Flush statistics cache anytime it is updated

`Projects::UpdateStatisticsService` attempts to refresh project
statistics, but it relies the caller to flush the existing statistics
cache for the repository. If the flush doesn't happen, the refresh won't
actually do anything. For example, this might be happening in
`ProjectCacheWorker`.

We now expire the stats inside the service to ensure consistent results.

This came out of
https://gitlab.com/gitlab-org/gitlab/-/issues/255001.

https://gitlab.com/gitlab-org/gitlab/-/merge_requests/52938

app/services/projects/update_statistics_service.rb

@@ -2,18 +2,49 @@
 
 module Projects
   class UpdateStatisticsService < BaseService
+    include ::Gitlab::Utils::StrongMemoize
+
+    STAT_TO_CACHED_METHOD = {
+      repository_size: :size,
+      commit_count: :commit_count
+    }.freeze
+
     def execute
       return unless project
 
       Gitlab::AppLogger.info("Updating statistics for project #{project.id}")
 
-      project.statistics.refresh!(only: statistics.map(&:to_sym))
+      expire_repository_caches
+      expire_wiki_caches
+      project.statistics.refresh!(only: statistics)
     end
 
     private
 
+    def expire_repository_caches
+      if statistics.empty?
+        project.repository.expire_statistics_caches
+      elsif method_caches_to_expire.present?
+        project.repository.expire_method_caches(method_caches_to_expire)
+      end
+    end
+
+    def expire_wiki_caches
+      return unless project.wiki_enabled? && statistics.include?(:wiki_size)
+
+      project.wiki.repository.expire_method_caches([:size])
+    end
+
+    def method_caches_to_expire
+      strong_memoize(:method_caches_to_expire) do
+        statistics.map { |stat| STAT_TO_CACHED_METHOD[stat] }.compact
+      end
+    end
+
     def statistics
-      params[:statistics]
+      strong_memoize(:statistics) do
+        params[:statistics]&.map(&:to_sym)
+      end
     end
   end
 end

changelogs/unreleased/sh-flush-statistics-cache.yml

+---
+title: Flush statistics cache anytime it is updated
+merge_request: 52938
+author:
+type: fixed

spec/services/projects/update_statistics_service_spec.rb

@@ -3,6 +3,8 @@
 require 'spec_helper'
 
 RSpec.describe Projects::UpdateStatisticsService do
+  using RSpec::Parameterized::TableSyntax
+
   let(:service) { described_class.new(project, nil, statistics: statistics)}
   let(:statistics) { %w(repository_size) }
 
@@ -18,12 +20,46 @@ RSpec.describe Projects::UpdateStatisticsService do
     end
 
     context 'with an existing project' do
-      let(:project) { create(:project) }
+      let_it_be(:project) { create(:project) }
+
+      where(:statistics, :method_caches) do
+        []                                                   | %i(size commit_count)
+        ['repository_size']                                  | [:size]
+        [:repository_size]                                   | [:size]
+        [:lfs_objects_size]                                  | nil
+        [:commit_count]                                      | [:commit_count] # rubocop:disable Lint/BinaryOperatorWithIdenticalOperands
+        [:repository_size, :commit_count]                    | %i(size commit_count)
+        [:repository_size, :commit_count, :lfs_objects_size] | %i(size commit_count)
+      end
+
+      with_them do
+        it 'refreshes the project statistics' do
+          expect(project.statistics).to receive(:refresh!).with(only: statistics.map(&:to_sym)).and_call_original
+
+          service.execute
+        end
+
+        it 'invalidates the method caches after a refresh' do
+          expect(project.wiki.repository).not_to receive(:expire_method_caches)
+
+          if method_caches.present?
+            expect(project.repository).to receive(:expire_method_caches).with(method_caches).and_call_original
+          else
+            expect(project.repository).not_to receive(:expire_method_caches)
+          end
+
+          service.execute
+        end
+      end
+    end
+
+    context 'with an existing project with a Wiki' do
+      let(:project) { create(:project, :repository, :wiki_enabled) }
+      let(:statistics) { [:wiki_size] }
 
-      it 'refreshes the project statistics' do
-        expect_any_instance_of(ProjectStatistics).to receive(:refresh!)
-          .with(only: statistics.map(&:to_sym))
-          .and_call_original
+      it 'invalidates and refreshes Wiki size' do
+        expect(project.statistics).to receive(:refresh!).with(only: statistics).and_call_original
+        expect(project.wiki.repository).to receive(:expire_method_caches).with(%i(size)).and_call_original
 
         service.execute
       end