Add Panel Preview service

To process user supplied metrics dashboard panel yaml
we need to add new service to process it.

app/controllers/projects/metrics/dashboards/builder_controller.rb

@@ -9,7 +9,13 @@ module Projects
 
         def panel_preview
           respond_to do |format|
-            format.json { render json: render_panel }
+            format.json do
+              if rendered_panel.success?
+                render json: rendered_panel.payload
+              else
+                render json: { message: rendered_panel.message }, status: :unprocessable_entity
+              end
+            end
           end
         end
 
@@ -19,25 +25,21 @@ module Projects
           render_404 unless Feature.enabled?(:metrics_dashboard_new_panel_page, project)
         end
 
-        def render_panel
-          {
-            "title": "Memory Usage (Total)",
-            "type": "area-chart",
-            "y_label": "Total Memory Used (GB)",
-            "weight": 4,
-            "metrics": [
-              {
-                "id": "system_metrics_kubernetes_container_memory_total",
-                "query_range": "avg(sum(container_memory_usage_bytes{container_name!=\"POD\",pod_name=~\"^{{ci_environment_slug}}-(.*)\",namespace=\"{{kube_namespace}}\"}) by (job)) without (job)  /1024/1024/1024",
-                "label": "Total (GB)",
-                "unit": "GB",
-                "metric_id": 15,
-                "edit_path": nil,
-                "prometheus_endpoint_path": "/root/autodevops-deploy/-/environments/29/prometheus/api/v1/query_range?query=avg%28sum%28container_memory_usage_bytes%7Bcontainer_name%21%3D%22POD%22%2Cpod_name%3D~%22%5E%7B%7Bci_environment_slug%7D%7D-%28.%2A%29%22%2Cnamespace%3D%22%7B%7Bkube_namespace%7D%7D%22%7D%29+by+%28job%29%29+without+%28job%29++%2F1024%2F1024%2F1024"
-              }
-            ],
-            "id": "4570deed516d0bf93fb42879004117009ab456ced27393ec8dce5b6960438132"
-          }
+        def rendered_panel
+          @panel_preview ||= ::Metrics::Dashboard::PanelPreviewService.new(project, panel_yaml, environment).execute
+        end
+
+        def panel_yaml
+          params.require(:panel_yaml)
+        end
+
+        def environment
+          @environment ||=
+            if params[:environment]
+              project.environments.find(params[:environment])
+            else
+              project.default_environment
+            end
         end
       end
     end

app/services/metrics/dashboard/panel_preview_service.rb

+# frozen_string_literal: true
+
+# Ingest YAML fragment with metrics dashboard panel definition
+# https://docs.gitlab.com/ee/operations/metrics/dashboards/yaml.html#panel-panels-properties
+# process it and returns renderable json version
+module Metrics
+  module Dashboard
+    class PanelPreviewService
+      SEQUENCE = [
+        ::Gitlab::Metrics::Dashboard::Stages::CommonMetricsInserter,
+        ::Gitlab::Metrics::Dashboard::Stages::MetricEndpointInserter,
+        ::Gitlab::Metrics::Dashboard::Stages::PanelIdsInserter,
+        ::Gitlab::Metrics::Dashboard::Stages::AlertsInserter,
+        ::Gitlab::Metrics::Dashboard::Stages::UrlValidator
+      ].freeze
+
+      HANDLED_PROCESSING_ERRORS = [
+        Gitlab::Metrics::Dashboard::Errors::DashboardProcessingError,
+        Gitlab::Config::Loader::Yaml::NotHashError,
+        Gitlab::Config::Loader::Yaml::DataTooLargeError,
+        Gitlab::Config::Loader::FormatError
+      ].freeze
+
+      def initialize(project, panel_yaml, environment)
+        @project, @panel_yaml, @environment = project, panel_yaml, environment
+      end
+
+      def execute
+        dashboard = ::Gitlab::Metrics::Dashboard::Processor.new(project, dashboard_structure, SEQUENCE, environment: environment).process
+        ServiceResponse.success(payload: dashboard[:panel_groups][0][:panels][0])
+      rescue *HANDLED_PROCESSING_ERRORS => error
+        ServiceResponse.error(message: error.message)
+      end
+
+      private
+
+      attr_accessor :project, :panel_yaml, :environment
+
+      def dashboard_structure
+        {
+          panel_groups: [
+            {
+              panels: [panel_hash]
+            }
+          ]
+        }
+      end
+
+      def panel_hash
+        ::Gitlab::Config::Loader::Yaml.new(panel_yaml).load_raw!
+      end
+    end
+  end
+end

spec/requests/projects/metrics/dashboards/builder_spec.rb

@@ -6,6 +6,42 @@ RSpec.describe 'Projects::Metrics::Dashboards::BuilderController' do
   let_it_be(:project) { create(:project) }
   let_it_be(:environment) { create(:environment, project: project) }
   let_it_be(:user) { create(:user) }
+  let_it_be(:valid_panel_yml) do
+    <<~YML
+    ---
+    title: "Super Chart A1"
+    type: "area-chart"
+    y_label: "y_label"
+    weight: 1
+    max_value: 1
+    metrics:
+    - id: metric_a1
+      query_range: |+
+        avg(
+          sum(
+            container_memory_usage_bytes{
+              container_name!="POD",
+              pod_name=~"^{{ci_environment_slug}}-(.*)",
+              namespace="{{kube_namespace}}",
+              user_def_variable="{{user_def_variable}}"
+            }
+          ) by (job)
+        ) without (job)
+        /1024/1024/1024
+      unit: unit
+      label: Legend Label
+    YML
+  end
+  let_it_be(:invalid_panel_yml) do
+    <<~YML
+    ---
+    title: "Super Chart A1"
+    type: "area-chart"
+    y_label: "y_label"
+    weight: 1
+    max_value: 1
+    YML
+  end
 
