PERF: Cache ToS and Privacy Policy paths (discourse#21860)

Checking if the topic exists happened often and that can cause
performance issues.

app/serializers/post_action_type_serializer.rb

@@ -18,11 +18,11 @@ def name
   end
 
   def description
-    i18n("description", tos_url: tos_path, base_path: Discourse.base_path)
+    i18n("description", tos_url: tos_url, base_path: Discourse.base_path)
   end
 
   def short_description
-    i18n("short_description", tos_url: tos_path, base_path: Discourse.base_path)
+    i18n("short_description", tos_url: tos_url, base_path: Discourse.base_path)
   end
 
   def name_key

app/serializers/site_serializer.rb

@@ -288,23 +288,15 @@ def include_denied_emojis?
   end
 
   def tos_url
-    if SiteSetting.tos_url.present?
-      SiteSetting.tos_url
-    elsif SiteSetting.tos_topic_id > 0 && Topic.exists?(id: SiteSetting.tos_topic_id)
-      "#{Discourse.base_path}/tos"
-    end
+    Discourse.tos_url
   end
 
   def include_tos_url?
     tos_url.present?
   end
 
   def privacy_policy_url
-    if SiteSetting.privacy_policy_url.present?
-      SiteSetting.privacy_policy_url
-    elsif SiteSetting.privacy_topic_id > 0 && Topic.exists?(id: SiteSetting.privacy_topic_id)
-      "#{Discourse.base_path}/privacy"
-    end
+    Discourse.privacy_policy_url
   end
 
   def include_privacy_policy_url?

app/views/layouts/_noscript_footer.html.erb

@@ -16,17 +16,17 @@
           <a href='<%= path "/guidelines" %>' itemprop="url"><%= t 'guidelines_topic.title' %> </a>
         </span>
       </li>
-      <% if path = tos_path.presence %>
+      <% if tos_url.present? %>
         <li itemscope itemtype='http://schema.org/SiteNavigationElement'>
           <span itemprop='name'>
-            <a href='<%= path %>' itemprop="url"><%= t 'tos_topic.title' %> </a>
+            <a href='<%= tos_url %>' itemprop="url"><%= t 'tos_topic.title' %> </a>
           </span>
         </li>
       <% end %>
-      <% if path = privacy_path.presence %>
+      <% if privacy_policy_url.present? %>
         <li itemscope itemtype='http://schema.org/SiteNavigationElement'>
           <span itemprop='name'>
-            <a href='<%= path %>' itemprop="url"><%= t 'privacy_topic.title' %> </a>
+            <a href='<%= privacy_policy_url %>' itemprop="url"><%= t 'privacy_topic.title' %> </a>
           </span>
         </li>
       <% end %>

app/views/static/show.html.erb

@@ -10,11 +10,11 @@
         <li class='nav-item-faq'><a class='<%= @page == 'faq' ? 'active' : '' %>' href='<%=faq_path%>'><%= t 'js.faq' %></a></li>
       <% end %>
     <% end %>
-    <% if path = tos_path.presence %>
-      <li class='nav-item-tos'><a href='<%= path %>' class='<%= @page == 'tos' ? 'active' : '' %>'><%= t 'js.tos' %></a></li>
+    <% if tos_url.present? %>
+      <li class='nav-item-tos'><a href='<%= tos_url %>' class='<%= @page == 'tos' ? 'active' : '' %>'><%= t 'js.tos' %></a></li>
     <% end %>
-    <% if path = privacy_path.presence %>
-      <li class='nav-item-privacy'><a href='<%= path %>' class='<%= @page == 'privacy' ? 'active' : '' %>'><%= t 'js.privacy' %></a></li>
+    <% if privacy_policy_url.present? %>
+      <li class='nav-item-privacy'><a href='<%= privacy_policy_url %>' class='<%= @page == 'privacy' ? 'active' : '' %>'><%= t 'js.privacy' %></a></li>
     <% end %>
   </ul>
 

config/initializers/014-track-setting-changes.rb

@@ -66,6 +66,8 @@
 
   Emoji.clear_cache && Discourse.request_refresh! if name == :emoji_deny_list
 
+  Discourse.clear_urls! if %i[tos_topic_id privacy_topic_id].include?(name)
+
   # Update seeded topics
   if %i[title site_description].include?(name)
     topics = SeedData::Topics.with_default_locale

lib/configurable_urls.rb

@@ -5,19 +5,11 @@ def faq_path
     SiteSetting.faq_url.blank? ? "#{Discourse.base_path}/faq" : SiteSetting.faq_url
   end
 
-  def tos_path
-    if SiteSetting.tos_url.present?
-      SiteSetting.tos_url
-    elsif SiteSetting.tos_topic_id > 0 && Topic.exists?(id: SiteSetting.tos_topic_id)
-      "#{Discourse.base_path}/tos"
-    end
+  def tos_url
+    Discourse.tos_url
   end
 
-  def privacy_path
-    if SiteSetting.privacy_policy_url.present?
-      SiteSetting.privacy_policy_url
-    elsif SiteSetting.privacy_topic_id > 0 && Topic.exists?(id: SiteSetting.privacy_topic_id)
-      "#{Discourse.base_path}/privacy"
-    end
+  def privacy_policy_url
+    Discourse.privacy_policy_url
   end
 end

lib/discourse.rb

@@ -597,6 +597,46 @@ class << self
     alias_method :base_url_no_path, :base_url_no_prefix
   end
 
+  def self.urls_cache
+    @urls_cache ||= DistributedCache.new("urls_cache")
+  end
+
+  def self.tos_url
+    if SiteSetting.tos_url.present?
+      SiteSetting.tos_url
+    else
+      urls_cache["tos"] ||= (
+        if SiteSetting.tos_topic_id > 0 && Topic.exists?(id: SiteSetting.tos_topic_id)
+          "#{Discourse.base_path}/tos"
+        else
+          :nil
+        end
+      )
+
+      urls_cache["tos"] != :nil ? urls_cache["tos"] : nil
+    end
+  end
+
+  def self.privacy_policy_url
+    if SiteSetting.privacy_policy_url.present?
+      SiteSetting.privacy_policy_url
+    else
+      urls_cache["privacy_policy"] ||= (
+        if SiteSetting.privacy_topic_id > 0 && Topic.exists?(id: SiteSetting.privacy_topic_id)
+          "#{Discourse.base_path}/privacy"
+        else
+          :nil
+        end
+      )
+
+      urls_cache["privacy_policy"] != :nil ? urls_cache["privacy_policy"] : nil
+    end
+  end
+
+  def self.clear_urls!
+    urls_cache.clear
+  end
+
   LAST_POSTGRES_READONLY_KEY = "postgres:last_readonly"
 
   READONLY_MODE_KEY_TTL ||= 60

lib/post_destroyer.rb

@@ -90,6 +90,9 @@ def destroy
       UserActionManager.topic_destroyed(@topic)
       DiscourseEvent.trigger(:topic_destroyed, @topic, @user)
       WebHook.enqueue_topic_hooks(:topic_destroyed, @topic, topic_payload) if has_topic_web_hooks
+      if SiteSetting.tos_topic_id == @topic.id || SiteSetting.privacy_topic_id == @topic.id
+        Discourse.clear_urls!
+      end
     end
   end
 
@@ -122,6 +125,9 @@ def recover
         )
       end
       update_imap_sync(@post, false)
+      if SiteSetting.tos_topic_id == @topic.id || SiteSetting.privacy_topic_id == @topic.id
+        Discourse.clear_urls!
+      end
     end
   end