Add cache buster feature for media files (mastodon#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.
hachyderm · Nov 19, 2020 · df16531 · df16531
1 parent 1242e57
commit df16531
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Showing 6 changed files with 60 additions and 1 deletion.
diff --git a/app/lib/cache_buster.rb 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
@@ -78,6 +78,8 @@ def privatize_media_attachments!
               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
@@ -69,6 +69,8 @@ def publish_media_attachments!
               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
@@ -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
@@ -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
@@ -107,7 +107,6 @@
 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',
   )
-Original file line number
+Diff line change
@@ Expand Up / @@ -78,6 +78,8 @@ def privatize_media_attachments! @@
                   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
@@ Expand Down @@