Convert active record

lib/gitlab/metrics/subscribers/active_record.rb

@@ -3,12 +3,13 @@ module Gitlab
     module Subscribers
       # Class for tracking the total query duration of a transaction.
       class ActiveRecord < ActiveSupport::Subscriber
+        include Gitlab::Metrics::Concern
         attach_to :active_record
 
         def sql(event)
           return unless current_transaction
 
-          metric_sql_duration_seconds.observe(current_transaction.labels, event.duration / 1000.0)
+          self.class.gitlab_sql_duration_seconds.observe(current_transaction.labels, event.duration / 1000.0)
 
           current_transaction.increment(:sql_duration, event.duration, false)
           current_transaction.increment(:sql_count, 1, false)
@@ -16,17 +17,14 @@ module Gitlab
 
         private
 
-        def current_transaction
-          Transaction.current
+        define_histogram :gitlab_sql_duration_seconds do
+          docstring 'SQL time'
+          base_labels Transaction::BASE_LABELS
+          buckets [0.001, 0.01, 0.1, 10.0]
         end
 
-        def metric_sql_duration_seconds
-          @metric_sql_duration_seconds ||= Gitlab::Metrics.histogram(
-            :gitlab_sql_duration_seconds,
-            'SQL time',
-            Transaction::BASE_LABELS,
-            [0.001, 0.01, 0.1, 10.0]
-          )
+        def current_transaction
+          Transaction.current
         end
       end
     end

spec/lib/gitlab/metrics/subscribers/active_record_spec.rb

@@ -25,7 +25,7 @@ describe Gitlab::Metrics::Subscribers::ActiveRecord do
         expect(subscriber).to receive(:current_transaction)
                                 .at_least(:once)
                                 .and_return(transaction)
-        expect(subscriber.send(:metric_sql_duration_seconds)).to receive(:observe).with({}, 0.002)
+        expect(described_class.send(:gitlab_sql_duration_seconds)).to receive(:observe).with({}, 0.002)
         subscriber.sql(event)
       end