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Speedup applications boot by caching require calls

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Build Status Gem Version

Speedup applications boot by caching file locations during require calls.

Speed gain depends on your number of gems. Under 100 gems you likely won't see the difference, but for bigger applications it can save 1 to 3 seconds of boot time per 100 used gems.


# Gemfile
gem 'bootscale', require: false


For correctness cache should be updated everytime $LOAD_PATH is modified by calling Bootscale.regenerate.

For Rails apps it means adding an initializer in config/application.rb.

module MyApp
  class Application < Rails::Application
    initializer :regenerate_require_cache, before: :load_environment_config do

Rails applications

Locate require 'bundler/setup' in config/boot.rb and add require 'bootscale/rails' after it:

require 'bundler/setup'
require 'bootscale/rails'

Other Bundler enabled applications

Locate require 'bundler/setup', and add require 'bootscale/setup' after it:

require 'bundler/setup'
require 'bootscale/setup'

Faster cache loading

In order to gain ~10-30ms of extra load speed, you can use the msgpack gem:

# Gemfile
gem 'msgpack',   require: false
gem 'bootscale', require: false
# config/boot.rb (or wherever you have the require of bundler/setup)
require 'bundler/setup'
require 'msgpack'
require 'bootscale/setup' # or require 'bootscale/rails'

Under the hood

Bootscale caches the absolute location of all requirable files on the $LOAD_PATH and patches require + autoload to use these absolute paths, thereby avoiding having to check all load paths for every require.

Problem outlined in this talk


If you're experiencing problems with loading your application, especially after moving files around, try deleting the tmp/bootscale folder.


Bug reports and pull requests are welcome on GitHub at

Local development: your load time will be very slow when using a local copy for development like gem 'bootscale', path: '~/Code/bootscal', use via git instead.

Thanks to Aaron Patterson for the idea of converting relative paths to absolute paths.

bootscale open issues Ask a question     (View All Issues)
  • over 3 years Any experience on using it with passenger?
  • over 3 years multiple included blocks error
  • almost 4 years Integrate RMI 2.3 ISeq serialization
  • about 4 years Bootscale/activesupport?
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