DEV: use Discourse.cache over Rails.cache

Discourse.cache is a more consistent method to use and offers clean fallback
if you are skipping redis

This is part of a larger change that both optimizes Discoruse.cache and omits
use of setex on $redis in favor of consistently using discourse cache

Bench does reveal that use of Rails.cache and Discourse.cache is 1.25x slower
than redis.setex / get so a re-implementation will follow prior to porting

app/models/theme.rb

@@ -418,7 +418,7 @@ class Theme < ActiveRecord::Base
   end
 
   def cached_settings
-    Rails.cache.fetch("settings_for_theme_#{self.id}", expires_in: 30.minutes) do
+    Discourse.cache.fetch("settings_for_theme_#{self.id}", expires_in: 30.minutes) do
       hash = {}
       self.settings.each do |setting|
         hash[setting.name] = setting.value
@@ -438,7 +438,7 @@ class Theme < ActiveRecord::Base
   end
 
   def clear_cached_settings!
-    Rails.cache.delete("settings_for_theme_#{self.id}")
+    Discourse.cache.delete("settings_for_theme_#{self.id}")
   end
 
   def included_settings

app/models/topic_embed.rb

@@ -228,7 +228,7 @@ class TopicEmbed < ActiveRecord::Base
   end
 
   def self.expanded_for(post)
-    Rails.cache.fetch("embed-topic:#{post.topic_id}", expires_in: 10.minutes) do
+    Discourse.cache.fetch("embed-topic:#{post.topic_id}", expires_in: 10.minutes) do
       url = TopicEmbed.where(topic_id: post.topic_id).pluck_first(:embed_url)
       response = TopicEmbed.find_remote(url)
 

lib/discourse.rb

@@ -591,6 +591,7 @@ module Discourse
     SiteSetting.after_fork
     $redis._client.reconnect
     Rails.cache.reconnect
+    Discourse.cache.reconnect
     Logster.store.redis.reconnect
     # shuts down all connections in the pool
     Sidekiq.redis_pool.shutdown { |c| nil }

lib/inline_oneboxer.rb

@@ -14,11 +14,11 @@ class InlineOneboxer
   end
 
   def self.purge(url)
-    Rails.cache.delete(cache_key(url))
+    Discourse.cache.delete(cache_key(url))
   end
 
   def self.cache_lookup(url)
-    Rails.cache.read(cache_key(url))
+    Discourse.cache.read(cache_key(url))
   end
 
   def self.lookup(url, opts = nil)
@@ -70,7 +70,7 @@ class InlineOneboxer
       title: title && Emoji.gsub_emoji_to_unicode(title)
     }
     unless opts[:skip_cache]
-      Rails.cache.write(cache_key(url), onebox, expires_in: 1.day)
+      Discourse.cache.write(cache_key(url), onebox, expires_in: 1.day)
     end
 
     onebox

lib/oneboxer.rb

@@ -51,7 +51,7 @@ module Oneboxer
   end
 
   def self.cached_onebox(url)
-    if c = Rails.cache.read(onebox_cache_key(url))
+    if c = Discourse.cache.read(onebox_cache_key(url))
       c[:onebox]
     end
   rescue => e
@@ -61,7 +61,7 @@ module Oneboxer
   end
 
   def self.cached_preview(url)
-    if c = Rails.cache.read(onebox_cache_key(url))
+    if c = Discourse.cache.read(onebox_cache_key(url))
       c[:preview]
     end
   rescue => e
@@ -71,7 +71,7 @@ module Oneboxer
   end
 
   def self.invalidate(url)
-    Rails.cache.delete(onebox_cache_key(url))
+    Discourse.cache.delete(onebox_cache_key(url))
   end
 
   # Parse URLs out of HTML, returning the document when finished.
@@ -281,7 +281,7 @@ module Oneboxer
   end
 
   def self.external_onebox(url)
-    Rails.cache.fetch(onebox_cache_key(url), expires_in: 1.day) do
+    Discourse.cache.fetch(onebox_cache_key(url), expires_in: 1.day) do
       fd = FinalDestination.new(url,
                               ignore_redirects: ignore_redirects,
                               ignore_hostnames: blacklisted_domains,

lib/search.rb

@@ -137,7 +137,7 @@ class Search
     return 0 unless SiteSetting.search_prefer_recent_posts?
 
