generate_sid

# File actionpack/lib/action_dispatch/middleware/session/cache_store.rb, line 70
        def generate_sid
          if @check_collisions
            loop do
              sid = super
              key = cache_key(sid.private_id)
              break sid if @cache.write(key, {}, unless_exist: true, expires_in: default_options[:expire_after])
            end
          else
            super
          end
        end