Add queue to background transaction metrics

changelogs/unreleased/qmnguyen0711-add-queue-to-background-transaction.yml

+---
+title: Add queue label to metrics dispatched by background transaction
+merge_request: 59344
+author:
+type: changed

lib/gitlab/metrics/background_transaction.rb

@@ -34,8 +34,9 @@ module Gitlab
 
       def labels
         @labels ||= {
-          endpoint_id: current_context&.get_attribute(:caller_id),
-          feature_category: current_context&.get_attribute(:feature_category)
+          endpoint_id: endpoint_id,
+          feature_category: feature_category,
+          queue: queue
         }
       end
 
@@ -44,6 +45,21 @@ module Gitlab
       def current_context
         Labkit::Context.current
       end
+
+      def feature_category
+        current_context&.get_attribute(:feature_category)
+      end
+
+      def endpoint_id
+        current_context&.get_attribute(:caller_id)
+      end
+
+      def queue
+        worker_class = endpoint_id.to_s.safe_constantize
+        return if worker_class.blank? || !worker_class.respond_to?(:queue)
+
+        worker_class.queue.to_s
+      end
     end
   end
 end

spec/lib/gitlab/metrics/background_transaction_spec.rb

@@ -29,17 +29,60 @@ RSpec.describe Gitlab::Metrics::BackgroundTransaction do
   end
 
   describe '#labels' do
+    context 'when the worker queue is accessible' do
+      before do
+        test_worker_class = Class.new do
+          def self.queue
+            'test_worker'
+          end
+        end
+        stub_const('TestWorker', test_worker_class)
+      end
+
+      it 'provides labels with endpoint_id, feature_category and queue' do
+        Gitlab::ApplicationContext.with_raw_context(feature_category: 'projects', caller_id: 'TestWorker') do
+          expect(transaction.labels).to eq({ endpoint_id: 'TestWorker', feature_category: 'projects', queue: 'test_worker' })
+        end
+      end
+    end
+
+    context 'when the worker name does not exist' do
+      it 'provides labels with endpoint_id and feature_category' do
+        # 123TestWorker is an invalid constant
+        Gitlab::ApplicationContext.with_raw_context(feature_category: 'projects', caller_id: '123TestWorker') do
+          expect(transaction.labels).to eq({ endpoint_id: '123TestWorker', feature_category: 'projects', queue: nil })
+        end
+      end
+    end
+
+    context 'when the worker queue is not accessible' do
+      before do
+        stub_const('TestWorker', Class.new)
+      end
+
       it 'provides labels with endpoint_id and feature_category' do
         Gitlab::ApplicationContext.with_raw_context(feature_category: 'projects', caller_id: 'TestWorker') do
-        expect(transaction.labels).to eq({ endpoint_id: 'TestWorker', feature_category: 'projects' })
+          expect(transaction.labels).to eq({ endpoint_id: 'TestWorker', feature_category: 'projects', queue: nil })
+        end
       end
     end
   end
 
   RSpec.shared_examples 'metric with labels' do |metric_method|
+    before do
+      test_worker_class = Class.new do
+        def self.queue
+          'test_worker'
+        end
+      end
+      stub_const('TestWorker', test_worker_class)
+    end
+
     it 'measures with correct labels and value' do
       value = 1
-      expect(prometheus_metric).to receive(metric_method).with({ endpoint_id: 'TestWorker', feature_category: 'projects' }, value)
+      expect(prometheus_metric).to receive(metric_method).with({
+        endpoint_id: 'TestWorker', feature_category: 'projects', queue: 'test_worker'
+      }, value)
 
       Gitlab::ApplicationContext.with_raw_context(feature_category: 'projects', caller_id: 'TestWorker') do
         transaction.send(metric_method, :test_metric, value)