Show multimetric embeds on a single chart

When several user-defined prometheus metrics exist with
the same group, title, and y-axis label, they are grouped
onto a single panel. This change updated embeds to also
display these metrics on a single panel, rather than
separating them out one metric per panel.

app/services/metrics/dashboard/custom_metric_embed_service.rb

@@ -57,7 +57,7 @@ module Metrics
       # @return [Hash]
       override :raw_dashboard
       def raw_dashboard
-        panels_not_found!(identifiers) if panels.empty?
+        panels_not_found!(identifiers) if metrics.empty?
 
         { 'panel_groups' => [{ 'panels' => panels }] }
       end
@@ -66,11 +66,20 @@ module Metrics
 
       # Generated dashboard panels for each metric which
       # matches the provided input.
+      #
+      # As the panel is generated
+      # on the fly, we're using default values for info
+      # not represented in the DB.
+      #
       # @return [Array<Hash>]
       def panels
-        strong_memoize(:panels) do
-          metrics.map { |metric| panel_for_metric(metric) }
-        end
+        [{
+          type: DEFAULT_PANEL_TYPE,
+          weight: DEFAULT_PANEL_WEIGHT,
+          title: title,
+          y_label: y_label,
+          metrics: metrics.map(&:to_metric_hash)
+        }]
       end
 
       # Metrics which match the provided inputs.
@@ -78,12 +87,14 @@ module Metrics
       # displayed in a single panel/chart.
       # @return [ActiveRecord::AssociationRelation<PromtheusMetric>]
       def metrics
-        PrometheusMetricsFinder.new(
-          project: project,
-          group: group_key,
-          title: title,
-          y_label: y_label
-        ).execute
+        strong_memoize(:metrics) do
+          PrometheusMetricsFinder.new(
+            project: project,
+            group: group_key,
+            title: title,
+            y_label: y_label
+          ).execute
+        end
       end
 
       # Returns a symbol representing the group that
@@ -101,22 +112,6 @@ module Metrics
             .to_s
         end
       end
-
-      # Returns a representation of a PromtheusMetric
-      # as a dashboard panel. As the panel is generated
-      # on the fly, we're using default values for info
-      # not represented in the DB.
-      #
-      # @return [Hash]
-      def panel_for_metric(metric)
-        {
-          type: DEFAULT_PANEL_TYPE,
-          weight: DEFAULT_PANEL_WEIGHT,
-          title: metric.title,
-          y_label: metric.y_label,
-          metrics: [metric.to_metric_hash]
-        }
-      end
     end
   end
 end

changelogs/unreleased/sy-fix-multi-metric-embed.yml

+---
+title: Show multimetric embeds on a single chart
+merge_request: 28841
+author:
+type: fixed

spec/services/metrics/dashboard/custom_metric_embed_service_spec.rb

@@ -121,11 +121,18 @@ describe Metrics::Dashboard::CustomMetricEmbedService do
 
         it_behaves_like 'valid embedded dashboard service response'
 
-        it 'includes both metrics' do
+        it 'includes both metrics in a single panel' do
           result = service_call
-          included_queries = all_queries(result[:dashboard])
 
-          expect(included_queries).to include('avg(metric_2)', 'avg(metric)')
+          panel_groups = result[:dashboard][:panel_groups]
+          panels = panel_groups[0][:panels]
+          metrics = panels[0][:metrics]
+          queries = metrics.map { |metric| metric[:query_range] }
+
+          expect(panel_groups.length).to eq(1)
+          expect(panels.length).to eq(1)
+          expect(metrics.length).to eq(2)
+          expect(queries).to include('avg(metric_2)', 'avg(metric)')
         end
       end
     end
@@ -136,16 +143,4 @@ describe Metrics::Dashboard::CustomMetricEmbedService do
       it_behaves_like 'misconfigured dashboard service response', :not_found
     end
   end
-
-  private
-
-  def all_queries(dashboard)
-    dashboard[:panel_groups].flat_map do |group|
-      group[:panels].flat_map do |panel|
-        panel[:metrics].map do |metric|
-          metric[:query_range]
-        end
-      end
-    end
-  end
 end