Instrument methods used in email diffs

CHANGELOG

@@ -19,6 +19,9 @@ v 8.8.0 (unreleased)
   - Added multiple colors for labels in dropdowns when dups happen.
   - Improve description for the Two-factor Authentication sign-in screen. (Connor Shea)
 
+v 8.7.3
+  - Emails, Gitlab::Email::Message, Gitlab::Diff, and Premailer::Adapter::Nokogiri are now instrumented
+
 v 8.7.2
   - The "New Branch" button is now loaded asynchronously
   - Fix error 500 when trying to create a wiki page

config/initializers/metrics.rb

@@ -61,12 +61,30 @@ if Gitlab::Metrics.enabled?
       config.instrument_instance_methods(const)
     end
 
-    Dir[Rails.root.join('app', 'finders', '*.rb')].each do |path|
-      const = File.basename(path, '.rb').camelize.constantize
-
-      config.instrument_instance_methods(const)
+    # Path to search => prefix to strip from constant
+    paths_to_instrument = {
+      ['app', 'finders']                    => ['app', 'finders'],
+      ['app', 'mailers', 'emails']          => ['app', 'mailers'],
+      ['app', 'services', '**']             => ['app', 'services'],
+      ['lib', 'gitlab', 'diff']             => ['lib'],
+      ['lib', 'gitlab', 'email', 'message'] => ['lib']
+    }
+
+    paths_to_instrument.each do |(path, prefix)|
+      prefix = Rails.root.join(*prefix)
+
+      Dir[Rails.root.join(*path + ['*.rb'])].each do |file_path|
+        path = Pathname.new(file_path).relative_path_from(prefix)
+        const = path.to_s.sub('.rb', '').camelize.constantize
+
+        config.instrument_methods(const)
+        config.instrument_instance_methods(const)
+      end
     end
 
+    config.instrument_methods(Premailer::Adapter::Nokogiri)
+    config.instrument_instance_methods(Premailer::Adapter::Nokogiri)
+
     [
       :Blame, :Branch, :BranchCollection, :Blob, :Commit, :Diff, :Repository,
       :Tag, :TagCollection, :Tree
@@ -97,17 +115,6 @@ if Gitlab::Metrics.enabled?
     config.instrument_methods(Gitlab::ReferenceExtractor)
     config.instrument_instance_methods(Gitlab::ReferenceExtractor)
 
-    # Instrument all service classes
-    services = Rails.root.join('app', 'services')
-
-    Dir[services.join('**', '*.rb')].each do |file_path|
-      path = Pathname.new(file_path).relative_path_from(services)
-      const = path.to_s.sub('.rb', '').camelize.constantize
-
-      config.instrument_methods(const)
-      config.instrument_instance_methods(const)
-    end
-
     # Instrument the classes used for checking if somebody has push access.
     config.instrument_instance_methods(Gitlab::GitAccess)
     config.instrument_instance_methods(Gitlab::GitAccessWiki)