Delete cache of dashboards in same project only

When a dashboard under `.gitlab/dashboards` in a project's repository
is modified, delete only that project's dashboard caches.

app/services/metrics/dashboard/base_service.rb

@@ -34,7 +34,7 @@ module Metrics
 
       # Returns an un-processed dashboard from the cache.
       def raw_dashboard
-        Gitlab::Metrics::Dashboard::Cache.fetch(cache_key) { get_raw_dashboard }
+        Gitlab::Metrics::Dashboard::Cache.for(project).fetch(cache_key) { get_raw_dashboard }
       end
 
       # Should return true if this dashboard service is for an out-of-the-box

app/services/metrics/dashboard/predefined_dashboard_service.rb

@@ -30,6 +30,11 @@ module Metrics
         end
       end
 
+      # Returns an un-processed dashboard from the cache.
+      def raw_dashboard
+        Gitlab::Metrics::Dashboard::Cache.fetch(cache_key) { get_raw_dashboard }
+      end
+
       private
 
       def dashboard_version

lib/gitlab/metrics/dashboard/cache.rb

@@ -9,8 +9,20 @@ module Gitlab
         CACHE_KEYS = 'all_cached_metric_dashboards'
 
         class << self
+          # This class method (Gitlab::Metrics::Dashboard::Cache.fetch) can be used
+          # when the key does not need to be deleted by `delete_all!`.
+          # For example, out of the box dashboard caches do not need to be deleted.
+          delegate :fetch, to: :"Rails.cache"
+
+          alias_method :for, :new
+        end
+
+        def initialize(project)
+          @project = project
+        end
+
         # Stores a dashboard in the cache, documenting the key
-          # so the cached can be cleared in bulk at another time.
+        # so the cache can be cleared in bulk at another time.
         def fetch(key)
           register_key(key)
 
@@ -23,7 +35,7 @@ module Gitlab
         def delete_all!
           all_keys.each { |key| Rails.cache.delete(key) }
 
-            Rails.cache.delete(CACHE_KEYS)
+          Rails.cache.delete(catalog_key)
         end
 
         private
@@ -31,12 +43,19 @@ module Gitlab
         def register_key(key)
           new_keys = all_keys.add(key).to_a.join('|')
 
-            Rails.cache.write(CACHE_KEYS, new_keys)
+          Rails.cache.write(catalog_key, new_keys)
         end
 
         def all_keys
-            Set.new(Rails.cache.read(CACHE_KEYS)&.split('|'))
+          keys = Rails.cache.read(catalog_key)&.split('|')
+          Set.new(keys)
         end
+
+        # One key to store them all...
+        # This key is used to store the names of all the keys that contain this
+        # project's dashboards.
+        def catalog_key
+          "#{CACHE_KEYS}_#{@project.id}"
         end
       end
     end

lib/gitlab/metrics/dashboard/repo_dashboard_finder.rb

@@ -14,7 +14,7 @@ module Gitlab
           # Also deletes all dashboard cache entries.
           # @return [Array] ex) ['.gitlab/dashboards/dashboard1.yml']
           def list_dashboards(project)
-            Gitlab::Metrics::Dashboard::Cache.delete_all!
+            Gitlab::Metrics::Dashboard::Cache.for(project).delete_all!
 
