From df990afadca43bcead8b1c31f12a0471caa15ae7 Mon Sep 17 00:00:00 2001
From: Vaidehi Joshi <vaidehi.sj@gmail.com>
Date: Wed, 5 Aug 2020 12:34:12 -0700
Subject: [PATCH] Conditionally remove `no-cache` from Fastly headers (#9631)
 [deploy]

* Rename FastlyHeaders to CachingHeaders, conditionally experiment with removing no-cache

We suspect that it is safe to remove `no-cache` entirely from the Cache-Control headers that are sent
along to Fastly, but there is no great way to confirm this hypothesis. We're testing this by experimenting
on one single article. We will conditionally default to the same headers that we send to Nginx, and send
those headers to Fastly (by removing `no-cache` and adding in `max-age`, which should be ignored since Fastly
also has Surrogate-Control headers added to it, which include a `max-age`, which Fastly should prioritize
over any other `max-age`.

Once we've confirmed that this doesn't cause issues on the Fastly side, we can remove this check and use
the same Cache-Control headers for both Fastly and Nginx.

* Add check for request.env[REQUEST_PATH].present?
---
 app/controllers/application_controller.rb        |  2 +-
 .../{fastly_headers.rb => caching_headers.rb}    | 16 +++++++++++++---
 2 files changed, 14 insertions(+), 4 deletions(-)
 rename app/controllers/concerns/{fastly_headers.rb => caching_headers.rb} (74%)

diff --git a/app/controllers/application_controller.rb b/app/controllers/application_controller.rb
index af9863b7b..d2d6f66da 100644
--- a/app/controllers/application_controller.rb
+++ b/app/controllers/application_controller.rb
@@ -6,7 +6,7 @@ class ApplicationController < ActionController::Base
   include SessionCurrentUser
   include ValidRequest
   include Pundit
-  include FastlyHeaders
+  include CachingHeaders
   include ImageUploads
   include VerifySetupCompleted
 
diff --git a/app/controllers/concerns/fastly_headers.rb b/app/controllers/concerns/caching_headers.rb
similarity index 74%
rename from app/controllers/concerns/fastly_headers.rb
rename to app/controllers/concerns/caching_headers.rb
index 1100f1e3a..bf0c1db49 100644
--- a/app/controllers/concerns/fastly_headers.rb
+++ b/app/controllers/concerns/caching_headers.rb
@@ -1,4 +1,4 @@
-module FastlyHeaders
+module CachingHeaders
   extend ActiveSupport::Concern
 
   # The following is from the now deprecated fastly-rails gem
@@ -12,11 +12,21 @@ module FastlyHeaders
   # custom config example:
   #  {cache_control: 'public, no-cache, maxage=xyz', surrogate_control: 'max-age: 100'}
   def set_cache_control_headers(
-    max_age = 1.day.to_i, cache_control: "public, no-cache",
+    max_age = 1.day.to_i,
     surrogate_control: nil, stale_while_revalidate: nil, stale_if_error: 26_400
   )
-    request.session_options[:skip] = true # no cookies
 
+    # TODO: [@forem/delightful]: Once we've tested that removing `no-cache` from the Cache-Control headers
+    # does not adversely affect fastly, we should remove this specific check entirely.
+    article_requested = request.env["REQUEST_PATH"].present? &&
+      request.env["REQUEST_PATH"].include?("the-3-biggest-misconceptions-about-diversity-3hkm")
+    cache_control = if article_requested
+                      "public, max-age=86400"
+                    else
+                      "public, no-cache"
+                    end
+
+    request.session_options[:skip] = true # no cookies
     response.headers["Cache-Control"] = cache_control
 
     response.headers["Surrogate-Control"] = surrogate_control.presence || build_surrogate_control(