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CGI deployment on Apache

Here are the simple steps needed to create and run an web.py application.

  • Install web.py and flups

  • Create the application as documented

      if __name__ == "__main__":
          web.application(urls, globals()).run()

For our example, let it be named app.py, located in /www/app and we need it accessible as http://server/app/app.py.

  • Configure Apache (version 2.2 in this example)

      ScriptAlias /app "/www/app/"
      <Directory "/www/app/">
              Options +ExecCGI +FollowSymLinks
              Order allow,deny
              Allow from all

That’s it. Your application is accessible via http://server/app/app.py/. Additional URLs handled by the application are added to the end of the URL, for examples http://server/app/app.py/myurl.

  • .htaccess configuration

            Options +ExecCGI
            AddHandler cgi-script .py
            DirectoryIndex index.py
            <IfModule mod_rewrite.c>
                RewriteEngine on
                RewriteBase /
                RewriteCond %{REQUEST_FILENAME} !-f
                RewriteCond %{REQUEST_FILENAME} !-d
                RewriteCond %{REQUEST_URI} !^/favicon.ico$
                RewriteCond %{REQUEST_URI} !^(/.*)+index.py/
                RewriteRule ^(.*)$ index.py/$1 [PT]

Here it is assumed that your application is called index.py. The above htaccess checks if some static file/directory exists failing which it routes the data to your index.py. Change the Rewrite Base to a sub-directory if needed.

#Hiding the script name using mod_rewrite (tested with webpy 0.33)

(warning: this section written by someone new to webpy; it works, but may not follow prescribed practices)

If you want your app accessible as http://server/app/ and not http://server/app/app.py/ (i.e. http://server/app/articles/ and not http://server/app/app.py/articles) then you need to tweak mod_rewrite a bit. Here’s an example of the relevant bit in a .htaccess file (placed in /www/app or wherever app.py is):

RewriteEngine on
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^(.*)$ app.py/$1 [L]

It’s cruder than the rewrite rules presented above. The first rule states that if a file exists it should be served by the webserver (ideally you’d want something more secure than that, like only certain file types, or only static/). The second line says in any request of form .../app.py/blah we should run app.py and give it blah.

So now if you go to http://server/app/ you’ll hit app.py’s handler for '/'. If you go to http://server/app/articles, the handler for '/articles', etc.

Are we done? Well, that’s what I thought. There’s still one problem: webpy doesn’t know how things were rewritten on the way in, so it doesn’t know how to rewrite them on the way out.

For instance, one can normally use web.url() to compose urls such that the right content is found. Want static/style.css? Call web.url('/static/style.css') and you'll get ... /app/app.py/static/style.css` … not what we wanted. That doesn’t exist. Problem.

If you don’t use web.url(), it can still bite you because webpy does. Say raise web.seeother('/') and you’ll end up at http://server/app/app.py/, which defeats the purpose of hiding it using mod_rewrite.

How to fix that prefix on the way out then? That’s stored in web.ctx.homepath. Unfortunately, efforts to modify that didn’t work for me. Some old forum post said it comes from the environment variable SCRIPT_NAME but that didn’t work either. It turns out REAL_SCRIPT_NAME works though, so we can add the following to our app.py, before initialising webpy:

import os

home = '/app'
os.environ["SCRIPT_NAME"] = home
os.environ["REAL_SCRIPT_NAME"] = home

#and calling web.application or whatever goes here or after

This seems to work. Running raise web.seeother('/') gets us to http://server/app/ like we wanted.