Rails 4 multitencancy with subdomain login management - ruby-on-rails

Question

Scenario: Multi-tenant rails app that uses subdomains and devise
Problem: I want the user to be able to log into mydomain.com then be forwarded to their own subdomain1.mydomain.com address as a logged-in user. Right now they can only log directly into their own subdomain.
I'm a relative Rails newbie and I can't find a simple solution (although it seems like there must be one). Ideally I would like to have mydomain.com and subdomain1.mydomain.com share one cookie, but my skills aren't there for writing custom middleware. Obviously since it's multitenant I can't share one session across all subdomains. Stuck on this for a few days and curious if there is a simple solution (such as a config.session_store domain setting) that I'm missing before I start looking at OAuth or other more cumbersome solutions. Any help will be appreciated!
Edit: Of course I only found this after posting. Log a user into their subdomain after registration with Rails and Devise . Will try the config.session_store domain: :all with a before filter recommendation and post any details if it doesn't work, seems like a good idea at least.
Edit: SOLUTION that worked for my particular Devise with subdomains setup:
class ApplicationController < ActionController::Base
before_action :check_subdomain
def check_subdomain
unless request.subdomain == "" or request.subdomain == session[:subdomain]
redirect_to request.protocol+request.domain
end
end
end
session_store.rb
My::Application.config.session_store :cookie_store, key: '_my_session' , :domain => :all, :tld_length => 2
Basically I set the subdomain in the session with session[:subdomain] at login and use that to scope the session to the current user. Otherwise when the domain is set to :all in session_store it breaks the scope. If the user is not authorized it redirects them to the public home page via the request.protocol (http:// or https://) +request.domain redirect. Simple! Now users can move between the base domain and their subdomain within the same session.

Answer 1

Cookie
From what you've posted, I'd estimate you have a problem with the tracking of your session cookie. We had a similar problem with our subdomain-powered application, which lead to the cookie being dropped each time you switched between the two
We found the remedy here:
Share session (cookies) between subdomains in Rails?
#config/initializers/session_store.rb
Your_App::Application.config.session_store :cookie_store, key: '_your_app_session', domain: :all, tld_length: 2
The trick is the tld_length argument - this allows you to define how many "levels" of the domain can be accommodated; IE if you're using a sub domain, you'll need to set the tld_length to reflect it
Forwarding
I'm not sure whether you have a problem with your forwarding or not; I'll give you some ideas anyway.
When you log into a "subdomain", unless you've got a true multi-tenancy implementation of Rails (where each user is stored in a different database), you should be able to allow the users to login on the main form, and then redirect them to the subdomain without an issue
Something you need to consider is the subdomain constraint will only be populated if you use _url path helpers:
<%= link_to "Your Name", path_url(subdomain: "subdomain_1") %>
The reason for this is the _path helper is relative to the base URL, and consequently cannot populate the subdomain option. Alternatively, the _url path helper points to the URL in its entirety -- allowing you to define the sub domain as required
--
If you send the request & continue to want the user to remain signed-in, you'll need to ensure you're able to persist the authentication across the sub-domains. IE if you have a single-sign in form on the "main" page, you'll want to ensure you can continue the authentication into the subdomains