config.action_dispatch.rack_cache should set explicitly to enable Rack::Cache

actionpack/lib/action_dispatch/railtie.rb

@@ -12,12 +12,7 @@ module ActionDispatch
     config.action_dispatch.rescue_templates = { }
     config.action_dispatch.rescue_responses = { }
     config.action_dispatch.default_charset = nil
-
-    config.action_dispatch.rack_cache = {
-      :metastore => "rails:/",
-      :entitystore => "rails:/",
-      :verbose => false
-    }
+    config.action_dispatch.rack_cache = false
 
     config.action_dispatch.default_headers = {
       'X-Frame-Options' => 'SAMEORIGIN',

railties/lib/rails/application.rb

@@ -297,6 +297,15 @@ module Rails
             error.message << ' Be sure to add rack-cache to your Gemfile'
             raise
           end
+
+          if rack_cache == true
+            rack_cache = {
+              :metastore => "rails:/",
+              :entitystore => "rails:/",
+              :verbose => false
+            }
+          end
+
           require "action_dispatch/http/rack_cache"
           middleware.use ::Rack::Cache, rack_cache
         end

railties/lib/rails/generators/rails/app/templates/config/environments/production.rb.tt

@@ -14,6 +14,11 @@
   config.consider_all_requests_local       = false
   config.action_controller.perform_caching = true
 
+  # Enable Rack::Cache to put a simple HTTP cache in front of your application
+  # Add `rack-cache` to your Gemfile before enabling this.
+  # For large-scale production use, consider using a caching reverse proxy like nginx, varnish or squid.
+  # config.action_dispatch.rack_cache = true
+
   # Disable Rails's static asset server (Apache or nginx will already do this).
   config.serve_static_assets = false
 

railties/test/application/middleware_test.rb

@@ -56,11 +56,20 @@ module ApplicationTests
       assert !middleware.include?("Rack::Sendfile"), "Rack::Sendfile is not included in the default stack unless you set config.action_dispatch.x_sendfile_header"
     end
 
-    test "Rack::Cache is present when action_controller.perform_caching is set" do
+    test "Rack::Cache is not included by default" do
       add_to_config "config.action_controller.perform_caching = true"
 
       boot!
 
+      assert !middleware.include?("Rack::Cache"), "Rack::Cache is not included in the default stack unless you set config.action_dispatch.rack_cache"
+    end
+
+    test "Rack::Cache is present when action_controller.perform_caching is set and action_dispatch.rack_cache is set" do
+      add_to_config "config.action_controller.perform_caching = true"
+      add_to_config "config.action_dispatch.rack_cache = true"
+
+      boot!
+
       assert_equal "Rack::Cache", middleware.first
     end