Configuring Rails App to handle multiple domains and multiple cookies

I have a rails app which supports multiple domains and each domain may
have multiple subdomains.

Users visiting do not receive the same experience as (although the base behaviour of the apps is the same)

Therefore, if a user is logged in to, it shouldn’t then
be logged in to

If a user is logged in to, it should then be
logged in to

Previously, I’ve handled this by setting the domain in the session
store configs:

MyApp::Application.config.session_store :cookie_store, :key =>
‘_MyApp_session’, :domain => APP_CONFIG[:domain]

I’m trying to work out the best way to handle this with multiple

I’ve tried hacking around ActionDispatch::Callback but the request is
not available from within there.

Can anybody suggest a good way of supporting multiple cookies from
within one app?

Ideally I’d like to create a fresh cookie for each domain.