Adds Rollback functionality to HashedStorage migration

We are adding sidekiq workers and service classes to allow to rollback
a hashed storage migration. There are some refactoring involved as well
as part of the code can be reused by both the migration and the rollback
logic.

6 files changed, 195 insertions, 0 deletions

diff --git a/app/models/project.rb b/app/models/project.rb
index 47baf899222..400e86123f7 100644
--- a/app/models/project.rb
+++ b/app/models/project.rb
@@ -1976,6 +1976,16 @@ class Project < ActiveRecord::Base
     end
   end
 
+  def rollback_to_legacy_storage!
+    return if legacy_storage?
+
+    if git_transfer_in_progress?
+      ProjectRollbackHashedStorageWorker.perform_in(Gitlab::ReferenceCounter::REFERENCE_EXPIRE_TIME, id)
+    else
+      ProjectRollbackHashedStorageWorker.perform_async(id)
+    end
+  end
+
   def git_transfer_in_progress?
     repo_reference_count > 0 || wiki_reference_count > 0
   end
diff --git a/app/services/projects/hashed_storage/rollback_attachments_service.rb b/app/services/projects/hashed_storage/rollback_attachments_service.rb
new file mode 100644
index 00000000000..5183609ab85
--- /dev/null
+++ b/app/services/projects/hashed_storage/rollback_attachments_service.rb
@@ -0,0 +1,53 @@
+# frozen_string_literal: true
+
+module Projects
+  module HashedStorage
+    AttachmentRollbackError = Class.new(StandardError)
+
+    class RollbackAttachmentsService < BaseService
+      attr_reader :logger, :old_disk_path
+
+      def initialize(project, logger: nil)
+        @project = project
+        @logger = logger || Rails.logger
+      end
+
+      def execute
+        origin = FileUploader.absolute_base_dir(project)
+        project.storage_version = ::Project::HASHED_STORAGE_FEATURES[:repository]
+        target = FileUploader.absolute_base_dir(project)
+
+        result = move_folder!(origin, target)
+        project.save!
+
+        if result && block_given?
+          yield
+        end
+
+        result
+      end
+
+      private
+
+      def move_folder!(old_path, new_path)
+        unless File.directory?(old_path)
+          logger.info("Skipped attachments rollback from '#{old_path}' to '#{new_path}', source path doesn't exist or is not a directory (PROJECT_ID=#{project.id})")
+          return true
+        end
+
+        if File.exist?(new_path)
+          logger.error("Cannot rollback attachments from '#{old_path}' to '#{new_path}', target path already exist (PROJECT_ID=#{project.id})")
+          raise AttachmentRollbackError, "Target path '#{new_path}' already exist"
+        end
+
+        # Create hashed storage base path folder
+        FileUtils.mkdir_p(File.dirname(new_path))
+
+        FileUtils.mv(old_path, new_path)
+        logger.info("Rolledback project attachments from '#{old_path}' to '#{new_path}' (PROJECT_ID=#{project.id})")
+
+        true
+      end
+    end
+  end
+end
diff --git a/app/services/projects/hashed_storage/rollback_repository_service.rb b/app/services/projects/hashed_storage/rollback_repository_service.rb
new file mode 100644
index 00000000000..b57d05c50ca
--- /dev/null
+++ b/app/services/projects/hashed_storage/rollback_repository_service.rb
@@ -0,0 +1,52 @@
+# frozen_string_literal: true
+
+module Projects
+  module HashedStorage
+    class RollbackRepositoryService < BaseRepositoryService
+      def execute
+        try_to_set_repository_read_only!
+
+        @old_storage_version = project.storage_version
+        project.storage_version = nil
+        project.ensure_storage_path_exists
+
+        @new_disk_path = project.disk_path
+
+        result = move_repository(old_disk_path, new_disk_path)
+
+        if move_wiki
+          result &&= move_repository("#{old_wiki_disk_path}", "#{new_disk_path}.wiki")
+        end
+
