Global variables in Python and Apache mod_wsgi

Question

I know there are frameworks that exist, but I am trying to use wsgi directly to improve my own understanding.

I have my wsgi handler, and up at the top I have declared a variable i = 0.

In my application(environ, start_response) function, I declare global i, then I increment i whenever a button is pressed.

It is my understanding that the state of this variable is preserved as long as the server is running, so all users of the web app see the same i.

If I declare i inside the application function, then the value of i resets to 0 any time a request is made.

I'm wondering, how do you preserve i between a single user's requests, but not have it preserved across different users' sessions? So, a single user can make multiple posts, and i will increment, but if another user visits the web app, they start with i=0.

And I know you could store i in a database between posts, but is it possible to just keep i in memory between posts?

For some related background reading, look at code.google.com/p/modwsgi/wiki/ProcessesAndThreading The more relevant parts are towards end, but still important to read the rest for context. — Graham Dumpleton
– Graham Dumpleton, Commented Mar 2, 2012 at 22:49

Tobu · Accepted Answer · 2012-03-02 22:45:21Z

3

Web-apps are generally “shared-nothing”. In the context of WSGI, that means you have no idea how many times your application (and the counter with it) will be instantiated; that choice is up to the WSGI server which acts as your app's container.

If you want some notion of user sessions, you have to implement it explicitly, typically on top of cookies. If you want persistence, you need a component that explicitly supports it; that can be a shared database, or it can piggy-back on your cookie sessions.

answered Mar 2, 2012 at 22:45

Tobu

25.6k4 gold badges94 silver badges100 bronze badges

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

Comments

Ignacio Vazquez-Abrams · Accepted Answer · 2012-03-02 22:48:22Z

1

Add WSGI session middleware and store the value these.

answered Mar 2, 2012 at 22:48

Ignacio Vazquez-Abrams

804k160 gold badges1.4k silver badges1.4k bronze badges

Collectives™ on Stack Overflow

Global variables in Python and Apache mod_wsgi

2 Answers 2

Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related