Refactor dashboard proccesing into stages

5 files changed, 185 insertions, 0 deletions

diff --git a/lib/gitlab/metrics_dashboard/common_metrics_inserter.rb b/lib/gitlab/metrics_dashboard/common_metrics_inserter.rb
new file mode 100644
index 00000000000..5bc83e6266e
--- /dev/null
+++ b/lib/gitlab/metrics_dashboard/common_metrics_inserter.rb
@@ -0,0 +1,32 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module MetricsDashboard
+    class CommonMetricsInserter
+      class << self
+        # For each metric in the dashboard config, attempts to find a corresponding
+        # database record. If found, includes the record's id in the dashboard config.
+        def transform!(dashboard, _project)
+          common_metrics = ::PrometheusMetric.common
+
+          for_metrics(dashboard) do |metric|
+            metric_record = common_metrics.find { |m| m.identifier == metric[:id] }
+            metric[:metric_id] = metric_record.id if metric_record
+          end
+        end
+
+        private
+
+        def for_metrics(dashboard)
+          dashboard[:panel_groups].each do |panel_group|
+            panel_group[:panels].each do |panel|
+              panel[:metrics].each do |metric|
+                yield metric
+              end
+            end
+          end
+        end
+      end
+    end
+  end
+end
diff --git a/lib/gitlab/metrics_dashboard/processor.rb b/lib/gitlab/metrics_dashboard/processor.rb
new file mode 100644
index 00000000000..9e254aa2b37
--- /dev/null
+++ b/lib/gitlab/metrics_dashboard/processor.rb
@@ -0,0 +1,20 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module MetricsDashboard
+    class Processor
+      STAGES = [CommonMetricsInserter, Sorter, ProjectMetricsInserter]
+
+      def initialize(dashboard, project)
+        @dashboard = dashboard.deep_transform_keys(&:to_sym)
+        @project = project
+      end
+
+      def process
+        STAGES.each { |stage| stage.transform!(@dashboard, @project) }
+
+        @dashboard.to_json
+      end
+    end
+  end
+end
diff --git a/lib/gitlab/metrics_dashboard/project_metrics_inserter.rb b/lib/gitlab/metrics_dashboard/project_metrics_inserter.rb
new file mode 100644
index 00000000000..67300c79e57
--- /dev/null
+++ b/lib/gitlab/metrics_dashboard/project_metrics_inserter.rb
@@ -0,0 +1,70 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module MetricsDashboard
+    class ProjectMetricsInserter
+      DEFAULT_PANEL_TYPE = 'area-chart'
+
+      class << self
+        # Inserts project-specific metrics into the dashboard config.
+        # If there are no project-specific metrics, this will have no effect.
+        def transform!(dashboard, project)
+          project.prometheus_metrics.each do |project_metric|
+            group = find_or_create(:panel_group, dashboard[:panel_groups], project_metric)
+            panel = find_or_create(:panel, group[:panels], project_metric)
+            find_or_create(:metric, panel[:metrics], project_metric)
+          end
+        end
+
+        # Looks for an instance of the named resource corresponding to the provided
+        # metric object. If unavailable, inserts one.
+        # @param name [Symbol, String] One of :panel_group, :panel, or :metric
+        # @param existing_resources [Array<Hash>]
+        # @param metric [PrometheusMetric]
+        def find_or_create(name, existing_resources, metric)
+          target = self.send("find_#{name}", existing_resources, metric)
+          return target if target
+
+          target = self.send("new_#{name}", metric)
+          existing_resources << target
+
+          target
+        end
+
+        def find_panel_group(panel_groups, metric)
+          panel_groups.find { |group| group[:group] == metric.group_title }
+        end
+
+        def find_panel(panels, metric)
+          panel_identifiers = [DEFAULT_PANEL_TYPE, metric.title, metric.y_label]
+          target_panel = panels.find { |panel| panel.values_at(:type, :title, :y_label) == panel_identifiers }
+        end
+
+        def find_metric(metrics, metric)
+          metrics.find { |m| m[:id] == metric.identifier }
+        end
+
+        def new_panel_group(metric)
+          {
+            group: metric.group_title,
+            priority: metric.priority,
+            panels: []
+          }
+        end
+
+        def new_panel(metric)
+          {
+            type: DEFAULT_PANEL_TYPE,
+            title: metric.title,
+            y_label: metric.y_label,
+            metrics: []
+          }
+        end
+
+        def new_metric(metric)
+          metric.queries.first.merge(metric_id: metric.id)
+        end
+      end
+    end
+  end
+end
diff --git a/lib/gitlab/metrics_dashboard/service.rb b/lib/gitlab/metrics_dashboard/service.rb
new file mode 100644
index 00000000000..22e1771cbea
--- /dev/null
+++ b/lib/gitlab/metrics_dashboard/service.rb
@@ -0,0 +1,37 @@
+# frozen_string_literal: true
+
+# Fetches the metrics dashboard layout and supplemented the output with DB info.
+module Gitlab
+  module MetricsDashboard
+    class Service
+      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 }
+
+        process_dashboard(dashboard)
+      end
+
+      private
+
+      # Returns the base metrics shipped with every GitLab service.
+      def system_dashboard
+        YAML.load_file(SYSTEM_DASHBOARD_PATH)
+      end
+
+      def cache_key
+        "metrics_dashboard_#{SYSTEM_DASHBOARD_NAME}"
+      end
+
+      def process_dashboard(dashboard)
+        Processor.new(dashboard, @project).process
+      end
+    end
+  end
+end
diff --git a/lib/gitlab/metrics_dashboard/sorter.rb b/lib/gitlab/metrics_dashboard/sorter.rb
new file mode 100644
index 00000000000..ba30c1e4656
--- /dev/null
+++ b/lib/gitlab/metrics_dashboard/sorter.rb
@@ -0,0 +1,26 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module MetricsDashboard
+    class Sorter
+      class << self
+        def transform!(dashboard, _project)
+          sort_groups!(dashboard)
+          sort_panels!(dashboard)
+        end
+
+        # Sorts the groups in the dashboard by the :priority key
+        def sort_groups!(dashboard)
+          dashboard[:panel_groups] = dashboard[:panel_groups].sort_by { |group| group[:priority] }
+        end
+
+        # Sorts the panels in the dashboard by the :weight key
+        def sort_panels!(dashboard)
+          dashboard[:panel_groups].each do |group|
+            group[:panels] = group[:panels].sort_by { |panel| panel[:weight] }
+          end
+        end
+      end
+    end
+  end
+end