The idea is to turn it on for a given request when needed - via a parameter, feature flag, etc. prepend_around_action :callstacking_setup, if: -> { params[:deb

The idea is to turn it on for a given request when needed - via a parameter, feature flag, etc. prepend_around_action :callstacking_setup, if: -> { params[:debug] == '1' } Once the request completes, the instrumented methods are removed to remove the performance overhead.