Override-the-caching-of-pages-that-have-comments--so-we-don-t-accidentally-serve-stale-pages-to-users-.patch

From 25c336594e2b215429aa2d75e88d35632377ad81 Mon Sep 17 00:00:00 2001
From: Myron Marston <myron.marston@gmail.com>
Date: Thu, 3 Dec 2009 13:21:49 -0800
Subject: [PATCH] Override the caching of pages that have comments, so we don't accidentally serve stale pages to users.

---
 config/environment.rb                 |    9 +++++++++
 lib/site_controller_etag_extension.rb |   18 ++++++++++++++++++
 2 files changed, 27 insertions(+), 0 deletions(-)
 create mode 100644 lib/site_controller_etag_extension.rb

diff --git a/config/environment.rb b/config/environment.rb
index 2b5cb16..d706e09 100644
--- a/config/environment.rb
+++ b/config/environment.rb
@@ -17,6 +17,8 @@ Radiant::Initializer.run do |config|
   # can be used as a placeholder for all extensions not explicitly named.
   # config.extensions = [ :all ]
 
+  config.load_paths << File.join(Rails.root, 'lib')
+
   # Your secret key for verifying cookie session data integrity.
   # If you change this key, all old sessions will become invalid!
   # Make sure the secret is at least 30 characters and all random,
@@ -76,6 +78,13 @@ Radiant::Initializer.run do |config|
     end
   end
 
+  # This is a bit of a hack, but I couldn't find any other way to make sure this module gets included
+  # once, and only once in dev mode.  Radiant seems to have different auto-loading / class-caching behavior
+  # compared to a standard Rails app.
+  config.to_prepare do
+    SiteController.send(:include, SiteControllerEtagExtension) unless SiteController.included_modules.include?(SiteControllerEtagExtension)
+  end
+
   config.gem 'will_paginate'
   config.gem 'fastercsv'
   config.gem 'sanitize'
diff --git a/lib/site_controller_etag_extension.rb b/lib/site_controller_etag_extension.rb
new file mode 100644
index 0000000..5604630
--- /dev/null
+++ b/lib/site_controller_etag_extension.rb
@@ -0,0 +1,18 @@
+module SiteControllerEtagExtension
+  def self.included(base)
+    base.alias_method_chain :set_cache_control, :etag
+  end
+
+  private
+
+  def set_cache_control_with_etag
+    if (request.head? || request.get?) && @page.cache? && @page.enable_comments?
+      expires_in nil, :private => true, "no-cache" => true
+
+      # Note: when a comment is added, :comment_count and :lock_version are updated.  :updated_at is not.
+      headers['ETag'] = Digest::MD5.hexdigest("#{@page.updated_at.to_s} : #{@page.lock_version.to_s}")
+    else
+      set_cache_control_without_etag
+    end
+  end
+end
\ No newline at end of file
-- 
1.6.5+GitX