A Ruby gem for detailed Rails application performance monitoring 📈. Metrics, errors and transaction traces are reported to Scout, a hosted application monitoring service. We have a free plan for small apps and a 14-day all-access trial to test out all the features. If you want to send us Rails logs, add our other gem and we will correlate them with your performance data!

The Scout agent is engineered to do some wonderful things:

• A unique focus on identifying those hard-to-investigate outliers like memory bloat, N+1s, and user-specific problems. See an example workflow.
• Low-overhead
• Production-Safe profiling of custom code via ScoutProf (BETA).

Add the gem to your Gemfile

gem 'scout_apm'

Add a version of the parser gem that supports your version of Ruby. For example, if you're on Ruby 3.3.0:

gem 'parser', '~> 3.3.0.0'

Update your Gemfile

bundle install

Signup for a Scout account and put the provided config file at RAILS_ROOT/config/scout_apm.yml.

Your config file should look like:

common: &defaults
  name: YOUR_APPLICATION_NAME
  key: YOUR_APPLICATION_KEY
  monitor: true
test:
  monitor: false
production:
  <<: *defaults

All of our accounts include Error Monitoring with 5000 errors/month free. To enable it, add the following to your scout_apm.yml:

# Common/dev/production/etc. whereever you would like to start trying it
# monitor: true should also be required to ensure your App exists in Scout
errors_enabled: true

To use DevTrace, our free, no-signup, in-browser development profiler:

1. Add the gem to your Gemfile:

# Gemfile
gem 'scout_apm'

2. Start your Rails app with the SCOUT_DEV_TRACE environment variable:

SCOUT_DEV_TRACE=true rails server

• Point your gemfile at your local checkout: gem 'scout_apm', path: '/path/to/scout_apm_ruby
• Compile native code: cd /path/to/scout_apm_ruby && bundle exec rake compile

For the complete list of supported frameworks, Rubies, configuration options and more, see our help site.

Email support@scoutapm.com if you need a hand.