Move BaseService to Services directory

In preparation for embedding specific metrics in issues
https://gitlab.com/gitlab-org/gitlab-ce/issues/62971,
this commit moves the BaseService for metrics dashboards
to a new services subdirectory. This is purely for the sake
of organization and maintainability.

4 files changed, 228 insertions, 0 deletions

diff --git a/app/services/metrics/dashboard/base_service.rb b/app/services/metrics/dashboard/base_service.rb
new file mode 100644
index 00000000000..b331bf51874
--- /dev/null
+++ b/app/services/metrics/dashboard/base_service.rb
@@ -0,0 +1,70 @@
+# frozen_string_literal: true
+
+# Searches a projects repository for a metrics dashboard and formats the output.
+# Expects any custom dashboards will be located in `.gitlab/dashboards`
+module Metrics
+  module Dashboard
+    class BaseService < ::BaseService
+      PROCESSING_ERROR = Gitlab::Metrics::Dashboard::Stages::BaseStage::DashboardProcessingError
+      NOT_FOUND_ERROR = Gitlab::Template::Finders::RepoTemplateFinder::FileNotFoundError
+
+      def get_dashboard
+        return error('Insufficient permissions.', :unauthorized) unless allowed?
+
+        success(dashboard: process_dashboard)
+      rescue NOT_FOUND_ERROR
+        error("#{dashboard_path} could not be found.", :not_found)
+      rescue PROCESSING_ERROR => e
+        error(e.message, :unprocessable_entity)
+      end
+
+      # Summary of all known dashboards for the service.
+      # @return [Array<Hash>] ex) [{ path: String, default: Boolean }]
+      def self.all_dashboard_paths(_project)
+        raise NotImplementedError
+      end
+
+      # Returns an un-processed dashboard from the cache.
+      def raw_dashboard
+        Gitlab::Metrics::Dashboard::Cache.fetch(cache_key) { get_raw_dashboard }
+      end
+
+      private
+
+      # Determines whether users should be able to view
+      # dashboards at all.
+      def allowed?
+        Ability.allowed?(current_user, :read_environment, project)
+      end
+
+      # Returns a new dashboard Hash, supplemented with DB info
+      def process_dashboard
+        Gitlab::Metrics::Dashboard::Processor
+          .new(project, params[:environment], raw_dashboard)
+          .process(insert_project_metrics: insert_project_metrics?)
+      end
+
+      # @return [String] Relative filepath of the dashboard yml
+      def dashboard_path
+        params[:dashboard_path]
+      end
+
+      # @return [Hash] an unmodified dashboard
+      def get_raw_dashboard
+        raise NotImplementedError
+      end
+
+      # @return [String]
+      def cache_key
+        raise NotImplementedError
+      end
+
+      # Determines whether custom metrics should be included
+      # in the processed output.
+      # @return [Boolean]
+      def insert_project_metrics?
+        false
+      end
+    end
+  end
+end
diff --git a/app/services/metrics/dashboard/default_embed_service.rb b/app/services/metrics/dashboard/default_embed_service.rb
new file mode 100644
index 00000000000..0967c5bcfeb
--- /dev/null
+++ b/app/services/metrics/dashboard/default_embed_service.rb
@@ -0,0 +1,63 @@
+# frozen_string_literal: true
+
+# Responsible for returning a filtered system dashboard
+# containing only the default embedded metrics. In future,
+# this class may be updated to support filtering to
+# alternate metrics/panels.
+#
+# Why isn't this filtering in a processing stage? By filtering
+# here, we ensure the dynamically-determined dashboard is cached.
+#
+# Use Gitlab::Metrics::Dashboard::Finder to retrive dashboards.
+module Metrics
+  module Dashboard
+    class DefaultEmbedService < ::Metrics::Dashboard::BaseService
+      # For the default filtering for embedded metrics,
+      # uses the 'id' key in dashboard-yml definition for
+      # identification.
+      DEFAULT_EMBEDDED_METRICS_IDENTIFIERS = %w(
+        system_metrics_kubernetes_container_memory_total
+        system_metrics_kubernetes_container_cores_total
+      ).freeze
+
+      # Returns a new dashboard with only the matching
