From df1653174be233f2737d8ec281325dee54011947 Mon Sep 17 00:00:00 2001
From: Eugen Rochko <eugen@zeonfederated.com>
Date: Thu, 19 Nov 2020 17:38:06 +0100
Subject: [PATCH] Add cache buster feature for media files (#15155)

Nginx can be configured to bypass proxy cache when a special header
is in the request. If the response is cacheable, it will replace
the cache for that request. Proxy caching of media files is
desirable when using object storage as a way of minimizing bandwidth
costs, but has the drawback of leaving deleted media files for
a configured amount of cache time. A cache buster can make those
media files immediately unavailable. This especially makes sense
when suspending and unsuspending an account.
---
 app/lib/cache_buster.rb                   | 28 +++++++++++++++++++++++
 app/services/suspend_account_service.rb   |  2 ++
 app/services/unsuspend_account_service.rb |  2 ++
 app/workers/cache_buster_worker.rb        | 18 +++++++++++++++
 config/initializers/cache_buster.rb       | 10 ++++++++
 config/initializers/paperclip.rb          |  1 -
 6 files changed, 60 insertions(+), 1 deletion(-)
 create mode 100644 app/lib/cache_buster.rb
 create mode 100644 app/workers/cache_buster_worker.rb
 create mode 100644 config/initializers/cache_buster.rb

diff --git a/app/lib/cache_buster.rb b/app/lib/cache_buster.rb
new file mode 100644
index 000000000..035611518
--- /dev/null
+++ b/app/lib/cache_buster.rb
@@ -0,0 +1,28 @@
+# frozen_string_literal: true
+
+class CacheBuster
+  def initialize(options = {})
+    @secret_header = options[:secret_header] || 'Secret-Header'
+    @secret        = options[:secret] || 'True'
+  end
+
+  def bust(url)
+    site = Addressable::URI.parse(url).normalized_site
+
+    request_pool.with(site) do |http_client|
+      build_request(url, http_client).perform
+    end
+  end
+
+  private
+
+  def request_pool
+    RequestPool.current
+  end
+
+  def build_request(url, http_client)
+    Request.new(:get, url, http_client: http_client).tap do |request|
+      request.add_headers(@secret_header => @secret)
+    end
+  end
+end
diff --git a/app/services/suspend_account_service.rb b/app/services/suspend_account_service.rb
index 7c70a6021..19d65280d 100644
--- a/app/services/suspend_account_service.rb
+++ b/app/services/suspend_account_service.rb
@@ -78,6 +78,8 @@ class SuspendAccountService < BaseService
               Rails.logger.warn "Tried to change permission on non-existent file #{attachment.path(style)}"
             end
           end
+
+          CacheBusterWorker.perform_async(attachment.path(style)) if Rails.configuration.x.cache_buster_enabled
         end
       end
     end
diff --git a/app/services/unsuspend_account_service.rb b/app/services/unsuspend_account_service.rb
index a81d1ac4f..f07a3f053 100644
--- a/app/services/unsuspend_account_service.rb
+++ b/app/services/unsuspend_account_service.rb
@@ -69,6 +69,8 @@ class UnsuspendAccountService < BaseService
               Rails.logger.warn "Tried to change permission on non-existent file #{attachment.path(style)}"
             end
           end
+
+          CacheBusterWorker.perform_async(attachment.path(style)) if Rails.configuration.x.cache_buster_enabled
         end
       end
     end
diff --git a/app/workers/cache_buster_worker.rb b/app/workers/cache_buster_worker.rb
new file mode 100644
index 000000000..5ad0a44cb
--- /dev/null
+++ b/app/workers/cache_buster_worker.rb
@@ -0,0 +1,18 @@
+# frozen_string_literal: true
+
+class CacheBusterWorker
+  include Sidekiq::Worker
+  include RoutingHelper
+
+  sidekiq_options queue: 'pull'
+
+  def perform(path)
+    cache_buster.bust(full_asset_url(path))
+  end
+
+  private
+
+  def cache_buster
+    CacheBuster.new(Rails.configuration.x.cache_buster)
+  end
+end
diff --git a/config/initializers/cache_buster.rb b/config/initializers/cache_buster.rb
new file mode 100644
index 000000000..227e450f3
--- /dev/null
+++ b/config/initializers/cache_buster.rb
@@ -0,0 +1,10 @@
+# frozen_string_literal: true
+
+Rails.application.configure do
+  config.x.cache_buster_enabled = ENV['CACHE_BUSTER_ENABLED'] == 'true'
+
+  config.x.cache_buster = {
+    secret_header: ENV['CACHE_BUSTER_SECRET_HEADER'],
+    secret: ENV['CACHE_BUSTER_SECRET'],
+  }
+end
diff --git a/config/initializers/paperclip.rb b/config/initializers/paperclip.rb
index b841d5220..25adcd8d6 100644
--- a/config/initializers/paperclip.rb
+++ b/config/initializers/paperclip.rb
@@ -107,7 +107,6 @@ elsif ENV['SWIFT_ENABLED'] == 'true'
 else
   Paperclip::Attachment.default_options.merge!(
     storage: :filesystem,
-    use_timestamp: true,
     path: File.join(ENV.fetch('PAPERCLIP_ROOT_PATH', File.join(':rails_root', 'public', 'system')), ':prefix_path:class', ':attachment', ':id_partition', ':style', ':filename'),
     url: ENV.fetch('PAPERCLIP_ROOT_URL', '/system') + '/:prefix_url:class/:attachment/:id_partition/:style/:filename',
   )