Per default Symfony2 will store session information in its cache directory. Clearing the cache thus logs everyone out.
A simple solution to this is moving where Symfony saves its sessions. We can do this by configuring the framework bundle via our app/config/config.yml.
framework:
session:
save_path: %kernel.root_dir%/var/sessions
That one line save_path setting will redirect session data to app/var/sessions. Problem solved!
If you are also using Capifony (and you should!) then remember to share the sessions between releases, in your deploy.rb.
set :shared_children, [app_path + "/var"]