PERF: use distributed cache for site text and category slugs

app/models/category.rb

@@ -1,3 +1,6 @@
+require_dependency 'distributed_cache'
+require_dependency 'sass/discourse_stylesheets'
+
 class Category < ActiveRecord::Base
 
   include Positionable
@@ -349,10 +352,26 @@ SQL
     id == SiteSetting.uncategorized_category_id
   end
 
+  @@url_cache = DistributedCache.new('category_url')
+
+  after_save do
+    # parent takes part in url calculation
+    # any change could invalidate multiples
+    @@url_cache.clear
+  end
+
   def url
-    url = "/category"
-    url << "/#{parent_category.slug}" if parent_category_id
-    url << "/#{slug}"
+    url = @@url_cache[self.id]
+    unless url
+      url = "/category"
+      url << "/#{parent_category.slug}" if parent_category_id
+      url << "/#{slug}"
+      url.freeze
+
+      @@url_cache[self.id] = url
+    end
+
+    url
   end
 
   # If the name changes, try and update the category definition topic too if it's
@@ -366,7 +385,7 @@ SQL
   end
 
   def publish_discourse_stylesheet
-    MessageBus.publish("/discourse_stylesheet", self.name)
+    DiscourseStylesheets.cache.clear
   end
 end
 

app/models/site_text.rb

@@ -1,18 +1,16 @@
 require_dependency 'site_text_type'
 require_dependency 'site_text_class_methods'
+require_dependency 'distributed_cache'
 
 class SiteText < ActiveRecord::Base
 
-  # needed for site text class methods
-  @mutex = Mutex.new
-  @text_for_cache = {}
   extend SiteTextClassMethods
   self.primary_key = 'text_type'
 
   validates_presence_of :value
 
   after_save do
-    MessageBus.publish '/text_for', self.text_type
+    SiteText.text_for_cache.clear
   end
 
   def self.formats

lib/sass/discourse_stylesheets.rb

@@ -1,4 +1,5 @@
 require_dependency 'sass/discourse_sass_compiler'
+require_dependency 'distributed_cache'
 
 class DiscourseStylesheets
 
@@ -7,35 +8,22 @@ class DiscourseStylesheets
   MANIFEST_FULL_PATH = "#{MANIFEST_DIR}/stylesheet-manifest"
 
   @lock = Mutex.new
-  @links = {}
 
-  def self.ensure_subscribed!
-    unless @subscribed
-      @lock.synchronize do
-        MessageBus.subscribe("/discourse_stylesheet") do |message|
-          @lock.synchronize do
-            @links[message.site_id] = nil
-          end
-        end
-        @subscribed = true
-      end
-    end
+  def self.cache
+    @cache ||= DistributedCache.new("discourse_stylesheet")
   end
 
   def self.stylesheet_link_tag(target = :desktop)
-    ensure_subscribed!
+    tag = cache[target]
+    return tag if tag
+
     @lock.synchronize do
-      links = (@links[RailsMultisite::ConnectionManagement.current_db] ||= {})
-      tag = links[target]
+      builder = self.new(target)
+      builder.compile unless File.exists?(builder.stylesheet_fullpath)
+      builder.ensure_digestless_file
+      tag = %[<link href="#{Rails.env.production? ? builder.stylesheet_relpath : builder.stylesheet_relpath_no_digest + '?body=1'}" media="all" rel="stylesheet" />].html_safe
 
-      if !tag
-        builder = self.new(target)
-        builder.compile unless File.exists?(builder.stylesheet_fullpath)
-        builder.ensure_digestless_file
-        tag = %[<link href="#{Rails.env.production? ? builder.stylesheet_relpath : builder.stylesheet_relpath_no_digest + '?body=1'}" media="all" rel="stylesheet" />].html_safe
-
-        links[target] = tag
-      end
+      cache[target] = tag
 
       tag
     end

lib/site_setting_extension.rb

@@ -289,7 +289,7 @@ module SiteSettingExtension
   protected
 
   def clear_cache!
-    MessageBus.publish '/text_for', 'site_settings'
+    SiteText.text_for_cache.clear
     Rails.cache.delete(SiteSettingExtension.client_settings_cache_key)
   end
 

lib/site_text_class_methods.rb

@@ -15,39 +15,16 @@ module SiteTextClassMethods
     @types << SiteTextType.new(text_type, format, opts)
   end
 
+  def text_for_cache
+    @text_for_cache ||= DistributedCache.new("text_for_cache")
+  end
+
   def text_for(text_type, replacements=nil)
     text = nil
-    text = cached_text_for(text_type) if replacements.blank?
+    text = text_for_cache[text_type] if replacements.blank?
     text ||= uncached_text_for(text_type, replacements)
   end
 
-  def cached_text_for(text_type)
-    ensure_subscribed!
-    @mutex.synchronize do
-      cache = @text_for_cache[RailsMultisite::ConnectionManagement.current_db]
-      cache[text_type] if cache
-    end
-  end
-
-  def store_cached_text_for(text_type, result)
-    ensure_subscribed!
-    @mutex.synchronize do
-      cache = (@text_for_cache[RailsMultisite::ConnectionManagement.current_db] ||= {})
-      cache[text_type] = result
-    end
-  end
-
-  def ensure_subscribed!
-    return if @subscribed
-    @mutex.synchronize do
-      MessageBus.subscribe("/text_for") do |message|
-        @mutex.synchronize do
-          @text_for_cache[message.site_id] = nil
-        end
-      end
-    end
-  end
-
   def uncached_text_for(text_type, replacements=nil)
     store_cache = replacements.blank?
 
@@ -71,7 +48,7 @@ module SiteTextClassMethods
 
     if store_cache
       result.freeze
-      store_cached_text_for(text_type, result)
+      text_for_cache[text_type] = result
     end
 
     result