Add support for more HTTP cache controls

From <https://tools.ietf.org/html/rfc5861>:

> The stale-if-error HTTP Cache-Control extension allows a cache to
> return a stale response when an error -- e.g., a 500 Internal Server
> Error, a network segment, or DNS failure -- is encountered, rather
> than returning a "hard" error.  This improves availability.
>
> The stale-while-revalidate HTTP Cache-Control extension allows a
> cache to immediately return a stale response while it revalidates it
> in the background, thereby hiding latency (both in the network and on
> the server) from clients.

These are useful, fully standardized parts of the HTTP protocol with
widespread support among CDN vendors. Supporting them will make it
easier to utilize reverse proxies and CDNs from Rails.

1 files changed, 3 insertions, 1 deletions

diff --git a/actionpack/lib/action_controller/metal/conditional_get.rb b/actionpack/lib/action_controller/metal/conditional_get.rb
index 06b6a95ff8..4be4557e2c 100644
--- a/actionpack/lib/action_controller/metal/conditional_get.rb
+++ b/actionpack/lib/action_controller/metal/conditional_get.rb
@@ -235,7 +235,9 @@ module ActionController
       response.cache_control.merge!(
         max_age: seconds,
         public: options.delete(:public),
-        must_revalidate: options.delete(:must_revalidate)
+        must_revalidate: options.delete(:must_revalidate),
+        stale_while_revalidate: options.delete(:stale_while_revalidate),
+        stale_if_error: options.delete(:stale_if_error),
       )
       options.delete(:private)