Make dir app/models/fluentd/setting_archive/

and move backup_file model under it. prepare for gathering models that concernig about archive

app/controllers/fluentd/settings/histories_controller.rb

@@ -5,7 +5,7 @@ class Fluentd::Settings::HistoriesController < ApplicationController
 
   def index
     @backup_files = @fluentd.agent.backup_files_in_new_order.map do |file_path|
-      Fluentd::Setting::BackupFile.new(file_path)
+      Fluentd::SettingArchive::BackupFile.new(file_path)
     end
   end
 
@@ -21,6 +21,6 @@ class Fluentd::Settings::HistoriesController < ApplicationController
 
   def find_backup_file
     #Do not use BackupFile.new(params[:id]) because params[:id] can be any path.
-    @backup_file = Fluentd::Setting::BackupFile.find_by_file_id(@fluentd.agent.config_backup_dir, params[:id])
+    @backup_file = Fluentd::SettingArchive::BackupFile.find_by_file_id(@fluentd.agent.config_backup_dir, params[:id])
   end
 end

app/controllers/fluentd/settings/running_backup_controller.rb

@@ -14,6 +14,6 @@ class Fluentd::Settings::RunningBackupController < ApplicationController
   private
 
   def find_backup_file
-    @backup_file = Fluentd::Setting::BackupFile.new(@fluentd.agent.running_config_backup_file)
+    @backup_file = Fluentd::SettingArchive::BackupFile.new(@fluentd.agent.running_config_backup_file)
   end
 end

app/controllers/fluentd/settings_controller.rb

@@ -7,10 +7,10 @@ class Fluentd::SettingsController < ApplicationController
 
   def show
     @backup_files = @fluentd.agent.backup_files_in_new_order.first(Settings.histories_count_in_preview).map do |file_path|
-      Fluentd::Setting::BackupFile.new(file_path)
+      Fluentd::SettingArchive::BackupFile.new(file_path)
     end
 
-    @running_backedup_file = Fluentd::Setting::BackupFile.new(@fluentd.agent.running_config_backup_file)
+    @running_backedup_file = Fluentd::SettingArchive::BackupFile.new(@fluentd.agent.running_config_backup_file)
   end
 
   def edit

app/models/fluentd/setting_archive/backup_file.rb

@@ -1,5 +1,5 @@
 class Fluentd
-  module Setting
+  module SettingArchive
     class BackupFile
       attr_accessor :file_path
 

spec/features/fluentd/setting/hisotries_spec.rb

@@ -26,7 +26,7 @@ describe "histories", stub: :daemon do
   end
 
   describe 'show' do
-    let(:last_backup_file) { Fluentd::Setting::BackupFile.new(daemon.agent.backup_files_in_new_order.first) }
+    let(:last_backup_file) { Fluentd::SettingArchive::BackupFile.new(daemon.agent.backup_files_in_new_order.first) }
 
     before do
       visit "/daemon/setting/histories/#{last_backup_file.file_id}"