Debug Ruby Startup with Bumbler

If your Bundler-based application boots slowly, Bumbler provides insights into which gems are causing the delay.

Setup

Add gem 'bumbler' to your Gemfile and export the Ruby option in your shell config: export RUBYOPT=-rbumbler/go.

Analysis

When you boot Rails (e.g., rails c), you will see a progress bar. You can then list slow items: Bumbler::Stats.all_slow_items.

"Switching from Ruby 1.9.3 to Ruby 2.0.0 can significantly lower boot times for the same application".