             file_finder(project).list_files_for(DASHBOARD_ROOT)
           end

spec/lib/gitlab/metrics/dashboard/cache_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe Gitlab::Metrics::Dashboard::Cache, :use_clean_rails_memory_store_caching do
+  let_it_be(:project1) { build_stubbed(:project) }
+  let_it_be(:project2) { build_stubbed(:project) }
+
+  let(:project1_key1) { "#{project1.id}_key1" }
+  let(:project1_key2) { "#{project1.id}_key2" }
+  let(:project2_key1) { "#{project2.id}_key1" }
+
+  let(:cache1) { described_class.for(project1) }
+  let(:cache2) { described_class.for(project2) }
+
+  before do
+    cache1.fetch(project1_key1) { 'data1' }
+    cache1.fetch(project1_key2) { 'data2' }
+    cache2.fetch(project2_key1) { 'data3' }
+  end
+
+  describe '.fetch' do
+    it 'stores data correctly' do
+      described_class.fetch('key1') { 'data1' }
+      described_class.fetch('key2') { 'data2' }
+
+      expect(described_class.fetch('key1')).to eq('data1')
+      expect(described_class.fetch('key2')).to eq('data2')
+    end
+  end
+
+  describe '.for' do
+    it 'returns a new instance' do
+      expect(described_class.for(project1)).to be_instance_of(described_class)
+    end
+  end
+
+  describe '#fetch' do
+    it 'stores data correctly' do
+      expect(cache1.fetch(project1_key1)).to eq('data1')
+      expect(cache1.fetch(project1_key2)).to eq('data2')
+      expect(cache2.fetch(project2_key1)).to eq('data3')
+    end
+  end
+
+  describe '#delete_all!' do
+    it 'deletes keys of the given project', :aggregate_failures do
+      cache1.delete_all!
+
+      expect(Rails.cache.exist?(project1_key1)).to be(false)
+      expect(Rails.cache.exist?(project1_key2)).to be(false)
+      expect(cache2.fetch(project2_key1)).to eq('data3')
+
+      cache2.delete_all!
+
+      expect(Rails.cache.exist?(project2_key1)).to be(false)
+    end
+
+    it 'does not fail when nothing to delete' do
+      project3 = build_stubbed(:project)
+      cache3 = described_class.for(project3)
+
+      expect { cache3.delete_all! }.not_to raise_error
+    end
+  end
+
+  context 'multiple fetches and deletes' do
+    specify :aggregate_failures do
+      cache1.delete_all!
+
+      expect(Rails.cache.exist?(project1_key1)).to be(false)
+      expect(Rails.cache.exist?(project1_key2)).to be(false)
+
+      cache1.fetch("#{project1.id}_key3") { 'data1' }
+      cache1.fetch("#{project1.id}_key4") { 'data2' }
+
+      expect(cache1.fetch("#{project1.id}_key3")).to eq('data1')
+      expect(cache1.fetch("#{project1.id}_key4")).to eq('data2')
+
+      cache1.delete_all!
+
+      expect(Rails.cache.exist?("#{project1.id}_key3")).to be(false)
+      expect(Rails.cache.exist?("#{project1.id}_key4")).to be(false)
+    end
+  end
+end

spec/lib/gitlab/metrics/dashboard/repo_dashboard_finder_spec.rb

@@ -9,7 +9,10 @@ RSpec.describe Gitlab::Metrics::Dashboard::RepoDashboardFinder do
 
   describe '.list_dashboards' do
     it 'deletes dashboard cache entries' do
-      expect(Gitlab::Metrics::Dashboard::Cache).to receive(:delete_all!).and_call_original
+      cache = instance_double(Gitlab::Metrics::Dashboard::Cache)
+      allow(Gitlab::Metrics::Dashboard::Cache).to receive(:for).and_return(cache)
+
+      expect(cache).to receive(:delete_all!)
 
       described_class.list_dashboards(project)
     end

spec/services/metrics/dashboard/custom_metric_embed_service_spec.rb

@@ -111,7 +111,8 @@ RSpec.describe Metrics::Dashboard::CustomMetricEmbedService do
       it_behaves_like 'valid embedded dashboard service response'
 
       it 'does not cache the unprocessed dashboard' do
-        expect(Gitlab::Metrics::Dashboard::Cache).not_to receive(:fetch)
+        # Fail spec if any method of Cache class is called.
+        stub_const('Gitlab::Metrics::Dashboard::Cache', double)
 
         described_class.new(*service_params).get_dashboard
       end

spec/services/metrics/dashboard/gitlab_alert_embed_service_spec.rb

@@ -87,7 +87,8 @@ RSpec.describe Metrics::Dashboard::GitlabAlertEmbedService do
       end
 
       it 'does not cache the unprocessed dashboard' do
-        expect(Gitlab::Metrics::Dashboard::Cache).not_to receive(:fetch)
+        # Fail spec if any method of Cache class is called.
+        stub_const('Gitlab::Metrics::Dashboard::Cache', double)
 
         described_class.new(*service_params).get_dashboard
       end