Refactor dashboard proccesing into stages

app/controllers/projects/environments_controller.rb

@@ -162,7 +162,7 @@ class Projects::EnvironmentsController < Projects::ApplicationController
 
     respond_to do |format|
       format.json do
-        dashboard = MetricsDashboardService.new(@project).get_dashboard
+        dashboard = Gitlab::MetricsDashboard::Service.new(@project).get_dashboard
 
         render json: dashboard, status: :ok
       end

app/services/metrics_dashboard_service.rb

-# frozen_string_literal: true
-
-# Fetches the metrics dashboard layout and supplemented the output with DB info.
-class MetricsDashboardService
-  SYSTEM_DASHBOARD_NAME = 'common_metrics'
-  SYSTEM_DASHBOARD_PATH = Rails.root.join('config', 'prometheus', "#{SYSTEM_DASHBOARD_NAME}.yml")
-
-  def initialize(project)
-    @project = project
-  end
-
-  # Returns a DB-supplemented json representation of a dashboard config file.
-  def get_dashboard
-    dashboard = Rails.cache.fetch(cache_key) { system_dashboard }
-
-    process_dashboard(dashboard)
-  end
-
-  private
-
-  # Returns the base metrics shipped with every GitLab service.
-  def system_dashboard
-    YAML.load_file(SYSTEM_DASHBOARD_PATH)
-  end
-
-  def cache_key
-    "metrics_dashboard_#{SYSTEM_DASHBOARD_NAME}"
-  end
-
-  def process_dashboard(dashboard)
-    MetricsDashboardProcessingService.new(dashboard, @project).process
-  end
-end

lib/gitlab/metrics_dashboard/common_metrics_inserter.rb

+# frozen_string_literal: true
+
+module Gitlab
+  module MetricsDashboard
+    class CommonMetricsInserter
+      class << self
+        # For each metric in the dashboard config, attempts to find a corresponding
+        # database record. If found, includes the record's id in the dashboard config.
+        def transform!(dashboard, _project)
+          common_metrics = ::PrometheusMetric.common
+
+          for_metrics(dashboard) do |metric|
+            metric_record = common_metrics.find { |m| m.identifier == metric[:id] }
+            metric[:metric_id] = metric_record.id if metric_record
+          end
+        end
+
+        private
+
+        def for_metrics(dashboard)
+          dashboard[:panel_groups].each do |panel_group|
+            panel_group[:panels].each do |panel|
+              panel[:metrics].each do |metric|
+                yield metric
+              end
+            end
+          end
+        end
+      end
+    end
+  end
+end

lib/gitlab/metrics_dashboard/processor.rb

+# frozen_string_literal: true
+
+module Gitlab
+  module MetricsDashboard
+    class Processor
+      STAGES = [CommonMetricsInserter, Sorter, ProjectMetricsInserter]
+
+      def initialize(dashboard, project)
+        @dashboard = dashboard.deep_transform_keys(&:to_sym)
+        @project = project
+      end
+
+      def process
+        STAGES.each { |stage| stage.transform!(@dashboard, @project) }
+
+        @dashboard.to_json
+      end
+    end
+  end
+end

lib/gitlab/metrics_dashboard/project_metrics_inserter.rb

+# frozen_string_literal: true
+
+module Gitlab
+  module MetricsDashboard
+    class ProjectMetricsInserter
+      DEFAULT_PANEL_TYPE = 'area-chart'
+
+      class << self
+        # Inserts project-specific metrics into the dashboard config.
+        # If there are no project-specific metrics, this will have no effect.
+        def transform!(dashboard, project)
+          project.prometheus_metrics.each do |project_metric|
+            group = find_or_create(:panel_group, dashboard[:panel_groups], project_metric)
+            panel = find_or_create(:panel, group[:panels], project_metric)
+            find_or_create(:metric, panel[:metrics], project_metric)
+          end
+        end
+
+        # Looks for an instance of the named resource corresponding to the provided
+        # metric object. If unavailable, inserts one.
+        # @param name [Symbol, String] One of :panel_group, :panel, or :metric
+        # @param existing_resources [Array<Hash>]
+        # @param metric [PrometheusMetric]
+        def find_or_create(name, existing_resources, metric)
+          target = self.send("find_#{name}", existing_resources, metric)
+          return target if target
+
+          target = self.send("new_#{name}", metric)
+          existing_resources << target
+
+          target
+        end
+
+        def find_panel_group(panel_groups, metric)
+          panel_groups.find { |group| group[:group] == metric.group_title }
+        end
+
+        def find_panel(panels, metric)
+          panel_identifiers = [DEFAULT_PANEL_TYPE, metric.title, metric.y_label]
+          target_panel = panels.find { |panel| panel.values_at(:type, :title, :y_label) == panel_identifiers }
+        end
+
+        def find_metric(metrics, metric)
+          metrics.find { |m| m[:id] == metric.identifier }
+        end
+
+        def new_panel_group(metric)
+          {
+            group: metric.group_title,
+            priority: metric.priority,
+            panels: []
+          }
+        end
+
+        def new_panel(metric)
+          {
+            type: DEFAULT_PANEL_TYPE,
+            title: metric.title,
+            y_label: metric.y_label,
+            metrics: []
+          }
+        end
+
+        def new_metric(metric)
+          metric.queries.first.merge(metric_id: metric.id)
+        end
+      end
+    end
+  end
+end

