Python mod_wsgi application strange behavior

Question

I am relatively new to Python and Python web application development. Currently I am creating a hello world application in Python using mod_wsgi

Here are my configurations.

Apache configuration

<VirtualHost *:80>
    ServerName mysite.com
    DocumentRoot /var/www/mysite

    WSGIDaemonProcess mysite threads=5
    WSGIScriptAlias / /var/www/mysite/mysite.wsgi
    WSGIProcessGroup mysite

    <Directory /var/www/mysite>
        WSGIProcessGroup mysite
        WSGIApplicationGroup %{GLOBAL}
        Order deny,allow
        Allow from all
    </Directory>
</VirtualHost>

mysite.wsgi

import os
import sys

path='/var/www/mysite'
if path not in sys.path:
    sys.path.append(path)

import mysite.app

application = mysite.app.App()

app.py

import mysite.log as log

logger = log.custom_logger('root')
logger.debug('I am included only once')

class App:

    """ 
    This Class is responsible
    """  
    def __init__(self):
        logger.debug('I will be called only after apache restart')          

    """
    WSGI module will call this function by default    
    """
    def __call__(self, environ, start_response):
        logger.debug('I will be invoked for every request')    

        # Do some stuff here
        start_response(response_state, response_header)          
        return [response]

Problem: I am not able to see logs inside __init__ and log which is outside in app.py.

Output

First time run after restarting apache

DEBUG - app - I am included only once

DEBUG - app - I will be called only after apache restart

DEBUG - app - I will be invoked for every request

When I refresh the page in browser

DEBUG - app - I will be invoked for every request

What is happening? I am aware that __init__ is not constructor, application objects are caching somewhere? whats the story.

Just pointing, did you notice that the class name is App and you're instantiating APP? — Bibhas Debnath
– Bibhas Debnath, Commented May 8, 2013 at 4:44

Graham Dumpleton · Accepted Answer · 2013-05-08 04:45:06Z

2

Your code doesn't even match the messages logged.

Ignoring that, the module is imported only once when it is first loaded.

The __init__() is called only once when:

application = mysite.app.APP()

runs at the time of import. The __call__() is then run on every request.

So yes, stuff is cached within a process and is reused on subsequent requests.

IOW, things are not reloaded on every request like PHP.

So not sure what the problem is.

answered May 8, 2013 at 4:45

Graham Dumpleton

58.7k6 gold badges128 silver badges142 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Maddy Over a year ago

Thanks, I have just updated the logs, I am new to python, not sure how it will render.

Collectives™ on Stack Overflow

Python mod_wsgi application strange behavior

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related