Benchmark Ruby's `require` for Debugging Glory
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Have a Ruby project that has stopped loading, and you aren't sure where the issue is?

Knowing the last file that was successfully "required" by Ruby can be helpful in diagnosing the issue. This gem will help you find that last required file. It can also help you see where expensive (slow) processing is occurring, by adding Benchmark.realtime to every require, and printing the result for every file.

This is an extraction of a debugging tool that I have copy/pasted into many projects over the years, and it is now time to set it free.

Warning: This gem is for debugging problems. It uses a global $ variable, which is sad practice. It uses it as a safety semaphore, so I consider it justified. If you can think of a better way to implement the safety semaphore, let me know!

Caveat: This gem has no effects unless a particular environment variable is set. It does nothing at all unless it is 'invoked' by detection of the environment variable (ENV['REQUIRE_BENCH'] == 'true'). The Warning above is mitigated by the gem not having any of its code activated under normal circumstances.

Project RequireBench
gem name require_bench
license License: MIT
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Add this line to your application's Gemfile:

gem 'require_bench'

And then execute:

$ bundle

Or install it yourself as:

$ gem install require_bench


Require the library where it will be loaded prior to any other requires you want to benchmark.

require 'require_bench'

By default this gem does nothing, hacks nothing, and has zero effects.

Turn on benchmarking & output

Add an environment variable, however you normally do such things, so that in Ruby:

ENV['REQUIRE_BENCH'] == 'true'

Any value other than 'true' means RequireBench is still turned off.

Handy Rake Task for Rails:

Require in Rakefile, as follows:

  require 'bundler/setup'
  require 'require_bench/tasks' # Near the top, just below require 'bundler/setup'!

This will ensure it will load before other stuff.

When running from command line, you will see output as the Rails app boots.

∴ REQUIRE_BENCH=true bundle exec rake require_bench:hello
[RequireBench]  12.179703 /path/to/my_app/config/application
[RequireBench]   0.001726 resque/tasks
[RequireBench]   0.000917 resque/scheduler/tasks
[RequireBench]   0.000011 rake
[RequireBench]   0.000014 active_record
[RequireBench]   0.008673 sprockets/rails/task
[RequireBench]   0.000012 dynamoid
[RequireBench]   0.000004 dynamoid/tasks/database
[RequireBench]   0.000012 raven/integrations/tasks
[RequireBench]   0.003107 rspec/core/rake_task
[RequireBench]   0.000017 csv
[RequireBench]   0.000012 resque/tasks
[RequireBench]   0.000007 resque/scheduler/tasks
[RequireBench]   0.064950 rails/tasks
[RequireBench]   0.003305 rake/testtask
[RequireBench]   0.001886 rubocop/rake_task
[RequireBench]   0.000012 hubspot-ruby
[RequireBench]   2.291259 /path/to/my_app/config/environment.rb

[RequireBench] Slowest Loads by Library, in order
 1.  11.914224 /path/to/my_app/config/application
 2.   2.153282 /path/to/my_app/config/environment.rb
 3.   0.061008 rails
 4.   0.010827 sprockets
 5.   0.003179 rspec
 6.   0.003144 rake
 7.   0.003127 resque
 8.   0.001543 rubocop
 9.   0.000021 dynamoid
10.   0.000016 csv
11.   0.000016 active_record
12.   0.000010 raven
13.   0.000005 hubspot-ruby
 14.150402 TOTAL

Output Options

If the output is too noisy from deep libraries you can add a regex to skip benchmarking of files that match.

If the value is set in the shell, it should be a string. RequireBench will split the string by comma, Regexp escape each value, and join together with pipe (|) to form the regex pattern.

export REQUIRE_BENCH_SKIP_PATTERN=activesupport,rspec

If the ENV['REQUIRE_BENCH_SKIP_PATTERN'] value is set in Ruby, it can be one of:

  • a string, to be split by comma, each Regexp escaped, then joined by pipe (|)
  • an array of strings, each to be Regexp escaped, then joined by pipe (|)
  • a Regexp object, which will be used as is.
ENV['REQUIRE_BENCH_SKIP_PATTERN'] = 'activesupport,rspec'
# or
ENV['REQUIRE_BENCH_SKIP_PATTERN'] = [ 'activesupport', 'rspec' ]
# or
ENV['REQUIRE_BENCH_SKIP_PATTERN'] ='activesupport|rspec')

Any file being required that matches the pattern will use the standard, rather than the benchmarked, require.

Fully qualified paths

Fully qualified paths, or any portion thereof, are fine, because the strings are always Regexp escaped.


After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to


Bug reports and pull requests are welcome on GitHub at

Code of Conduct

Everyone interacting in the AnonymousActiveRecord project’s codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.


This library aims to adhere to Semantic Versioning 2.0.0. Violations of this scheme should be reported as bugs. Specifically, if a minor or patch version is released that breaks backward compatibility, a new version should be immediately released that restores compatibility. Breaking changes to the public API will only be introduced with new major versions.

As a result of this policy, you can (and should) specify a dependency on this gem using the Pessimistic Version Constraint with two digits of precision.

For example:

spec.add_dependency 'require_bench', '~> 0.0'


License: MIT