Selective caching - by user

Question

Is it even possible to do this?

The goal is to group our visitors:

Group A sees Theme A
Group B sees Theme B

I am able to achieve this goal through cookies. But when caching is enabled (i.e. Site config > Performance > On), things are messed up. This is what happens:

1) Group A visits Page-1
-- Page-1 is not cached yet.
-- Cookies are properly checked.
-- Page-1 is displayed using Theme A

2) Group B visits Page-2
-- Page-2 is not yet cached.
-- Cookies are properly checked.
-- Page-2 is displayed using Theme B

3) Group A visits Page-2
-- Page-2 is already cached.
-- Cookies are ignored
-- Page-2 is displayed using Theme B (when it should be displayed using Theme A)

So now what I am thinking is, instead of using cookies, I'll use separate cache for each group.

Is this even possible? :S If not, any recommendations are welcome.

Inputs will be highly appreciated. Thanks!

Answer 1

Checkout Cache page based on cookie value and URL

Long story short what you want can be done. Depends on how you want to do it :)

Answer 2

Ok so here's what I did.

I extended drupal's cache.inc by including this line on settings.php

$conf['cache_inc'] = sites/all/modules/mycustom_module/my_custom_cache.inc';

I basically copied drupal's cache.inc and pasted it in my module's folder, renamed it, and then added a few lines of code where I altered how $cid's are generated. This way I am able to create $cid variants of cache depending on the theme