Fix storage rollback regression caused by previous refactor

Regression was caused by the removal of custom initializer.

It wasn't caught during MR review nor by automated tests because of
poor test coverage.

This adds integration examples for both rollback situations and improves
on logging.

app/services/projects/hashed_storage/base_repository_service.rb

@@ -40,7 +40,13 @@ module Projects
           return true
         end
 
-        gitlab_shell.mv_repository(project.repository_storage, from_name, to_name)
+        gitlab_shell.mv_repository(project.repository_storage, from_name, to_name).tap do |moved|
+          if moved
+            logger.info("Repository moved from '#{from_name}' to '#{to_name}' (PROJECT_ID=#{project.id})")
+          else
+            logger.error("Repository cannot be moved from '#{from_name}' to '#{to_name}' (PROJECT_ID=#{project.id})")
+          end
+        end
       end
 
       def move_repositories

app/services/projects/hashed_storage/rollback_service.rb

@@ -5,6 +5,12 @@ module Projects
     class RollbackService < BaseService
       attr_reader :logger, :old_disk_path
 
+      def initialize(project, old_disk_path, logger: nil)
+        @project = project
+        @old_disk_path = old_disk_path
+        @logger = logger || Gitlab::AppLogger
+      end
+
       def execute
         # Rollback attachments from Hashed Storage to Legacy
         if project.hashed_storage?(:attachments)

changelogs/unreleased/211452-rollback_to_legacy-causes-repos-to-404.yml

+---
+title: Fix storage rollback regression caused by previous refactor
+merge_request: 28496
+author:
+type: fixed

spec/services/projects/hashed_storage/rollback_service_spec.rb

@@ -5,6 +5,11 @@ require 'spec_helper'
 describe Projects::HashedStorage::RollbackService do
   let(:project) { create(:project, :empty_repo, :wiki_repo) }
   let(:logger) { double }
+  let!(:project_attachment) { build(:file_uploader, project: project) }
+  let(:project_hashed_path) { Storage::Hashed.new(project).disk_path }
+  let(:project_legacy_path) { Storage::LegacyProject.new(project).disk_path }
+  let(:wiki_hashed_path) { "#{project_hashed_path}.wiki" }
+  let(:wiki_legacy_path) { "#{project_legacy_path}.wiki" }
 
   subject(:service) { described_class.new(project, project.disk_path, logger: logger) }
 
@@ -26,6 +31,20 @@ describe Projects::HashedStorage::RollbackService do
 
         service.execute
       end
+
+      it 'rollbacks to legacy storage' do
+        hashed_attachments_path = FileUploader.absolute_base_dir(project)
+        legacy_project = project.dup
+        legacy_project.storage_version = nil
+        legacy_attachments_path = FileUploader.absolute_base_dir(legacy_project)
+
+        expect(logger).to receive(:info).with(/Project attachments moved from '#{hashed_attachments_path}' to '#{legacy_attachments_path}'/)
+
+        expect(logger).to receive(:info).with(/Repository moved from '#{project_hashed_path}' to '#{project_legacy_path}'/)
+        expect(logger).to receive(:info).with(/Repository moved from '#{wiki_hashed_path}' to '#{wiki_legacy_path}'/)
+
+        expect { service.execute }.to change { project.storage_version }.from(2).to(nil)
+      end
     end
 
     context 'repository rollback' do
@@ -47,6 +66,13 @@ describe Projects::HashedStorage::RollbackService do
 
         service.execute
       end
+
+      it 'rollbacks to legacy storage' do
+        expect(logger).to receive(:info).with(/Repository moved from '#{project_hashed_path}' to '#{project_legacy_path}'/)
+        expect(logger).to receive(:info).with(/Repository moved from '#{wiki_hashed_path}' to '#{wiki_legacy_path}'/)
+
+        expect { service.execute }.to change { project.storage_version }.from(1).to(nil)
+      end
     end
   end
 end