Memoize only yaml loading method

lib/gitlab/prometheus/additional_metrics_parser.rb

@@ -23,11 +23,11 @@ module Gitlab
       end
 
       def additional_metrics_raw
-        @additional_metrics_raw ||= load_yaml_file&.map(&:deep_symbolize_keys).freeze
+        load_yaml_file&.map(&:deep_symbolize_keys).freeze
       end
 
       def load_yaml_file
-        YAML.load_file(Rails.root.join('config/prometheus/additional_metrics.yml'))
+        @loaded_yaml_file ||= YAML.load_file(Rails.root.join('config/prometheus/additional_metrics.yml'))
       end
     end
   end

spec/lib/gitlab/prometheus/additional_metrics_parser_spec.rb

@@ -33,7 +33,6 @@ describe Gitlab::Prometheus::AdditionalMetricsParser, lib: true do
       end
 
       before do
-        described_class.instance_variable_set :@additional_metrics_raw, nil
         allow(described_class).to receive(:load_yaml_file) { YAML.load(sample_yaml) }
       end
 
@@ -68,10 +67,6 @@ describe Gitlab::Prometheus::AdditionalMetricsParser, lib: true do
     end
 
     shared_examples 'required field' do |field_name|
-      before do
-        described_class.instance_variable_set :@additional_metrics_raw, nil
-      end
-
       context "when #{field_name} is nil" do
         before do
           allow(described_class).to receive(:load_yaml_file) { YAML.load(field_missing) }