New Relic is a performance management system, developed by New Relic, Inc (http://www.newrelic.com). New Relic provides you with deep information about the performance of your web application as it runs in production. The New Relic Ruby Agent is dual-purposed as a either a Gem or plugin, hosted ...

Provides a better error page for Rails and other Rack apps. Includes source code inspection, a live REPL and local/instance variable inspection for all stack frames.

help to kill N+1 queries and unused eager loading.

Supporting gem for Rails Panel (Google Chrome extension for Rails development)

Monitors Ruby apps and reports detailed metrics on performance to Scout.

The official appsignal.com gem

An experimental metrics client.

Take a peek into your Rails application.

Collect statistics about how your application is performing with ease. Export metrics to various monitoring systems.

Every Rails page has footnotes that gives information about your application and links back to your editor.

Collect high level application performance metrics and forward them for analysis

The friendly gem that instruments everything for you, like I would if I could.

This framework lets you build & easily layout dashboards with your own custom widgets. Use it to make a status boards for your ops team, or use it to track signups, conversion rates, or whatever else metrics you'd like to see in one spot. Included with the framework are ready-made widgets for...

Automatic tracing and metrics for Ruby applications. Get started at appoptics.com. @AppOptics

FnordMetric is a Ruby Event-Tracking gem on steroids

Gem to make statistics sending from Ruby applications simple and efficient as possible. Currently supports Statsd, and is inspired by the original ruby-statsd gem by Etsy.

With query_trace enabled, the Rails logs will contain a partial stack trace for every executed SQL statement, making it easier to find where they are generated in your code.

Debugging toolbar for Rack applications implemented as middleware. Based on logical-insight and rack-bug.

The Rails View Annotator makes it easy to find out which partial generated which output

The exceptionally handsome dashboard framework for Rails.

Observe your web applications in the wild! == DESCRIPTION

Debugging toolbar for Rack applications implemented as middleware

Server for handling metrics from metriks

Gem to make statistics sending from Rails applications simple and efficient as possible

Metrics measurement for your app on top of ActiveSupport::Notifications

Middleware to show instrumentation information in http headers

Surface slow code paths in your Rails 3 app via Growl / libnotify

System Metrics is a Rails 3 Engine that provides a clean web interface to the performance metrics instrumented with ActiveSupport::Notifications