How do I share some session variables across Django Subdomain sessions
It depends on how you are persisting your sessions. If you are using cookies to persist your sessions which seems likely, and you aren't willing to use a .site.com cookie domain, then you need to offload your session storage to something like Redis or some other key/store sort of server agnostic option.
I have a Django app that has wildcard subdomains. The user has multiple login sessions across these subdomains. For example, he goes to sd1.site.com and logs in(HTTP POST request to sd1.site.com/login/)  with credentials username1 and password1. This creates a session for the user on sd1.site.com. He then goes to sd2.site.com and logs in with credentials username2 and password2. This creates a session for the user on sd2.site.com.
My end goal is to tell sd1.site.com that the user is logged in from sd2.site.com as well. My plan is to store a session variable called 'domains_logged_in' with value ['sd1','sd2']. Both sd1 and sd2 should be able to access 'domains_logged_in'.
Setting SESSION_COOKIE_DOMAIN = '.site.com' is not an option as it makes it difficult to manage multiple sessions and is not entirely secure. Am I missing something?