Merge branch '339665-remove-method_instrumentation_disable_initialization-ff' into 'master'

Disable method instrumentation initialization [RUN ALL RSPEC] [RUN AS-IF-FOSS]

See merge request gitlab-org/gitlab!69662

config/feature_flags/development/method_instrumentation_disable_initialization.yml

----
-name: method_instrumentation_disable_initialization
-introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/69091
-rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/339665
-milestone: '14.3'
-type: development
-group: group::memory
-default_enabled: false

config/initializers/zz_metrics.rb

@@ -162,49 +162,6 @@ if Gitlab::Metrics.enabled? && !Rails.env.test? && !(Rails.env.development? && d
     config.middleware.use(Gitlab::Metrics::ElasticsearchRackMiddleware)
   end
 
-  # We are removing the Instrumentation module entirely in steps.
-  # More in https://gitlab.com/gitlab-org/gitlab/-/issues/217978.
-  unless ::Feature.enabled?(:method_instrumentation_disable_initialization)
-    # This instruments all methods residing in app/models that (appear to) use any
-    # of the ActiveRecord methods. This has to take place _after_ initializing as
-    # for some unknown reason calling eager_load! earlier breaks Devise.
-    Gitlab::Application.config.after_initialize do
-      # We should move all the logic of this file to somewhere else
-      # and require it after `Rails.application.initialize!` in `environment.rb` file.
-      models_path = Rails.root.join('app', 'models').to_s
-
-      Dir.glob("**/*.rb", base: models_path).sort.each do |file|
-        require_dependency file
-      end
-
-      regex = Regexp.union(
-        ActiveRecord::Querying.public_instance_methods(false).map(&:to_s)
-      )
-
-      Gitlab::Metrics::Instrumentation
-        .instrument_class_hierarchy(ActiveRecord::Base) do |klass, method|
-          # Instrumenting the ApplicationSetting class can lead to an infinite
-          # loop. Since the data is cached any way we don't really need to
-          # instrument it.
-          if klass == ApplicationSetting
-            false
-          else
-            loc = method.source_location
-
-            loc && loc[0].start_with?(models_path) && method.source =~ regex
-          end
-        end
-
-      # Ability is in app/models, is not an ActiveRecord model, but should still
-      # be instrumented.
-      Gitlab::Metrics::Instrumentation.instrument_methods(Ability)
-    end
-
-    Gitlab::Metrics::Instrumentation.configure do |config|
-      instrument_classes(config)
-    end
-  end
-
   GC::Profiler.enable
 
   module TrackNewRedisConnections