Refactor predefined dashboards

Move code for predefined dashboards into a common class that can be
inherited from.

app/services/metrics/dashboard/base_embed_service.rb

@@ -13,7 +13,7 @@ module Metrics
 
       def dashboard_path
         params[:dashboard_path].presence ||
-          ::Metrics::Dashboard::SystemDashboardService::SYSTEM_DASHBOARD_PATH
+          ::Metrics::Dashboard::SystemDashboardService::DASHBOARD_PATH
       end
 
       def group

app/services/metrics/dashboard/custom_metric_embed_service.rb

@@ -40,7 +40,7 @@ module Metrics
         # All custom metrics are displayed on the system dashboard.
         # Nil is acceptable as we'll default to the system dashboard.
         def valid_dashboard?(dashboard)
-          dashboard.nil? || ::Metrics::Dashboard::SystemDashboardService.system_dashboard?(dashboard)
+          dashboard.nil? || ::Metrics::Dashboard::SystemDashboardService.matching_dashboard?(dashboard)
         end
       end
 

app/services/metrics/dashboard/predefined_dashboard_service.rb

+# frozen_string_literal: true
+
+module Metrics
+  module Dashboard
+    class PredefinedDashboardService < ::Metrics::Dashboard::BaseService
+      # These constants should be overridden in the inheriting class. For Ex:
+      # DASHBOARD_PATH = 'config/prometheus/common_metrics.yml'
+      # DASHBOARD_NAME = 'Default'
+      DASHBOARD_PATH = nil
+      DASHBOARD_NAME = nil
+
+      SEQUENCE = [
+        STAGES::EndpointInserter,
+        STAGES::Sorter
+      ].freeze
+
+      class << self
+        def matching_dashboard?(filepath)
+          filepath == self::DASHBOARD_PATH
+        end
+      end
+
+      private
+
+      def cache_key
+        "metrics_dashboard_#{dashboard_path}"
+      end
+
+      def dashboard_path
+        self.class::DASHBOARD_PATH
+      end
+
+      # Returns the base metrics shipped with every GitLab service.
+      def get_raw_dashboard
+        yml = File.read(Rails.root.join(dashboard_path))
+
+        YAML.safe_load(yml)
+      end
+
+      def sequence
+        self.class::SEQUENCE
+      end
+    end
+  end
+end

app/services/metrics/dashboard/system_dashboard_service.rb

 # frozen_string_literal: true
 
 # Fetches the system metrics dashboard and formats the output.
-# Use Gitlab::Metrics::Dashboard::Finder to retrive dashboards.
+# Use Gitlab::Metrics::Dashboard::Finder to retrieve dashboards.
 module Metrics
   module Dashboard
-    class SystemDashboardService < ::Metrics::Dashboard::BaseService
-      SYSTEM_DASHBOARD_PATH = 'config/prometheus/common_metrics.yml'
-      SYSTEM_DASHBOARD_NAME = 'Default'
+    class SystemDashboardService < ::Metrics::Dashboard::PredefinedDashboardService
+      DASHBOARD_PATH = 'config/prometheus/common_metrics.yml'
+      DASHBOARD_NAME = 'Default'
 
       SEQUENCE = [
         STAGES::CommonMetricsInserter,
@@ -18,37 +18,12 @@ module Metrics
       class << self
         def all_dashboard_paths(_project)
           [{
-            path: SYSTEM_DASHBOARD_PATH,
-            display_name: SYSTEM_DASHBOARD_NAME,
+            path: DASHBOARD_PATH,
+            display_name: DASHBOARD_NAME,
             default: true,
             system_dashboard: true
           }]
         end
-
-        def system_dashboard?(filepath)
-          filepath == SYSTEM_DASHBOARD_PATH
-        end
-      end
-
-      private
-
-      def cache_key
-        "metrics_dashboard_#{dashboard_path}"
-      end
-
-      def dashboard_path
-        SYSTEM_DASHBOARD_PATH
-      end
-
-      # Returns the base metrics shipped with every GitLab service.
-      def get_raw_dashboard
-        yml = File.read(Rails.root.join(dashboard_path))
-
-        YAML.safe_load(yml)
-      end
-
-      def sequence
-        SEQUENCE
       end
     end
   end

ee/app/services/metrics/dashboard/cluster_dashboard_service.rb

@@ -4,36 +4,15 @@
 # Use Gitlab::Metrics::Dashboard::Finder to retrive dashboards.
 module Metrics
   module Dashboard
-    class ClusterDashboardService < ::Metrics::Dashboard::BaseService
-      CLUSTER_DASHBOARD_PATH = 'ee/config/prometheus/cluster_metrics.yml'
-      CLUSTER_DASHBOARD_NAME = 'Cluster'
+    class ClusterDashboardService < ::Metrics::Dashboard::PredefinedDashboardService
+      DASHBOARD_PATH = 'ee/config/prometheus/cluster_metrics.yml'
+      DASHBOARD_NAME = 'Cluster'
 
