Add metrics dashboard template finder

This adds the necessary backend that manages
the *.metrics-dashboard.yml template files

app/finders/template_finder.rb

@@ -6,7 +6,8 @@ class TemplateFinder
   VENDORED_TEMPLATES = HashWithIndifferentAccess.new(
     dockerfiles: ::Gitlab::Template::DockerfileTemplate,
     gitignores: ::Gitlab::Template::GitignoreTemplate,
-    gitlab_ci_ymls: ::Gitlab::Template::GitlabCiYmlTemplate
+    gitlab_ci_ymls: ::Gitlab::Template::GitlabCiYmlTemplate,
+    metrics_dashboard_ymls: ::Gitlab::Template::MetricsDashboardTemplate
   ).freeze
 
   class << self

app/helpers/blob_helper.rb

@@ -200,6 +200,10 @@ module BlobHelper
     @gitlab_ci_ymls ||= template_dropdown_names(TemplateFinder.build(:gitlab_ci_ymls, project).execute)
   end
 
+  def metrics_dashboard_ymls(project)
+    @metrics_dashboard_ymls ||= template_dropdown_names(TemplateFinder.build(:metrics_dashboard_ymls, project).execute)
+  end
+
   def dockerfile_names(project)
     @dockerfile_names ||= template_dropdown_names(TemplateFinder.build(:dockerfiles, project).execute)
   end

doc/development/operations/metrics/templates.md

+# Development guide for Metrics Dashboards templates
+
+This document explains how to develop Metrics Dashboards templates
+
+## Place the template file in the relevant directory
+
+All template files reside in the `lib/gitlab/metrics/templates` directory
+
+## Criteria
+
+All the templates must be named with the `*.metrics-dashboard.yml` suffix.
+
+The file must follow the [custom dashboard syntax](../../../operations/metrics/dashboards/yaml.md).
+
+### Make sure the new template can be selected in the UI
+
+All the templates available in `lib/gitlab/metrics/templates` are selectable in the **New File** UI from the repository view as well from the **WebIDE** New File template selector.
+
+![Metrics dashboard template selection](img/metrics_dashboard_template_selection_v13_3.png)
+![Metrics dashboard template selection WebIDE](img/metrics_dashboard_template_selection_web_ide_v13_3.png)

ee/app/finders/ee/template_finder.rb

@@ -7,7 +7,8 @@ module EE
     CUSTOM_TEMPLATES = HashWithIndifferentAccess.new(
       dockerfiles: ::Gitlab::Template::CustomDockerfileTemplate,
       gitignores: ::Gitlab::Template::CustomGitignoreTemplate,
-      gitlab_ci_ymls: ::Gitlab::Template::CustomGitlabCiYmlTemplate
+      gitlab_ci_ymls: ::Gitlab::Template::CustomGitlabCiYmlTemplate,
+      metrics_dashboard_ymls: ::Gitlab::Template::MetricsDashboardTemplate
     ).freeze
 
     attr_reader :custom_templates

lib/api/project_templates.rb

@@ -4,7 +4,7 @@ module API
   class ProjectTemplates < Grape::API::Instance
     include PaginationParams
 
-    TEMPLATE_TYPES = %w[dockerfiles gitignores gitlab_ci_ymls licenses].freeze
+    TEMPLATE_TYPES = %w[dockerfiles gitignores gitlab_ci_ymls licenses metrics_dashboard_ymls].freeze
     # The regex is needed to ensure a period (e.g. agpl-3.0)
     # isn't confused with a format type. We also need to allow encoded
     # values (e.g. C%2B%2B for C++), so allow % and + as well.
@@ -14,7 +14,7 @@ module API
 
     params do
       requires :id, type: String, desc: 'The ID of a project'
-      requires :type, type: String, values: TEMPLATE_TYPES, desc: 'The type (dockerfiles|gitignores|gitlab_ci_ymls|licenses) of the template'
+      requires :type, type: String, values: TEMPLATE_TYPES, desc: 'The type (dockerfiles|gitignores|gitlab_ci_ymls|licenses|metrics_dashboard_ymls) of the template'
     end
     resource :projects, requirements: API::NAMESPACE_OR_PROJECT_REQUIREMENTS do
       desc 'Get a list of templates available to this project' do

lib/gitlab/metrics/templates/Default.metrics-dashboard.yml

+# Only one dashboard should be defined per file
+# More info: https://docs.gitlab.com/ee/operations/metrics/dashboards/yaml.html
+dashboard: 'Single Stat'
+
+# This is where all of the variables that can be manipulated via the UI
+# are initialized
+# Check out: https://docs.gitlab.com/ee/operations/metrics/dashboards/templating_variables.html#templating-variables-for-metrics-dashboards-core
+templating:
+  variables:
+    job: 'prometheus'
+
+# For more information about the required properties of panel_groups
+# please visit: https://docs.gitlab.com/ee/operations/metrics/dashboards/yaml.html#panel-group-panel_groups-properties
+panel_groups:
+  - group: 'Memory'
+    panels:
+      - title: Prometheus
+        type: single-stat
+        metrics:
+            # Queries that make use of variables need to have double curly brackets {}
+            # set to the variables, per the example below
+            query: 'max(go_memstats_alloc_bytes{job="{{job}}"}) / 1024 /1024'
+            unit: '%'
+            label: "Max"

