The controller runtime stats integration always reports 0ms. This is due to a mixup between mongo-ruby and Rails and how they measure time.

Specifically, Rails (and ActiveSupport) assume that event.duration is in milliseconds. However, mongo-ruby produces events with .duration in seconds.

What actually happens:

Completed 200 OK in 7ms (Views: 0.1ms | MongoDB: 0.0ms | Allocations: 2345)

What should happen:

Completed 200 OK in 7ms (Views: 0.1ms | MongoDB: 1.9ms | Allocations: 2345)

Possible fixes:

1) in railties/controller_runtime.rb, change line 63:

def _completed e
  Collector.runtime += e.duration * 1000
end

This simply converts inbound seconds to milliseconds so that the value is rendered properly in log_process_action() (line 44).

2) Make event.duration conform to the ActiveSupport spec by converting everything to ms. This would make it easier to add custom logging subscribers to mongo-ruby events. Presently all subscribers would have to *1000 just like the default subscriber mentioned in (1).

This is, of course, a much farther reaching change, so perhaps (1) is more appropriate, especially for a patch release.