Our application at Yardstick is Rails 2.3.x, and we use some Sinatra based metal controllers. We also use NewRelic to monitor things. Get Low Something got updated somewhere, maybe the NewRelic gem, maybe something else. Our Apdex hit 0.3 or something stupid and stayed there. After a long debugging period going back and forth with the NewRelic folks, we figured it out. Problem, meet Solution The way a metal controller in Rails 2.3 works is that …