Inherit from BaseService

Change MetricsDashboard::Service to inherit from BaseService so that
it can reuse methods like initialize, success, error.

app/controllers/projects/environments_controller.rb

@@ -162,9 +162,19 @@ class Projects::EnvironmentsController < Projects::ApplicationController
 
     respond_to do |format|
       format.json do
-        dashboard = Gitlab::MetricsDashboard::Service.new(@project).get_dashboard
+        result = Gitlab::MetricsDashboard::Service.new(@project).get_dashboard
 
-        render json: dashboard, status: :ok
+        if result[:status] == :success
+          render status: :ok, json: {
+            status: :success,
+            dashboard: result[:dashboard]
+          }
+        else
+          render status: result[:http_status] || :bad_request, json: {
+            message: result[:message],
+            status: result[:status]
+          }
+        end
       end
     end
   end

lib/gitlab/metrics_dashboard/service.rb

@@ -3,19 +3,17 @@
 # Fetches the metrics dashboard layout and supplemented the output with DB info.
 module Gitlab
   module MetricsDashboard
-    class Service
+    class Service < ::BaseService
       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 }
+        dashboard_string = Rails.cache.fetch(cache_key) { system_dashboard }
+
+        dashboard = JSON.parse(process_dashboard(dashboard_string))
 
-        process_dashboard(dashboard)
+        success(dashboard: dashboard)
       end
 
       private

spec/controllers/projects/environments_controller_spec.rb

@@ -479,8 +479,8 @@ describe Projects::EnvironmentsController do
         get :metrics_dashboard, params: environment_params(format: :json)
 
         expect(response).to have_gitlab_http_status(:ok)
-        expect(json_response).to include('dashboard', 'order', 'panel_groups')
-        expect(json_response['panel_groups']).to all( include('group', 'priority', 'panels') )
+        expect(json_response.keys).to contain_exactly('dashboard', 'status')
+        expect(json_response['dashboard']).to be_an_instance_of(Hash)
       end
     end
   end

spec/lib/gitlab/metrics_dashboard/service_spec.rb

@@ -7,11 +7,13 @@ describe Gitlab::MetricsDashboard::Service, :use_clean_rails_memory_store_cachin
 
   describe 'get_dashboard' do
     it 'returns a json representation of the environment dashboard' do
-      dashboard = described_class.new(project).get_dashboard
-      json = JSON.parse(dashboard, symbolize_names: true)
+      result = described_class.new(project).get_dashboard
 
-      expect(json).to include(:dashboard, :order, :panel_groups)
-      expect(json[:panel_groups]).to all( include(:group, :priority, :panels) )
+      expect(result.keys).to contain_exactly(:dashboard, :status)
+      expect(result[:status]).to eq(:success)
+
+      expect(result[:dashboard]).to include('dashboard', 'order', 'panel_groups')
+      expect(result[:dashboard]['panel_groups']).to all( include('group', 'priority', 'panels') )
     end
 
     it 'caches the dashboard for subsequent calls' do