Adding more metrics such as cache hit/miss

[shouichi]

Hi,

ActiveSupport publishes bunch of events and we want to instrument cache hit/miss through cache_read.active_support.

https://guides.rubyonrails.org/active_support_instrumentation.html

General question: we ultimately can instrument all events published by active support but maybe it's too much. Where should we draw a line?

Thank you.

[Envek]

I don't think that it would be useful to subscribe to all possible things from ActiveSupport.

But for things that would be useful to many users pull requests are definitely welcome!