RailsMetrics is an engine that hooks into your application to listen ActiveSupport::Notifications and show you statistics about them. RailsMetrics uses threads to save those notifications in the database through an in-process Queue. You can see charts based on each request and see what queries, actions, templates rendering, etc. are slow.

So far RailsMetrics supports only ActiveRecord as ORM but adding other datastore should be easy (take a look at lib/rails_metrics/orm/active_record.rb). Due to the threaded behavior in RailsMetrics, you cannot use SQLite as database, however MySQL and PostgreSQL work fine.

There’s an example application at github.com/engineyard/rails_metrics_example .