Merge branch 'feature/gb/add-pipeline-age-metrics' into 'master'

Add pipeline age Prometheus histogram metric

See merge request !90027

app/models/ci/pipeline.rb

@@ -131,6 +131,7 @@ class Pipeline < Ci::ApplicationRecord
     validates :source, exclusion: { in: %w(unknown), unless: :importing? }, on: :create
 
     after_create :keep_around_commits, unless: :importing?
+    after_find :observe_age_in_minutes, unless: :importing?
 
     use_fast_destroy :job_artifacts
     use_fast_destroy :build_trace_chunks
@@ -1322,6 +1323,16 @@ def has_expired_test_reports?
       end
     end
 
+    def age_in_minutes
+      return 0 unless persisted?
+
+      unless has_attribute?(:created_at)
+        raise ArgumentError, 'pipeline not fully loaded'
+      end
+
+      (Time.current - created_at).ceil / 60
+    end
+
     private
 
     def add_message(severity, content)
@@ -1372,6 +1383,21 @@ def keep_around_commits
       project.repository.keep_around(self.sha, self.before_sha)
     end
 
+    def observe_age_in_minutes
+      return unless age_metric_enabled?
+      return unless persisted? && has_attribute?(:created_at)
+
+      ::Gitlab::Ci::Pipeline::Metrics
+        .pipeline_age_histogram
+        .observe({}, age_in_minutes)
+    end
+
+    def age_metric_enabled?
+      ::Gitlab::SafeRequestStore.fetch(:age_metric_enabled) do
+        ::Feature.enabled?(:ci_pipeline_age_histogram, type: :ops)
+      end
+    end
+
     # Without using `unscoped`, caller scope is also included into the query.
     # Using `unscoped` here will be redundant after Rails 6.1
     def object_hierarchy(options = {})

config/feature_flags/ops/ci_pipeline_age_histogram.yml

+---
+name: ci_pipeline_age_histogram
+introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/90027
+rollout_issue_url: 
+milestone: '15.1'
+type: ops
+group: group::pipeline execution
+default_enabled: false

lib/gitlab/ci/pipeline/metrics.rb

@@ -42,6 +42,15 @@ def self.pipeline_size_histogram
           ::Gitlab::Metrics.histogram(name, comment, labels, buckets)
         end
 
+        def self.pipeline_age_histogram
+          name = :gitlab_ci_pipeline_age_minutes
+          comment = 'Pipeline age histogram'
+          buckets = [5, 30, 120, 720, 1440, 7200, 21600, 43200, 86400, 172800, 518400, 1036800]
+          #          5m 30m 2h   12h  24h   5d    15d    30d    60d    180d    360d    2y
+
+          ::Gitlab::Metrics.histogram(name, comment, {}, buckets)
+        end
+
         def self.active_jobs_histogram
           name = :gitlab_ci_active_jobs
           comment = 'Total amount of active jobs'

spec/models/ci/pipeline_spec.rb

@@ -118,6 +118,38 @@
     end
   end
 
+  describe 'pipeline age metric' do
+    let_it_be(:pipeline) { create(:ci_empty_pipeline, :created) }
+
+    let(:pipeline_age_histogram) do
+      ::Gitlab::Ci::Pipeline::Metrics.pipeline_age_histogram
+    end
+
+    context 'when pipeline age histogram is enabled' do
+      before do
+        stub_feature_flags(ci_pipeline_age_histogram: true)
+      end
+
+      it 'observes pipeline age' do
+        expect(pipeline_age_histogram).to receive(:observe)
+
+        described_class.find(pipeline.id)
+      end
+    end
+
+    context 'when pipeline age histogram is disabled' do
+      before do
+        stub_feature_flags(ci_pipeline_age_histogram: false)
+      end
+
+      it 'observes pipeline age' do
+        expect(pipeline_age_histogram).not_to receive(:observe)
+
+        described_class.find(pipeline.id)
+      end
+    end
+  end
+
   describe '#set_status' do
     let(:pipeline) { build(:ci_empty_pipeline, :created) }
 
@@ -4979,4 +5011,34 @@ def create_bridge(upstream, downstream, depend = false)
       end
     end
   end
+
+  describe '#age_in_minutes' do
+    let(:pipeline) { build(:ci_pipeline) }
+
+    context 'when pipeline has not been persisted' do
+      it 'returns zero' do
+        expect(pipeline.age_in_minutes).to eq 0
+      end
+    end
+
+    context 'when pipeline has been saved' do
+      it 'returns pipeline age in minutes' do
+        pipeline.save!
+
+        travel_to(pipeline.created_at + 2.hours) do
+          expect(pipeline.age_in_minutes).to eq 120
+        end
+      end
+    end
+
+    context 'when pipeline has been loaded without all attributes' do
+      it 'raises an exception' do
+        pipeline.save!
+
+        pipeline_id = Ci::Pipeline.where(id: pipeline.id).select(:id).first
+
+        expect { pipeline_id.age_in_minutes }.to raise_error(ArgumentError)
+      end
+    end
+  end
 end