Rails authenticate mongodb_logger with devise

I've got installed gems mongodb_logger and devise.
I was wondering how to restrict access to users who are registered in devise ?
I tried as follows( restricting to users with admin role)

authenticate :user, ->(u) { u.admin? } do
mount MongodbLogger::Server.new, at: "/mongodb_logger", as: :mongodb_logger,

in my routes.rb. But this didn't help... How can I do such a thing ?