Revert "PERF: use distributed cache for site text and category slugs"

This reverts commit a97f2eee05.

app/models/category.rb

@@ -1,6 +1,3 @@
-require_dependency 'distributed_cache'
-require_dependency 'sass/discourse_stylesheets'
-
 class Category < ActiveRecord::Base
 
   include Positionable
@@ -352,26 +349,10 @@ 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 = @@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
+    url = "/category"
+    url << "/#{parent_category.slug}" if parent_category_id
+    url << "/#{slug}"
   end
 
   # If the name changes, try and update the category definition topic too if it's
@@ -385,7 +366,7 @@ SQL
   end
 
   def publish_discourse_stylesheet
-    DiscourseStylesheets.cache.clear
+    MessageBus.publish("/discourse_stylesheet", self.name)
   end
 end
 

app/models/site_text.rb

@@ -1,16 +1,18 @@
 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
-    SiteText.text_for_cache.clear
+    MessageBus.publish '/text_for', self.text_type
   end
 
   def self.formats

lib/sass/discourse_stylesheets.rb

@@ -1,5 +1,4 @@
 require_dependency 'sass/discourse_sass_compiler'
-require_dependency 'distributed_cache'
 
 class DiscourseStylesheets
 
@@ -8,22 +7,35 @@ class DiscourseStylesheets
   MANIFEST_FULL_PATH = "#{MANIFEST_DIR}/stylesheet-manifest"
 
   @lock = Mutex.new
+  @links = {}
 
-  def self.cache
-    @cache ||= DistributedCache.new("discourse_stylesheet")
+  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
   end
 
   def self.stylesheet_link_tag(target = :desktop)
-    tag = cache[target]
-    return tag if tag
-
+    ensure_subscribed!
     @lock.synchronize do
-      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 = (@links[RailsMultisite::ConnectionManagement.current_db] ||= {})
+      tag = links[target]
 
-      cache[target] = tag
+      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
 
       tag
     end

lib/site_setting_extension.rb

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

lib/site_text_class_methods.rb

@@ -15,16 +15,39 @@ 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 = text_for_cache[text_type] if replacements.blank?
+    text = cached_text_for(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?
 
@@ -48,7 +71,7 @@ module SiteTextClassMethods
 
     if store_cache
       result.freeze
-      text_for_cache[text_type] = result
+      store_cached_text_for(text_type, result)
     end
 
     result