# Stop monkey patch \`Kernel#require\` **URL:** \ **Category:** APM\ **Tags:** ruby\ **Created:** [May 11, 2020, 12:47pm UTC](https://discuss.elastic.co/t/stop-monkey-patch-kernel-require/232012 "2020-05-11T12:47:44Z")\ **Posts on this page:** 2\ **Page:** 1
**Author:** ![v-kolesnikov](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/v-kolesnikov/32/92395_2.png) [@v-kolesnikov](https://discuss.elastic.co/u/v-kolesnikov)\ **Post date:** [May 11, 2020, 12:47pm UTC](https://discuss.elastic.co/t/stop-monkey-patch-kernel-require/232012/1 "2020-05-11T12:47:44Z")
**APM Agent language and version** : Ruby gem `elastic-apm` 3.6.0 **Steps to reproduce** : ```ruby # frozen_string_literal: true require 'bundler/inline' gemfile do source 'https://rubygems.org' gem 'rack', '~> 2.0', require: false gem 'elastic-apm', '3.6.0', require: false gem 'sidekiq', '6.0.7', require: false gem 'rollbar', '2.25.0', require: false end require 'rack' require 'rack/lobster' require 'elastic_apm' ElasticAPM.start( service_name: 'Lobster', logger: Logger.new(STDOUT), framework_name: 'Rack', framework_version: Rack::VERSION.join('.') ) require 'rollbar' require 'rollbar/middleware/rack' Rollbar.configure {} app = Rack::Builder.new do use ElasticAPM::Middleware use Rollbar::Middleware::Rack run Rack::Lobster.new end at_exit do ElasticAPM.stop end Rack::Server.start(app: app) ``` This simple script (running as `ruby server.rb`) raises an error: ```auto Failed hooking into 'sidekiq'. Please report this at github.com/elastic/apm-agent-ruby ~/.rvm/gems/ruby-2.7.1/gems/elastic-apm-3.6.0/lib/elastic_apm/spies/sidekiq.rb:52:in `install_processor' ~/.rvm/gems/ruby-2.7.1/gems/elastic-apm-3.6.0/lib/elastic_apm/spies/sidekiq.rb:78:in `install' ~/.rvm/rubies/ruby-2.7.1/lib/ruby/2.7.0/forwardable.rb:235:in `install' ~/.rvm/gems/ruby-2.7.1/gems/elastic-apm-3.6.0/lib/elastic_apm/spies.rb:53:in `hook_into' ~/.rvm/gems/ruby-2.7.1/gems/elastic-apm-3.6.0/lib/elastic_apm/spies.rb:78:in `require' ~/.rvm/gems/ruby-2.7.1/gems/sidekiq-6.0.7/lib/sidekiq/scheduled.rb:3:in `' ~/.rvm/gems/ruby-2.7.1/gems/elastic-apm-3.6.0/lib/elastic_apm/spies.rb:75:in `require' ~/.rvm/gems/ruby-2.7.1/gems/elastic-apm-3.6.0/lib/elastic_apm/spies.rb:75:in `require' ~/.rvm/gems/ruby-2.7.1/gems/sidekiq-6.0.7/lib/sidekiq/job_retry.rb:3:in `' ~/.rvm/gems/ruby-2.7.1/gems/elastic-apm-3.6.0/lib/elastic_apm/spies.rb:75:in `require' ~/.rvm/gems/ruby-2.7.1/gems/elastic-apm-3.6.0/lib/elastic_apm/spies.rb:75:in `require' ~/.rvm/gems/ruby-2.7.1/gems/sidekiq-6.0.7/lib/sidekiq/processor.rb:6:in `' ~/.rvm/gems/ruby-2.7.1/gems/elastic-apm-3.6.0/lib/elastic_apm/spies.rb:75:in `require' ~/.rvm/gems/ruby-2.7.1/gems/elastic-apm-3.6.0/lib/elastic_apm/spies.rb:75:in `require' ~/.rvm/gems/ruby-2.7.1/gems/elastic-apm-3.6.0/lib/elastic_apm/spies/sidekiq.rb:50:in `install_processor' ~/.rvm/gems/ruby-2.7.1/gems/elastic-apm-3.6.0/lib/elastic_apm/spies/sidekiq.rb:78:in `install' ~/.rvm/rubies/ruby-2.7.1/lib/ruby/2.7.0/forwardable.rb:235:in `install' ~/.rvm/gems/ruby-2.7.1/gems/elastic-apm-3.6.0/lib/elastic_apm/spies.rb:53:in `hook_into' ~/.rvm/gems/ruby-2.7.1/gems/elastic-apm-3.6.0/lib/elastic_apm/spies.rb:78:in `require' ~/.rvm/gems/ruby-2.7.1/gems/rollbar-2.25.0/lib/rollbar/plugin.rb:98:in `block in require_dependency' ~/.rvm/gems/ruby-2.7.1/gems/rollbar-2.25.0/lib/rollbar/plugin.rb:115:in `all?' ~/.rvm/gems/ruby-2.7.1/gems/rollbar-2.25.0/lib/rollbar/plugin.rb:115:in `dependencies_satisfy?' ~/.rvm/gems/ruby-2.7.1/gems/rollbar-2.25.0/lib/rollbar/plugin.rb:107:in `load?' ~/.rvm/gems/ruby-2.7.1/gems/rollbar-2.25.0/lib/rollbar/plugin.rb:54:in `load!' ~/.rvm/gems/ruby-2.7.1/gems/rollbar-2.25.0/lib/rollbar/plugins.rb:33:in `block in load!' ~/.rvm/gems/ruby-2.7.1/gems/rollbar-2.25.0/lib/rollbar/plugins.rb:32:in `each' ~/.rvm/gems/ruby-2.7.1/gems/rollbar-2.25.0/lib/rollbar/plugins.rb:32:in `load!' ~/.rvm/gems/ruby-2.7.1/gems/rollbar-2.25.0/lib/rollbar.rb:68:in `configure' server.rb:26:in `
' ``` This happens by coincidence, each of which, incidentally, refers to a violation of good manners when writing general-purpose libraries. 1. Patching `Kernel#require` in `ElasticAPM::Spies`: > 1. Unconditional and uncontrolled load 3-rd party dependencies by Rollbar gem. 2. Sidekiq. It is probably the worst code over all Ruby gems ever. The particular issue in that case is requiring `sidekiq` inside one of `Sidekiq`'s module: > The last two are not issues that we could resolve here, but I just listed these to complete the picture. So, what happened in this script? Let's examine: 1. `require 'elastic_apm'` patches `Kernel#require` 2. `Rollbar.configure` requires 'sidekiq' that calls `ElasticAPM::Spies.hook_into('sidekiq')` in patched `Kernel#require`. 3. `ElasticAPM::Spies::SidekiqSpy#install_processor` calls `require 'sidekiq/processor'` that calls `require 'sidekiq'` in `lib/sidekiq/exception_handler.rb` It gives rise a circular dependency that could be illustrated like that: ```ruby # sidekiq.rb module Sidekiq end # sidekiq/processor.rb require 'sidekiq' module Sidekiq module Processor end end # server.rb require 'rollbar' require 'sidekiq' # in patched Kernel#require require 'sidekiq' => true # in Kernel#require_without_apm require 'sidekiq/processor' # in ElasticAPM::Splies::SidekiqSpy#install_processor require 'sidekiq' => false # in Kernel#require_without_apm require 'sidekiq/processor' => false # in Kernel#require_without_apm calls Sidekiq::Processor # raises uninitialized constant Sidekiq::Processor # ... defines Sidekiq::Processor ``` `Sidekiq::Processor` called before than it is defined. So, I understand that it is a complex issue related to all the three gems at the same time. I'll report to other gems as well. But please, consider to give a developers who use your library a chance to manage their application code: don't redefine Kernel module. Please. ---
**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\ **Post date:** [June 1, 2020, 8:47am UTC](https://discuss.elastic.co/t/stop-monkey-patch-kernel-require/232012/2 "2020-06-01T08:47:45Z")
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