lib/gitlab/metrics/templates/index.md

+# Development guide for Metrics Dashboard templates
+
+Please follow [the development guideline](../../../../doc/development/operations/metrics/templates.md)

lib/gitlab/template/metrics_dashboard_template.rb

+# frozen_string_literal: true
+
+module Gitlab
+  module Template
+    class MetricsDashboardTemplate < BaseTemplate
+      def content
+        explanation = "# This file is a template, and might need editing before it works on your project."
+        [explanation, super].join("\n")
+      end
+
+      class << self
+        def extension
+          '.metrics-dashboard.yml'
+        end
+
+        def categories
+          {
+            "General" => ''
+          }
+        end
+
+        def base_dir
+          Rails.root.join('lib/gitlab/metrics/templates')
+        end
+
+        def finder(project = nil)
+          Gitlab::Template::Finders::GlobalTemplateFinder.new(self.base_dir, self.extension, self.categories)
+        end
+      end
+    end
+  end
+end

spec/lib/gitlab/template/metrics_dashboard_template_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe Gitlab::Template::MetricsDashboardTemplate do
+  subject { described_class }
+
+  describe '.all' do
+    it 'strips the metrics-dashboard suffix' do
+      expect(subject.all.first.name).not_to end_with('metrics-dashboard.yml')
+    end
+
+    it 'combines the globals and rest' do
+      all = subject.all.map(&:name)
+
+      expect(all).to include('Default')
+    end
+
+    it 'ensures that the template name is used exactly once' do
+      all = subject.all.group_by(&:name)
+      duplicates = all.select { |_, templates| templates.length > 1 }
+
+      expect(duplicates).to be_empty
+    end
+  end
+
+  describe '.find' do
+    it 'returns nil if the file does not exist' do
+      expect(subject.find('nonexistent-file')).to be nil
+    end
+
+    it 'returns the MetricsDashboardYml object of a valid file' do
+      default_dashboard = subject.find('Default')
+
+      expect(default_dashboard).to be_a described_class
+      expect(default_dashboard.name).to eq('Default')
+    end
+  end
+
+  describe '.by_category' do
+    it 'returns sorted results' do
+      result = described_class.by_category('General')
+
+      expect(result).to eq(result.sort)
+    end
+  end
+
+  describe '#content' do
+    it 'loads the full file' do
+      example_dashboard = subject.new(Rails.root.join('lib/gitlab/metrics/templates/Default.metrics-dashboard.yml'))
+
+      expect(example_dashboard.name).to eq 'Default'
+      expect(example_dashboard.content).to start_with('#')
+    end
+  end
+
+  describe '#<=>' do
+    it 'sorts lexicographically' do
+      one = described_class.new('a.metrics-dashboard.yml')
+      other = described_class.new('z.metrics-dashboard.yml')
+
+      expect(one.<=>(other)).to be(-1)
+      expect([other, one].sort).to eq([one, other])
+    end
+  end
+end

spec/requests/api/project_templates_spec.rb

@@ -62,6 +62,15 @@ RSpec.describe API::ProjectTemplates do
       expect(json_response).to satisfy_one { |template| template['key'] == 'mit' }
     end
 
+    it 'returns metrics_dashboard_ymls' do
+      get api("/projects/#{public_project.id}/templates/metrics_dashboard_ymls")
+
+      expect(response).to have_gitlab_http_status(:ok)
+      expect(response).to include_pagination_headers
+      expect(response).to match_response_schema('public_api/v4/template_list')
+      expect(json_response).to satisfy_one { |template| template['key'] == 'Default' }
+    end
+
     it 'returns 400 for an unknown template type' do
       get api("/projects/#{public_project.id}/templates/unknown")
 
@@ -136,6 +145,14 @@ RSpec.describe API::ProjectTemplates do
       expect(json_response['name']).to eq('Android')
     end
 
+    it 'returns a specific metrics_dashboard_yml' do
+      get api("/projects/#{public_project.id}/templates/metrics_dashboard_ymls/Default")
+
+      expect(response).to have_gitlab_http_status(:ok)
+      expect(response).to match_response_schema('public_api/v4/template')
+      expect(json_response['name']).to eq('Default')
+    end
+
     it 'returns a specific license' do
       get api("/projects/#{public_project.id}/templates/licenses/mit")
 
@@ -166,6 +183,10 @@ RSpec.describe API::ProjectTemplates do
       subject { get api("/projects/#{url_encoded_path}/templates/gitlab_ci_ymls/Android") }
     end
 
+    it_behaves_like 'accepts project paths with dots' do
+      subject { get api("/projects/#{url_encoded_path}/templates/metrics_dashboard_ymls/Default") }
+    end
+
     shared_examples 'path traversal attempt' do |template_type|
       it 'rejects invalid filenames' do
         get api("/projects/#{public_project.id}/templates/#{template_type}/%2e%2e%2fPython%2ea")