 
> modify your apache config, and import FastCGI in your code instead of 
> the cgi module. The same with Mod_Python. Could someone briefly explain 
> the differences in coding cgi, FastCGI, or Mod_Python if there are any 
> differences?

fastCGI and Mod_python require more configuration of the web (apache)
server.  Mod_python allows for much tighter integration with the apache
server.  Each HTTP request goes through a series of steps within
apache.  Mod_python gives you the means to add scripting at each step.  

I have NOT done any mod_python scripting.  I have not found fastCGI to
be necessary.  I keep a test server configured so that I can run fastCGI
scripts and I practiced converting a couple of cgi scripts to fastCGI. 
It was NEVER necessary to actually deploy a fastCGI script into
production.

> 
> Thanks,
> 
> Mike Hansen
> 
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Lloyd Kvam
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