+        if result
+          project.write_repository_config
+          project.track_project_repository
+        else
+          rollback_folder_move
+          project.storage_version = ::Project::HASHED_STORAGE_FEATURES[:repository]
+        end
+
+        project.repository_read_only = false
+        project.save!
+
+        if result && block_given?
+          yield
+        end
+
+        result
+      end
+
+      private
+
+      def try_to_set_repository_read_only!
+        # Mitigate any push operation to start during migration
+        unless project.set_repository_read_only!
+          migration_error = "Target repository '#{old_disk_path}' cannot be made read-only as there is a git transfer in progress"
+          logger.error migration_error
+
+          raise RepositoryRollbackError, migration_error
+        end
+      end
+    end
+  end
+end
diff --git a/app/services/projects/hashed_storage/rollback_service.rb b/app/services/projects/hashed_storage/rollback_service.rb
new file mode 100644
index 00000000000..25767f5de5e
--- /dev/null
+++ b/app/services/projects/hashed_storage/rollback_service.rb
@@ -0,0 +1,37 @@
+# frozen_string_literal: true
+
+module Projects
+  module HashedStorage
+    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 || Rails.logger
+      end
+
+      def execute
+        # Rollback attachments from Hashed Storage to Legacy
+        if project.hashed_storage?(:attachments)
+          return false unless rollback_attachments
+        end
+
+        # Rollback repository from Hashed Storage to Legacy
+        if project.hashed_storage?(:repository)
+          rollback_repository
+        end
+      end
+
+      private
+
+      def rollback_attachments
+        HashedStorage::RollbackAttachmentsService.new(project, logger: logger).execute
+      end
+
+      def rollback_repository
+        HashedStorage::RollbackRepositoryService.new(project, old_disk_path, logger: logger).execute
+      end
+    end
+  end
+end
diff --git a/app/workers/all_queues.yml b/app/workers/all_queues.yml
index 337f39b2091..82351c1334f 100644
--- a/app/workers/all_queues.yml
+++ b/app/workers/all_queues.yml
@@ -127,6 +127,7 @@
 - project_destroy
 - project_export
 - project_migrate_hashed_storage
+- project_rollback_hashed_storage
 - project_service
 - propagate_service_template
 - reactive_caching
diff --git a/app/workers/project_rollback_hashed_storage_worker.rb b/app/workers/project_rollback_hashed_storage_worker.rb
new file mode 100644
index 00000000000..38faffd2bfa
--- /dev/null
+++ b/app/workers/project_rollback_hashed_storage_worker.rb
@@ -0,0 +1,42 @@
+# frozen_string_literal: true
+
+class ProjectRollbackHashedStorageWorker
+  include ApplicationWorker
+
+  LEASE_TIMEOUT = 30.seconds.to_i
+
+  # rubocop: disable CodeReuse/ActiveRecord
+  def perform(project_id, old_disk_path = nil)
+    uuid = lease_for(project_id).try_obtain
+
+    if uuid
+      project = Project.find_by(id: project_id)
+      return if project.nil? || project.pending_delete?
+
+      old_disk_path ||= project.disk_path
+
+      ::Projects::HashedStorage::RollbackService.new(project, old_disk_path, logger: logger).execute
+    else
+      return false
+    end
+
+  ensure
+    cancel_lease_for(project_id, uuid) if uuid
+  end
+  # rubocop: enable CodeReuse/ActiveRecord
+
+  def lease_for(project_id)
+    Gitlab::ExclusiveLease.new(lease_key(project_id), timeout: LEASE_TIMEOUT)
+  end
+
+  private
+
+  def lease_key(project_id)
+    # we share the same lease key for both migration and rollback so they don't run simultaneously
+    "#{ProjectMigrateHashedStorageWorker::LEASE_KEY_SEGMENT}:#{project_id}"
+  end
+
+  def cancel_lease_for(project_id, uuid)
+    Gitlab::ExclusiveLease.cancel(lease_key(project_id), uuid)
+  end
+end