       SEQUENCE = [
         STAGES::CommonMetricsInserter,
         STAGES::ClusterEndpointInserter,
         STAGES::Sorter
       ].freeze
-
-      private
-
-      def cache_key
-        "metrics_dashboard_#{dashboard_path}"
-      end
-
-      def dashboard_path
-        CLUSTER_DASHBOARD_PATH
-      end
-
-      # Returns the base metrics shipped with every GitLab service.
-      def get_raw_dashboard
-        yml = File.read(Rails.root.join(dashboard_path))
-
-        YAML.safe_load(yml)
-      end
-
-      def sequence
-        SEQUENCE
-      end
     end
   end
 end

ee/spec/services/metrics/dashboard/cluster_dashboard_service_spec.rb

@@ -19,13 +19,7 @@ describe Metrics::Dashboard::ClusterDashboardService, :use_clean_rails_memory_st
     let(:service_call) { described_class.new(*service_params).get_dashboard }
 
     it_behaves_like 'valid dashboard service response'
-
-    it 'caches the unprocessed dashboard for subsequent calls' do
-      expect(YAML).to receive(:safe_load).once.and_call_original
-
-      described_class.new(*service_params).get_dashboard
-      described_class.new(*service_params).get_dashboard
-    end
+    it_behaves_like 'caches the unprocessed dashboard for subsequent calls'
 
     context 'when called with a non-system dashboard' do
       let(:dashboard_path) { 'garbage/dashboard/path' }

lib/gitlab/metrics/dashboard/service_selector.rb

@@ -34,7 +34,7 @@ module Gitlab
           end
 
           def system_dashboard?(filepath)
-            SERVICES::SystemDashboardService.system_dashboard?(filepath)
+            SERVICES::SystemDashboardService.matching_dashboard?(filepath)
           end
 
           def custom_metric_embed?(params)

spec/services/metrics/dashboard/system_dashboard_service_spec.rb

@@ -14,24 +14,18 @@ describe Metrics::Dashboard::SystemDashboardService, :use_clean_rails_memory_sto
   end
 
   describe 'get_dashboard' do
-    let(:dashboard_path) { described_class::SYSTEM_DASHBOARD_PATH }
+    let(:dashboard_path) { described_class::DASHBOARD_PATH }
     let(:service_params) { [project, user, { environment: environment, dashboard_path: dashboard_path }] }
     let(:service_call) { described_class.new(*service_params).get_dashboard }
 
     it_behaves_like 'valid dashboard service response'
     it_behaves_like 'raises error for users with insufficient permissions'
-
-    it 'caches the unprocessed dashboard for subsequent calls' do
-      expect(YAML).to receive(:safe_load).once.and_call_original
-
-      described_class.new(*service_params).get_dashboard
-      described_class.new(*service_params).get_dashboard
-    end
+    it_behaves_like 'caches the unprocessed dashboard for subsequent calls'
 
     context 'when called with a non-system dashboard' do
       let(:dashboard_path) { 'garbage/dashboard/path' }
 
-      # We want to alwaus return the system dashboard.
+      # We want to always return the system dashboard.
       it_behaves_like 'valid dashboard service response'
     end
   end
@@ -42,8 +36,8 @@ describe Metrics::Dashboard::SystemDashboardService, :use_clean_rails_memory_sto
 
       expect(all_dashboards).to eq(
         [{
-          path: described_class::SYSTEM_DASHBOARD_PATH,
-          display_name: described_class::SYSTEM_DASHBOARD_NAME,
+          path: described_class::DASHBOARD_PATH,
+          display_name: described_class::DASHBOARD_NAME,
           default: true,
           system_dashboard: true
         }]

spec/support/helpers/metrics_dashboard_helpers.rb

@@ -19,7 +19,7 @@ module MetricsDashboardHelpers
   end
 
   def system_dashboard_path
-    Metrics::Dashboard::SystemDashboardService::SYSTEM_DASHBOARD_PATH
+    Metrics::Dashboard::SystemDashboardService::DASHBOARD_PATH
   end
 
   def business_metric_title
@@ -53,6 +53,15 @@ module MetricsDashboardHelpers
     it_behaves_like 'valid dashboard service response for schema'
   end
 
+  shared_examples_for 'caches the unprocessed dashboard for subsequent calls' do
+    it do
+      expect(YAML).to receive(:safe_load).once.and_call_original
+
+      described_class.new(*service_params).get_dashboard
+      described_class.new(*service_params).get_dashboard
+    end
+  end
+
   shared_examples_for 'valid embedded dashboard service response' do
     let(:dashboard_schema) { JSON.parse(fixture_file('lib/gitlab/metrics/dashboard/schemas/embedded_dashboard.json')) }