lib/gitlab/metrics_dashboard/service.rb

+# frozen_string_literal: true
+
+# Fetches the metrics dashboard layout and supplemented the output with DB info.
+module Gitlab
+  module MetricsDashboard
+    class Service
+      SYSTEM_DASHBOARD_NAME = 'common_metrics'
+      SYSTEM_DASHBOARD_PATH = Rails.root.join('config', 'prometheus', "#{SYSTEM_DASHBOARD_NAME}.yml")
+
+      def initialize(project)
+        @project = project
+      end
+
+      # Returns a DB-supplemented json representation of a dashboard config file.
+      def get_dashboard
+        dashboard = Rails.cache.fetch(cache_key) { system_dashboard }
+
+        process_dashboard(dashboard)
+      end
+
+      private
+
+      # Returns the base metrics shipped with every GitLab service.
+      def system_dashboard
+        YAML.load_file(SYSTEM_DASHBOARD_PATH)
+      end
+
+      def cache_key
+        "metrics_dashboard_#{SYSTEM_DASHBOARD_NAME}"
+      end
+
+      def process_dashboard(dashboard)
+        Processor.new(dashboard, @project).process
+      end
+    end
+  end
+end

lib/gitlab/metrics_dashboard/sorter.rb

+# frozen_string_literal: true
+
+module Gitlab
+  module MetricsDashboard
+    class Sorter
+      class << self
+        def transform!(dashboard, _project)
+          sort_groups!(dashboard)
+          sort_panels!(dashboard)
+        end
+
+        # Sorts the groups in the dashboard by the :priority key
+        def sort_groups!(dashboard)
+          dashboard[:panel_groups] = dashboard[:panel_groups].sort_by { |group| group[:priority] }
+        end
+
+        # Sorts the panels in the dashboard by the :weight key
+        def sort_panels!(dashboard)
+          dashboard[:panel_groups].each do |group|
+            group[:panels] = group[:panels].sort_by { |panel| panel[:weight] }
+          end
+        end
+      end
+    end
+  end
+end

spec/services/metrics_dashboard_processing_service_spec.rb → spec/lib/gitlab/metrics_dashboard/processor_spec.rb

 require 'spec_helper'
 
-describe MetricsDashboardProcessingService do
+describe Gitlab::MetricsDashboard::Processor do
   let(:project) { build(:project) }
   let(:dashboard_yml) { YAML.load_file('spec/fixtures/services/metrics_dashboard_processing_service.yml') }
 
@@ -40,7 +40,7 @@ describe MetricsDashboardProcessingService do
     end
 
     it 'orders groups by priority and panels by weight' do
-      expected_metrics_order = %w('metric_b metric_a2 metric_a1')
+      expected_metrics_order = %w(metric_b metric_a2 metric_a1)
       actual_metrics_order = all_metrics.map { |m| m[:id] }
 
       expect(actual_metrics_order).to eq expected_metrics_order

spec/services/metrics_dashboard_service_spec.rb → spec/lib/gitlab/metrics_dashboard/service_spec.rb

 require 'spec_helper'
 
-describe MetricsDashboardService, :use_clean_rails_memory_store_caching do
+describe Gitlab::MetricsDashboard::Service, :use_clean_rails_memory_store_caching do
   let(:project) { build(:project) }
 
   describe 'get_dashboard' do