Move prometheus metrics to module. Use class instance variables for metrics...

Move prometheus metrics to module. Use class instance variables for metrics and metrics cache in metrics concern

lib/gitlab/metrics.rb

 module Gitlab
   module Metrics
     extend Gitlab::Metrics::InfluxDb
-    extend Gitlab::Metrics::Prometheus
+    include Gitlab::Metrics::Prometheus
 
     def self.enabled?
       influx_metrics_enabled? || prometheus_metrics_enabled?

lib/gitlab/metrics/concern.rb

@@ -6,12 +6,13 @@ module Gitlab
       extend ActiveSupport::Concern
 
       included do
-        @@_metric_provider_mutex = Mutex.new
+        @_metric_provider_mutex = Mutex.new
+        @_metrics_provider_cache = {}
       end
 
       class_methods do
         def reload_metric!(name)
-          @_metrics_provider_cache&.delete(name)
+          @_metrics_provider_cache.delete(name)
         end
 
         private
@@ -22,12 +23,12 @@ module Gitlab
           end
 
           define_singleton_method(name) do
-            @_metrics_provider_cache&.[](name) || init_metric(type, name, opts, &block)
+            @_metrics_provider_cache[name] || init_metric(type, name, opts, &block)
           end
         end
 
         def fetch_metric(type, name, opts = {}, &block)
-          @_metrics_provider_cache&.[](name) || init_metric(type, name, opts, &block)
+          @_metrics_provider_cache[name] || init_metric(type, name, opts, &block)
         end
 
         def init_metric(type, name, opts = {}, &block)
@@ -42,8 +43,7 @@ module Gitlab
         end
 
         def synchronized_cache_fill(key)
-          @@_metric_provider_mutex.synchronize do
-            @_metrics_provider_cache ||= {}
+          @_metric_provider_mutex.synchronize do
             @_metrics_provider_cache[key] ||= yield
           end
         end

lib/gitlab/metrics/influx_db.rb

 module Gitlab
   module Metrics
     module InfluxDb
-      include Gitlab::Metrics::Concern::ClassMethods
+      include Gitlab::Metrics::Concern
       include Gitlab::CurrentSettings
       extend self
 

lib/gitlab/metrics/prometheus.rb

@@ -3,73 +3,78 @@ require 'prometheus/client'
 module Gitlab
   module Metrics
     module Prometheus
+      extend ActiveSupport::Concern
+      include Gitlab::Metrics::Concern
       include Gitlab::CurrentSettings
-      include Gitlab::Utils::StrongMemoize
 
       REGISTRY_MUTEX = Mutex.new
       PROVIDER_MUTEX = Mutex.new
 
-      def metrics_folder_present?
-        multiprocess_files_dir = ::Prometheus::Client.configuration.multiprocess_files_dir
+      class_methods do
+        include Gitlab::Utils::StrongMemoize
 
-        multiprocess_files_dir &&
-          ::Dir.exist?(multiprocess_files_dir) &&
-          ::File.writable?(multiprocess_files_dir)
-      end
+        def metrics_folder_present?
+          multiprocess_files_dir = ::Prometheus::Client.configuration.multiprocess_files_dir
 
-      def prometheus_metrics_enabled?
-        strong_memoize(:prometheus_metrics_enabled) do
-          prometheus_metrics_enabled_unmemoized
+          multiprocess_files_dir &&
+            ::Dir.exist?(multiprocess_files_dir) &&
+            ::File.writable?(multiprocess_files_dir)
+        end
+
+        def prometheus_metrics_enabled?
+          strong_memoize(:prometheus_metrics_enabled) do
+            prometheus_metrics_enabled_unmemoized
+          end
         end
-      end
 
-      def registry
-        strong_memoize(:registry) do
-          REGISTRY_MUTEX.synchronize do
-            strong_memoize(:registry) do
-              ::Prometheus::Client.registry
+        def registry
+          strong_memoize(:registry) do
+            REGISTRY_MUTEX.synchronize do
+              strong_memoize(:registry) do
+                ::Prometheus::Client.registry
+              end
             end
           end
         end
-      end
 
-      def counter(name, docstring, base_labels = {})
-        safe_provide_metric(:counter, name, docstring, base_labels)
-      end
+        def counter(name, docstring, base_labels = {})
+          safe_provide_metric(:counter, name, docstring, base_labels)
+        end
 
-      def summary(name, docstring, base_labels = {})
-        safe_provide_metric(:summary, name, docstring, base_labels)
-      end
+        def summary(name, docstring, base_labels = {})
+          safe_provide_metric(:summary, name, docstring, base_labels)
+        end
 
-      def gauge(name, docstring, base_labels = {}, multiprocess_mode = :all)
-        safe_provide_metric(:gauge, name, docstring, base_labels, multiprocess_mode)
-      end
+        def gauge(name, docstring, base_labels = {}, multiprocess_mode = :all)
+          safe_provide_metric(:gauge, name, docstring, base_labels, multiprocess_mode)
+        end
 
-      def histogram(name, docstring, base_labels = {}, buckets = ::Prometheus::Client::Histogram::DEFAULT_BUCKETS)
-        safe_provide_metric(:histogram, name, docstring, base_labels, buckets)
-      end
+        def histogram(name, docstring, base_labels = {}, buckets = ::Prometheus::Client::Histogram::DEFAULT_BUCKETS)
+          safe_provide_metric(:histogram, name, docstring, base_labels, buckets)
+        end
 
-      private
+        private
 
-      def safe_provide_metric(method, name, *args)
-        metric = provide_metric(name)
-        return metric if metric
+        def safe_provide_metric(method, name, *args)
+          metric = provide_metric(name)
+          return metric if metric
 
-        PROVIDER_MUTEX.synchronize do
-          provide_metric(name) || registry.method(method).call(name, *args)
+          PROVIDER_MUTEX.synchronize do
+            provide_metric(name) || registry.method(method).call(name, *args)
+          end
         end
-      end
 
-      def provide_metric(name)
-        if prometheus_metrics_enabled?
-          registry.get(name)
-        else
-          NullMetric.instance
+        def provide_metric(name)
+          if prometheus_metrics_enabled?
+            registry.get(name)
+          else
+            NullMetric.instance
+          end
         end
-      end
 
-      def prometheus_metrics_enabled_unmemoized
-        metrics_folder_present? && current_application_settings[:prometheus_metrics_enabled] || false
+        def prometheus_metrics_enabled_unmemoized
+          metrics_folder_present? && current_application_settings[:prometheus_metrics_enabled] || false
+        end
       end
     end
   end