--- a/config/environments/development.rb	Tue Mar 01 16:34:29 2016 +0900
+++ b/config/environments/development.rb	Fri May 13 04:32:21 2016 +0900
@@ -9,16 +9,43 @@
   # Do not eager load code on boot.
   config.eager_load = false
 
-  # Show full error reports and disable caching.
-  config.consider_all_requests_local       = true
-  config.action_controller.perform_caching = false
+  # Show full error reports.
+  config.consider_all_requests_local = true
+
+  # Enable/disable caching. By default caching is disabled.
+  if Rails.root.join("tmp/caching-dev.txt").exist?
+    config.action_controller.perform_caching = true
+
+    # config.cache_store = :memory_store
+    config.public_file_server.headers = {
+      "Cache-Control" => "public, max-age=172800"
+    }
+  else
+    config.action_controller.perform_caching = false
+
+    # config.cache_store = :null_store
+  end
 
   # Don't care if the mailer can't send.
   # config.action_mailer.raise_delivery_errors = false
 
+  # config.action_mailer.perform_caching = false
+
   # Print deprecation notices to the Rails logger.
   config.active_support.deprecation = :log
 
+  # Raise an error on page load if there are pending migrations.
+  # config.active_record.migration_error = :page_load
+
+  # Debug mode disables concatenation and preprocessing of assets.
+  # This option may cause significant delays in view rendering with a large
+  # number of complex assets.
+  # config.assets.debug = true
+
   # Raises error for missing translations
   # config.action_view.raise_on_missing_translations = true
+
+  # Use an evented file watcher to asynchronously detect changes in source code,
+  # routes, locales, etc. This feature depends on the listen gem.
+  # config.file_watcher = ActiveSupport::EventedFileUpdateChecker
 end