New Relic supports Ruby on Rails 2.1 through 4.x
Time ERB and Haml templates
Transaction traces and web transaction breakdowns give you a detailed look into where your application is spending time. We automatically measure the render time of ERB and Haml templates as well as expose bottlenecks like slow queries that are getting triggered from within your views.
Automatic capture of SQL queries
In addition to counting and timing how many calls your Rails app makes to the database, New Relic will automatically capture slow queries and report the underlying database's query analysis. This functionality makes it easy to find that missing index and see any improvements it makes. We provide full support for ActiveRecord, DataMapper and Sequel. This means that getting deep insight into your application's database, tracking usage and performance is as simple as adding New Relic to your Gemfile.
Easy reporting of queue time
A common question among Rails developers is "how many application processes do I need to handle my traffic?" With New Relic, it’s easy to report "Queue time.” This feature shows you how long your front-end web server is waiting for a Rails process to become available. This reporting will happen automatically on popular Ruby platforms like Heroku and is trivial to configure in Nginx, Apache, and nearly any front-end web server. New Relic also provides a variety of capacity reports that will visualize how response time and throughput are related, as well as help you scale.