Update project_daily_statistics synchronally

The ProjectDailyStatisticsWorker queue accumulates jobs
from time to time, considering how often the git_upload_pack
endpoint is called (taking up to 7 minutes to take the job
from the queue in a few cases).

Turns out that even though this is a low-priority queue (and
it's OK to take a bit more time to process it) it was
seen that the work it does takes around 1.8s (99th percentile),
and 0.8s (99th percentile) DB time, which doesn't explain
involving Sidekiq (and Redis) in the work pipeline.

Here we move the processing out of Sidekiq and back to the
web request behind a feature flag (and deprecate the worker).

app/controllers/repositories/git_http_controller.rb

@@ -23,7 +23,7 @@ module Repositories
 
     # POST /foo/bar.git/git-upload-pack (git pull)
     def git_upload_pack
-      enqueue_fetch_statistics_update
+      update_fetch_statistics
 
       render_ok
     end
@@ -76,12 +76,16 @@ module Repositories
       render plain: exception.message, status: :service_unavailable
     end
 
-    def enqueue_fetch_statistics_update
+    def update_fetch_statistics
+      return unless project
       return if Gitlab::Database.read_only?
       return unless repo_type.project?
-      return unless project&.daily_statistics_enabled?
 
-      ProjectDailyStatisticsWorker.perform_async(project.id) # rubocop:disable CodeReuse/Worker
+      if Feature.enabled?(:project_statistics_sync, project, default_enabled: true)
+        Projects::FetchStatisticsIncrementService.new(project).execute
+      else
+        ProjectDailyStatisticsWorker.perform_async(project.id) # rubocop:disable CodeReuse/Worker
+      end
     end
 
     def access

app/models/project.rb

@@ -774,10 +774,6 @@ class Project < ApplicationRecord
     { scope: :project, status: auto_devops&.enabled || Feature.enabled?(:force_autodevops_on_by_default, self) }
   end
 
-  def daily_statistics_enabled?
-    Feature.enabled?(:project_daily_statistics, self, default_enabled: true)
-  end
-
   def unlink_forks_upon_visibility_decrease_enabled?
     Feature.enabled?(:unlink_fork_network_upon_visibility_decrease, self, default_enabled: true)
   end

app/workers/project_daily_statistics_worker.rb

 # frozen_string_literal: true
 
+# Deprecated: https://gitlab.com/gitlab-org/gitlab/-/issues/214585
 class ProjectDailyStatisticsWorker # rubocop:disable Scalability/IdempotentWorker
   include ApplicationWorker
 

lib/api/project_statistics.rb

@@ -4,7 +4,6 @@ module API
   class ProjectStatistics < Grape::API
     before do
       authenticate!
-      not_found! unless user_project.daily_statistics_enabled?
       authorize! :daily_statistics, user_project
     end
 

spec/controllers/repositories/git_http_controller_spec.rb

@@ -95,7 +95,7 @@ describe Repositories::GitHttpController do
         allow(controller).to receive(:access_check).and_return(nil)
       end
 
-      after do
+      def send_request
         post :git_upload_pack, params: params
       end
 
@@ -106,16 +106,46 @@ describe Repositories::GitHttpController do
 
         it 'does not update project statistics' do
           expect(ProjectDailyStatisticsWorker).not_to receive(:perform_async)
+
+          send_request
         end
       end
 
       if expected
-        it 'updates project statistics' do
-          expect(ProjectDailyStatisticsWorker).to receive(:perform_async)
+        context 'when project_statistics_sync feature flag is disabled' do
+          before do
+            stub_feature_flags(project_statistics_sync: false)
+          end
+
+          it 'updates project statistics async' do
+            expect(ProjectDailyStatisticsWorker).to receive(:perform_async)
+
+            send_request
+          end
+        end
+
+        it 'updates project statistics sync' do
+          expect { send_request }.to change {
+            Projects::DailyStatisticsFinder.new(project).total_fetch_count
+          }.from(0).to(1)
         end
       else
+        context 'when project_statistics_sync feature flag is disabled' do
+          before do
+            stub_feature_flags(project_statistics_sync: false)
+          end
+
+          it 'does not update project statistics' do
+            expect(ProjectDailyStatisticsWorker).not_to receive(:perform_async)
+
+            send_request
+          end
+        end
+
         it 'does not update project statistics' do
-          expect(ProjectDailyStatisticsWorker).not_to receive(:perform_async)
+          expect { send_request }.not_to change {
+            Projects::DailyStatisticsFinder.new(project).total_fetch_count
+          }.from(0)
         end
       end
     end

spec/models/project_spec.rb

@@ -2645,18 +2645,6 @@ describe Project do
     end
   end
 
-  describe '#daily_statistics_enabled?' do
-    it { is_expected.to be_daily_statistics_enabled }
-
-    context 'when :project_daily_statistics is disabled for the project' do
-      before do
-        stub_feature_flags(project_daily_statistics: { thing: subject, enabled: false })
-      end
-
-      it { is_expected.not_to be_daily_statistics_enabled }
-    end
-  end
-
   describe '#change_head' do
     let(:project) { create(:project, :repository) }
 

spec/requests/api/project_statistics_spec.rb

@@ -50,13 +50,5 @@ describe API::ProjectStatistics do
       expect(response).to have_gitlab_http_status(:forbidden)
       expect(json_response['message']).to eq('403 Forbidden')
     end
-
-    it 'responds with 404 when daily_statistics_enabled? is false' do
-      stub_feature_flags(project_daily_statistics: { thing: public_project, enabled: false })
-
-      get api("/projects/#{public_project.id}/statistics", maintainer)
-
-      expect(response).to have_gitlab_http_status(:not_found)
-    end
   end
 end