   def send_request(params = {})
     post namespace_project_metrics_dashboards_builder_path(namespace_id: project.namespace, project_id: project, format: :json, **params)
@@ -17,14 +53,14 @@ RSpec.describe 'Projects::Metrics::Dashboards::BuilderController' do
         stub_feature_flags(metrics_dashboard_new_panel_page: true)
       end
 
-      it 'redirects to sign in' do
+      it 'redirects user to sign in page' do
         send_request
 
         expect(response).to redirect_to(new_user_session_path)
       end
     end
 
-    context 'as user with reporter access' do
+    context 'as user with guest access' do
       before do
         stub_feature_flags(metrics_dashboard_new_panel_page: true)
         project.add_guest(user)
@@ -49,10 +85,31 @@ RSpec.describe 'Projects::Metrics::Dashboards::BuilderController' do
           stub_feature_flags(metrics_dashboard_new_panel_page: true)
         end
 
-        it 'returns success' do
-          send_request
+        context 'valid yaml panel is supplied' do
+          it 'returns success' do
+            send_request(panel_yaml: valid_panel_yml)
+
+            expect(response).to have_gitlab_http_status(:ok)
+            expect(json_response).to include('title' => 'Super Chart A1', 'type' => 'area-chart')
+          end
+        end
+
+        context 'invalid yaml panel is supplied' do
+          it 'returns unprocessable entity' do
+            send_request(panel_yaml: invalid_panel_yml)
+
+            expect(response).to have_gitlab_http_status(:unprocessable_entity)
+            expect(json_response['message']).to eq('Each "panel" must define an array :metrics')
+          end
+        end
+
+        context 'invalid panel_yaml is not a yaml string' do
+          it 'returns unprocessable entity' do
+            send_request(panel_yaml: 1)
 
-          expect(response).to have_gitlab_http_status(:ok)
+            expect(response).to have_gitlab_http_status(:unprocessable_entity)
+            expect(json_response['message']).to eq('Invalid configuration format')
+          end
         end
       end
 

spec/services/metrics/dashboard/panel_preview_service_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe Metrics::Dashboard::PanelPreviewService do
+  let_it_be(:project) { create(:project) }
+  let_it_be(:environment) { create(:environment, project: project) }
+  let_it_be(:panel_yml) do
+    <<~YML
+    ---
+    title: test panel
+    YML
+  end
+  let_it_be(:dashboard) do
+    {
+      panel_groups: [
+        {
+          panels: [{ 'title' => 'test panel' }]
+        }
+      ]
+    }
+  end
+
+  describe '#execute' do
+    subject(:service_response) { described_class.new(project, panel_yml, environment).execute }
+
+    context "valid panel's yaml" do
+      before do
+        allow_next_instance_of(::Gitlab::Metrics::Dashboard::Processor) do |processor|
+          allow(processor).to receive(:process).and_return(dashboard)
+        end
+      end
+
+      it 'returns success service response' do
+        expect(service_response.success?).to be_truthy
+      end
+
+      it 'returns processed panel' do
+        expect(service_response.payload).to eq('title' => 'test panel')
+      end
+
+      it 'uses dashboard processor' do
+        sequence = [
+          ::Gitlab::Metrics::Dashboard::Stages::CommonMetricsInserter,
+          ::Gitlab::Metrics::Dashboard::Stages::MetricEndpointInserter,
+          ::Gitlab::Metrics::Dashboard::Stages::PanelIdsInserter,
+          ::Gitlab::Metrics::Dashboard::Stages::AlertsInserter,
+          ::Gitlab::Metrics::Dashboard::Stages::UrlValidator
+        ]
+        processor_params = [project, dashboard, sequence, environment: environment]
+
+        expect_next_instance_of(::Gitlab::Metrics::Dashboard::Processor, *processor_params) do |processor|
+          expect(processor).to receive(:process).and_return(dashboard)
+        end
+
+        service_response
+      end
+    end
+
+    context "invalid  panel's yaml" do
+      [
+        Gitlab::Metrics::Dashboard::Errors::DashboardProcessingError,
+        Gitlab::Config::Loader::Yaml::NotHashError,
+        Gitlab::Config::Loader::Yaml::DataTooLargeError,
+        Gitlab::Config::Loader::FormatError
+      ].each do |error_class|
+        before do
+          allow_next_instance_of(::Gitlab::Metrics::Dashboard::Processor) do |processor|
+            allow(processor).to receive(:process).and_raise(error_class.new('error'))
+          end
+        end
+
+        it 'returns error service response' do
+          expect(service_response.error?).to be_truthy
+        end
+
+        it 'returns error message' do
+          expect(service_response.message).to eq('error')
+        end
+      end
+    end
+  end
+end