+      # metrics from the system dashboard, stripped of groups.
+      # @return [Hash]
+      def raw_dashboard
+        panels = panel_groups.each_with_object([]) do |group, panels|
+          matched_panels = group['panels'].select { |panel| matching_panel?(panel) }
+
+          panels.concat(matched_panels)
+        end
+
+        { 'panel_groups' => [{ 'panels' => panels }] }
+      end
+
+      def cache_key
+        "dynamic_metrics_dashboard_#{metric_identifiers.join('_')}"
+      end
+
+      private
+
+      # Returns an array of the panels groups on the
+      # system dashboard
+      def panel_groups
+        ::Metrics::Dashboard::SystemDashboardService
+          .new(project, nil)
+          .raw_dashboard['panel_groups']
+      end
+
+      # Identifies a panel as "matching" if any metric ids in
+      # the panel is in the list of identifiers to collect.
+      def matching_panel?(panel)
+        panel['metrics'].any? do |metric|
+          metric_identifiers.include?(metric['id'])
+        end
+      end
+
+      def metric_identifiers
+        DEFAULT_EMBEDDED_METRICS_IDENTIFIERS
+      end
+    end
+  end
+end
diff --git a/app/services/metrics/dashboard/project_dashboard_service.rb b/app/services/metrics/dashboard/project_dashboard_service.rb
new file mode 100644
index 00000000000..756d387c0e6
--- /dev/null
+++ b/app/services/metrics/dashboard/project_dashboard_service.rb
@@ -0,0 +1,48 @@
+# frozen_string_literal: true
+
+# Searches a projects repository for a metrics dashboard and formats the output.
+# Expects any custom dashboards will be located in `.gitlab/dashboards`
+# Use Gitlab::Metrics::Dashboard::Finder to retrive dashboards.
+module Metrics
+  module Dashboard
+    class ProjectDashboardService < ::Metrics::Dashboard::BaseService
+      DASHBOARD_ROOT = ".gitlab/dashboards"
+
+      class << self
+        def all_dashboard_paths(project)
+          file_finder(project)
+            .list_files_for(DASHBOARD_ROOT)
+            .map do |filepath|
+              {
+                path: filepath,
+                display_name: name_for_path(filepath),
+                default: false
+              }
+            end
+        end
+
+        def file_finder(project)
+          Gitlab::Template::Finders::RepoTemplateFinder.new(project, DASHBOARD_ROOT, '.yml')
+        end
+
+        # Grabs the filepath after the base directory.
+        def name_for_path(filepath)
+          filepath.delete_prefix("#{DASHBOARD_ROOT}/")
+        end
+      end
+
+      private
+
+      # Searches the project repo for a custom-defined dashboard.
+      def get_raw_dashboard
+        yml = self.class.file_finder(project).read(dashboard_path)
+
+        YAML.safe_load(yml)
+      end
+
+      def cache_key
+        "project_#{project.id}_metrics_dashboard_#{dashboard_path}"
+      end
+    end
+  end
+end
diff --git a/app/services/metrics/dashboard/system_dashboard_service.rb b/app/services/metrics/dashboard/system_dashboard_service.rb
new file mode 100644
index 00000000000..fcd71aadb03
--- /dev/null
+++ b/app/services/metrics/dashboard/system_dashboard_service.rb
@@ -0,0 +1,47 @@
+# frozen_string_literal: true
+
+# Fetches the system metrics dashboard and formats the output.
+# Use Gitlab::Metrics::Dashboard::Finder to retrive dashboards.
+module Metrics
+  module Dashboard
+    class SystemDashboardService < ::Metrics::Dashboard::BaseService
+      SYSTEM_DASHBOARD_PATH = 'config/prometheus/common_metrics.yml'
+      SYSTEM_DASHBOARD_NAME = 'Default'
+
+      class << self
+        def all_dashboard_paths(_project)
+          [{
+            path: SYSTEM_DASHBOARD_PATH,
+            display_name: SYSTEM_DASHBOARD_NAME,
+            default: true
+          }]
+        end
+
+        def system_dashboard?(filepath)
+          filepath == SYSTEM_DASHBOARD_PATH
+        end
+      end
+
+      private
+
+      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 cache_key
+        "metrics_dashboard_#{dashboard_path}"
+      end
+
+      def insert_project_metrics?
+        true
+      end
+    end
+  end
+end