Add a version number to dashboard cache key

This version number can be incremented when we update the dashboard
so that a new cache key is used. A new cache key ensures that the cache
is regenerated. The old cache key will expire automatically after 2
weeks, since that is the value of the global expires_in configuration.

app/services/metrics/dashboard/cluster_dashboard_service.rb

@@ -8,6 +8,10 @@ module Metrics
       DASHBOARD_PATH = 'config/prometheus/cluster_metrics.yml'
       DASHBOARD_NAME = 'Cluster'
 
+      # Update this value when the dashboard content is updated. This will force
+      # the cache to be regenerated.
+      DASHBOARD_VERSION = 1
+
       SEQUENCE = [
         STAGES::ClusterEndpointInserter,
         STAGES::PanelIdsInserter,
@@ -26,6 +30,12 @@ module Metrics
       def allowed?
         true
       end
+
+      private
+
+      def dashboard_version
+        DASHBOARD_VERSION
+      end
     end
   end
 end

app/services/metrics/dashboard/pod_dashboard_service.rb

@@ -5,6 +5,16 @@ module Metrics
     class PodDashboardService < ::Metrics::Dashboard::PredefinedDashboardService
       DASHBOARD_PATH = 'config/prometheus/pod_metrics.yml'
       DASHBOARD_NAME = 'Pod Health'
+
+      # Update this value when the dashboard content is updated. This will force
+      # the cache to be regenerated.
+      DASHBOARD_VERSION = 1
+
+      private
+
+      def dashboard_version
+        DASHBOARD_VERSION
+      end
     end
   end
 end

app/services/metrics/dashboard/predefined_dashboard_service.rb

@@ -32,8 +32,12 @@ module Metrics
 
       private
 
+      def dashboard_version
+        raise NotImplementedError
+      end
+
       def cache_key
-        "metrics_dashboard_#{dashboard_path}"
+        "metrics_dashboard_#{dashboard_path}_#{dashboard_version}"
       end
 
       def dashboard_path

app/services/metrics/dashboard/self_monitoring_dashboard_service.rb

@@ -8,6 +8,10 @@ module Metrics
       DASHBOARD_PATH = 'config/prometheus/self_monitoring_default.yml'
       DASHBOARD_NAME = N_('Default dashboard')
 
+      # Update this value when the dashboard content is updated. This will force
+      # the cache to be regenerated.
+      DASHBOARD_VERSION = 1
+
       SEQUENCE = [
         STAGES::CustomMetricsInserter,
         STAGES::MetricEndpointInserter,
@@ -35,6 +39,12 @@ module Metrics
           params[:dashboard_path].nil? && params[:environment]&.project&.self_monitoring?
         end
       end
+
+      private
+
+      def dashboard_version
+        DASHBOARD_VERSION
+      end
     end
   end
 end

app/services/metrics/dashboard/system_dashboard_service.rb

@@ -8,6 +8,10 @@ module Metrics
       DASHBOARD_PATH = 'config/prometheus/common_metrics.yml'
       DASHBOARD_NAME = N_('Default dashboard')
 
+      # Update this value when the dashboard content is updated. This will force
+      # the cache to be regenerated.
+      DASHBOARD_VERSION = 1
+
       SEQUENCE = [
         STAGES::CommonMetricsInserter,
         STAGES::CustomMetricsInserter,
@@ -30,6 +34,12 @@ module Metrics
           }]
         end
       end
+
+      private
+
+      def dashboard_version
+        DASHBOARD_VERSION
+      end
     end
   end
 end

spec/services/metrics/dashboard/cluster_dashboard_service_spec.rb

@@ -40,6 +40,7 @@ RSpec.describe Metrics::Dashboard::ClusterDashboardService, :use_clean_rails_mem
 
     it_behaves_like 'valid dashboard service response'
     it_behaves_like 'caches the unprocessed dashboard for subsequent calls'
+    it_behaves_like 'refreshes cache when dashboard_version is changed'
 
     context 'when called with a non-system dashboard' do
       let(:dashboard_path) { 'garbage/dashboard/path' }

spec/services/metrics/dashboard/pod_dashboard_service_spec.rb

@@ -47,6 +47,7 @@ RSpec.describe Metrics::Dashboard::PodDashboardService, :use_clean_rails_memory_
 
     it_behaves_like 'valid dashboard service response'
     it_behaves_like 'caches the unprocessed dashboard for subsequent calls'
+    it_behaves_like 'refreshes cache when dashboard_version is changed'
     it_behaves_like 'updates gitlab_metrics_dashboard_processing_time_ms metric'
   end
 end

spec/services/metrics/dashboard/self_monitoring_dashboard_service_spec.rb

@@ -32,6 +32,7 @@ RSpec.describe Metrics::Dashboard::SelfMonitoringDashboardService, :use_clean_ra
     it_behaves_like 'valid dashboard service response'
     it_behaves_like 'raises error for users with insufficient permissions'
     it_behaves_like 'caches the unprocessed dashboard for subsequent calls'
+    it_behaves_like 'refreshes cache when dashboard_version is changed'
     it_behaves_like 'updates gitlab_metrics_dashboard_processing_time_ms metric'
   end
 

spec/services/metrics/dashboard/system_dashboard_service_spec.rb

@@ -28,6 +28,7 @@ RSpec.describe Metrics::Dashboard::SystemDashboardService, :use_clean_rails_memo
     it_behaves_like 'valid dashboard service response'
     it_behaves_like 'raises error for users with insufficient permissions'
     it_behaves_like 'caches the unprocessed dashboard for subsequent calls'
+    it_behaves_like 'refreshes cache when dashboard_version is changed'
     it_behaves_like 'updates gitlab_metrics_dashboard_processing_time_ms metric'
 
     context 'when called with a non-system dashboard' do

spec/support/shared_examples/services/metrics/dashboard_shared_examples.rb

@@ -39,6 +39,22 @@ RSpec.shared_examples 'caches the unprocessed dashboard for subsequent calls' do
   end
 end
 
+# This spec is applicable for predefined/out-of-the-box dashboard services.
+RSpec.shared_examples 'refreshes cache when dashboard_version is changed' do
+  specify do
+    allow_next_instance_of(described_class) do |service|
+      allow(service).to receive(:dashboard_version).and_return(1, 2)
+    end
+
+    expect(File).to receive(:read).twice.and_call_original
+
+    service = described_class.new(*service_params)
+
+    service.get_dashboard
+    service.get_dashboard
+  end
+end
+
 RSpec.shared_examples 'valid embedded dashboard service response' do
   let(:dashboard_schema) { Gitlab::Json.parse(fixture_file('lib/gitlab/metrics/dashboard/schemas/embedded_dashboard.json')) }