Refactor pipeline metrics to reuse `Metrics` class

This commit refactors pipeline metrics to reuse an existing `Metrics`
class. Also it adds a few unit tests for pipeline processing service.

app/services/ci/process_pipeline_service.rb

@@ -9,6 +9,8 @@ module Ci
     end
 
     def execute(trigger_build_ids = nil, initial_process: false)
+      increment_processing_counter
+
       update_retried
 
       if ::Gitlab::Ci::Features.atomic_processing?(pipeline.project)
@@ -22,6 +24,10 @@ module Ci
       end
     end
 
+    def metrics
+      @metrics ||= ::Gitlab::Ci::Pipeline::Metrics.new
+    end
+
     private
 
     # This method is for compatibility and data consistency and should be removed with 9.3 version of GitLab
@@ -43,5 +49,9 @@ module Ci
         .update_all(retried: true) if latest_statuses.any?
     end
     # rubocop: enable CodeReuse/ActiveRecord
+
+    def increment_processing_counter
+      metrics.pipeline_processing_events_counter.increment
+    end
   end
 end

lib/gitlab/ci/pipeline/chain/command.rb

@@ -78,7 +78,7 @@ module Gitlab
           end
 
           def metrics
-            @metrics ||= Chain::Metrics.new
+            @metrics ||= ::Gitlab::Ci::Pipeline::Metrics.new
           end
 
           def observe_creation_duration(duration)

lib/gitlab/ci/pipeline/chain/metrics.rb

-# frozen_string_literal: true
-
-module Gitlab
-  module Ci
-    module Pipeline
-      module Chain
-        class Metrics
-          include Gitlab::Utils::StrongMemoize
-
-          def pipeline_creation_duration_histogram
-            strong_memoize(:pipeline_creation_duration_histogram) do
-              name = :gitlab_ci_pipeline_creation_duration_seconds
-              comment = 'Pipeline creation duration'
-              labels = {}
-              buckets = [0.01, 0.05, 0.1, 0.5, 1.0, 2.0, 5.0, 20.0, 50.0, 240.0]
-
-              ::Gitlab::Metrics.histogram(name, comment, labels, buckets)
-            end
-          end
-
-          def pipeline_size_histogram
-            strong_memoize(:pipeline_size_histogram) do
-              name = :gitlab_ci_pipeline_size_builds
-              comment = 'Pipeline size'
-              labels = { source: nil }
-              buckets = [0, 1, 5, 10, 20, 50, 100, 200, 500, 1000]
-
-              ::Gitlab::Metrics.histogram(name, comment, labels, buckets)
-            end
-          end
-        end
-      end
-    end
-  end
-end

lib/gitlab/ci/pipeline/metrics.rb

+# frozen_string_literal: true
+
+module Gitlab
+  module Ci
+    module Pipeline
+      class Metrics
+        include Gitlab::Utils::StrongMemoize
+
+        def pipeline_creation_duration_histogram
+          strong_memoize(:pipeline_creation_duration_histogram) do
+            name = :gitlab_ci_pipeline_creation_duration_seconds
+            comment = 'Pipeline creation duration'
+            labels = {}
+            buckets = [0.01, 0.05, 0.1, 0.5, 1.0, 2.0, 5.0, 20.0, 50.0, 240.0]
+
+            ::Gitlab::Metrics.histogram(name, comment, labels, buckets)
+          end
+        end
+
+        def pipeline_size_histogram
+          strong_memoize(:pipeline_size_histogram) do
+            name = :gitlab_ci_pipeline_size_builds
+            comment = 'Pipeline size'
+            labels = { source: nil }
+            buckets = [0, 1, 5, 10, 20, 50, 100, 200, 500, 1000]
+
+            ::Gitlab::Metrics.histogram(name, comment, labels, buckets)
+          end
+        end
+
+        def pipeline_processing_events_counter
+          strong_memoize(:pipeline_processing_events_counter) do
+            name = :gitlab_ci_pipeline_processing_events_total
+            comment = 'Total amount of pipeline processing events'
+
+            Gitlab::Metrics.counter(name, comment)
+          end
+        end
+      end
+    end
+  end
+end

spec/services/ci/create_pipeline_service_spec.rb

@@ -80,7 +80,7 @@ RSpec.describe Ci::CreatePipelineService do
       it 'records pipeline size in a prometheus histogram' do
         histogram = spy('pipeline size histogram')
 
-        allow(Gitlab::Ci::Pipeline::Chain::Metrics)
+        allow(Gitlab::Ci::Pipeline::Metrics)
           .to receive(:new).and_return(histogram)
 
         execute_service

spec/services/ci/process_pipeline_service_spec.rb

@@ -10,32 +10,45 @@ RSpec.describe Ci::ProcessPipelineService do
     create(:ci_empty_pipeline, ref: 'master', project: project)
   end
 
+  subject { described_class.new(pipeline) }
+
   before do
     stub_ci_pipeline_to_return_yaml_file
-
     stub_not_protect_default_branch
 
     project.add_developer(user)
   end
 
-  context 'updates a list of retried builds' do
-    subject { described_class.retried.order(:id) }
+  describe 'processing events counter' do
+    let(:metrics) { double('pipeline metrics') }
+    let(:counter) { double('events counter') }
 
+    before do
+      allow(subject)
+        .to receive(:metrics).and_return(metrics)
+      allow(metrics)
+        .to receive(:pipeline_processing_events_counter)
+        .and_return(counter)
+    end
+
+    it 'increments processing events counter' do
+      expect(counter).to receive(:increment)
+
+      subject.execute
+    end
+  end
+
+  describe 'updating a list of retried builds' do
     let!(:build_retried) { create_build('build') }
     let!(:build) { create_build('build') }
     let!(:test) { create_build('test') }
 
     it 'returns unique statuses' do
-      process_pipeline
+      subject.execute
 
       expect(all_builds.latest).to contain_exactly(build, test)
       expect(all_builds.retried).to contain_exactly(build_retried)
     end
-  end
-
-  def process_pipeline
-    described_class.new(pipeline).execute
-  end
 
     def create_build(name, **opts)
       create(:ci_build, :created, pipeline: pipeline, name: name, **opts)
@@ -44,4 +57,5 @@ RSpec.describe Ci::ProcessPipelineService do
     def all_builds
       pipeline.builds.order(:stage_idx, :id)
     end
+  end
 end