Put Pages moves from namespace transfers in Sidekiq

This is the same as the previous commit, but when a namespace changes
its parent namespace via a transfer. (The previous commit is for a
namespace changing its own path directly.) We're moving Pages disk
operations from Puma to Sidekiq, and here that's behind the
`async_pages_move_namespace_transfer` feature flag.

app/models/concerns/storage/legacy_namespace.rb

@@ -23,7 +23,14 @@ module Storage
         former_parent_full_path = parent_was&.full_path
         parent_full_path = parent&.full_path
         Gitlab::UploadsTransfer.new.move_namespace(path, former_parent_full_path, parent_full_path)
-        Gitlab::PagesTransfer.new.move_namespace(path, former_parent_full_path, parent_full_path)
+
+        if ::Feature.enabled?(:async_pages_move_namespace_transfer, self)
+          run_after_commit do
+            Gitlab::PagesTransfer.new.async.move_namespace(path, former_parent_full_path, parent_full_path)
+          end
+        else
+          Gitlab::PagesTransfer.new.move_namespace(path, former_parent_full_path, parent_full_path)
+        end
       else
         Gitlab::UploadsTransfer.new.rename_namespace(full_path_before_last_save, full_path)
 

config/feature_flags/development/async_pages_move_namespace_transfer.yml

+---
+name: async_pages_move_namespace_transfer
+introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/40259
+rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/235808
+group: team::Scalability
+type: development
+default_enabled: false

spec/models/namespace_spec.rb

@@ -409,6 +409,8 @@ RSpec.describe Namespace do
 
         after do
           FileUtils.remove_entry(File.join(TestEnv.repos_path, parent.full_path), true)
+          FileUtils.remove_entry(File.join(TestEnv.repos_path, new_parent.full_path), true)
+          FileUtils.remove_entry(File.join(TestEnv.repos_path, child.full_path), true)
           FileUtils.remove_entry(File.join(uploads_dir, project.full_path), true)
           FileUtils.remove_entry(File.join(pages_dir, project.full_path), true)
         end
@@ -450,7 +452,17 @@ RSpec.describe Namespace do
         end
 
         context 'moving from one parent to another' do
-          it 'correctly moves the repository, uploads and pages' do
+          context 'when async_pages_move_namespace_transfer is disabled' do
+            it 'correctly moves the repository, uploads and pages' do
+              stub_feature_flags(async_pages_move_namespace_transfer: false)
+
+              child.update!(parent: new_parent)
+
+              expect_project_directories_at('new_parent/child')
+            end
+          end
+
+          it 'correctly moves the repository, uploads and pages', :sidekiq_inline do
             child.update!(parent: new_parent)
 
             expect_project_directories_at('new_parent/child')
@@ -458,7 +470,17 @@ RSpec.describe Namespace do
         end
 
         context 'moving from having a parent to root' do
-          it 'correctly moves the repository, uploads and pages' do
+          context 'when async_pages_move_namespace_transfer is disabled' do
+            it 'correctly moves the repository, uploads and pages' do
+              stub_feature_flags(async_pages_move_namespace_transfer: false)
+
+              child.update!(parent: nil)
+
+              expect_project_directories_at('child')
+            end
+          end
+
+          it 'correctly moves the repository, uploads and pages', :sidekiq_inline do
             child.update!(parent: nil)
 
             expect_project_directories_at('child')
@@ -466,7 +488,17 @@ RSpec.describe Namespace do
         end
 
         context 'moving from root to having a parent' do
-          it 'correctly moves the repository, uploads and pages' do
+          context 'when async_pages_move_namespace_transfer is disabled' do
+            it 'correctly moves the repository, uploads and pages' do
+              stub_feature_flags(async_pages_move_namespace_transfer: false)
+
+              parent.update!(parent: new_parent)
+
+              expect_project_directories_at('new_parent/parent/child')
+            end
+          end
+
+          it 'correctly moves the repository, uploads and pages', :sidekiq_inline do
             parent.update!(parent: new_parent)
 
             expect_project_directories_at('new_parent/parent/child')