     # It can be quite slow to count all the posts so let's cache it
-    Rails.cache.fetch("search-min-post-id:#{SiteSetting.search_recent_posts_size}", expires_in: 1.week) do
+    Discourse.cache.fetch("search-min-post-id:#{SiteSetting.search_recent_posts_size}", expires_in: 1.week) do
       min_post_id_no_cache
     end
   end

lib/site_setting_extension.rb

@@ -192,7 +192,7 @@ module SiteSettingExtension
   end
 
   def client_settings_json
-    Rails.cache.fetch(SiteSettingExtension.client_settings_cache_key, expires_in: 30.minutes) do
+    Discourse.cache.fetch(SiteSettingExtension.client_settings_cache_key, expires_in: 30.minutes) do
       client_settings_json_uncached
     end
   end
@@ -432,7 +432,7 @@ module SiteSettingExtension
   protected
 
   def clear_cache!
-    Rails.cache.delete(SiteSettingExtension.client_settings_cache_key)
+    Discourse.cache.delete(SiteSettingExtension.client_settings_cache_key)
     Site.clear_anon_cache!
   end
 

script/benchmarks/cache/bench.rb

@@ -0,0 +1,81 @@
+# frozen_string_literal: true
+
+require 'benchmark/ips'
+require File.expand_path('../../../../config/environment', __FILE__)
+
+Benchmark.ips do |x|
+
+  x.report("redis setex string") do |times|
+    while times > 0
+      $redis.setex("test_key", 60, "test")
+      times -= 1
+    end
+  end
+
+  x.report("redis setex marshal string") do |times|
+    while times > 0
+      $redis.setex("test_keym", 60, Marshal.dump("test"))
+      times -= 1
+    end
+  end
+
+  x.report("Discourse cache string") do |times|
+    while times > 0
+      Discourse.cache.write("test_key", "test", expires_in: 60)
+      times -= 1
+    end
+  end
+
+  x.report("Rails cache string") do |times|
+    while times > 0
+      Rails.cache.write("test_key_rails", "test", expires_in: 60)
+      times -= 1
+    end
+  end
+
+  x.compare!
+end
+
+Benchmark.ips do |x|
+  x.report("redis get string") do |times|
+    while times > 0
+      $redis.get("test_key")
+      times -= 1
+    end
+  end
+
+  x.report("redis get string marshal") do |times|
+    while times > 0
+      Marshal.load($redis.get("test_keym"))
+      times -= 1
+    end
+  end
+
+  x.report("Discourse read cache string") do |times|
+    while times > 0
+      Discourse.cache.read("test_key")
+      times -= 1
+    end
+  end
+
+  x.report("Rails read cache string") do |times|
+    while times > 0
+      Rails.cache.read("test_key_rails")
+      times -= 1
+    end
+  end
+
+  x.compare!
+end
+
+# Comparison:
+#   redis setex string:    13250.0 i/s
+# redis setex marshal string:    12866.4 i/s - same-ish: difference falls within error
+# Discourse cache string:    10443.0 i/s - 1.27x  slower
+#   Rails cache string:    10367.9 i/s - 1.28x  slower
+
+# Comparison:
+#     redis get string:    13147.4 i/s
+# redis get string marshal:    12789.2 i/s - same-ish: difference falls within error
+# Rails read cache string:    10486.4 i/s - 1.25x  slower
+# Discourse read cache string:    10457.1 i/s - 1.26x  slower

spec/components/cache_spec.rb

@@ -9,6 +9,11 @@ describe Cache do
     Cache.new
   end
 
+  it "supports float" do
+    cache.write("float", 1.1)
+    expect(cache.read("float")).to eq(1.1)
+  end
+
   it "supports fixnum" do
     cache.write("num", 1)
     expect(cache.read("num")).to eq(1)

spec/components/site_setting_extension_spec.rb

@@ -800,7 +800,7 @@ describe SiteSettingExtension do
 
     it 'expires the cache' do
       settings.default_locale = 'zh_CN'
-      expect(Rails.cache.exist?(SiteSettingExtension.client_settings_cache_key)).to be_falsey
+      expect(Discourse.cache.exist?(SiteSettingExtension.client_settings_cache_key)).to be_falsey
     end
 
     it 'refreshes the client' do

spec/requests/onebox_controller_spec.rb

@@ -56,7 +56,7 @@ describe OneboxController do
       stub_request(:get, url).to_return(status: 200, body: html).then.to_raise
 
       bypass_limiting
-      Rails.cache.delete("onebox__#{url}")
+      Discourse.cache.delete("onebox__#{url}")
       get "/onebox.json", params: { url: url }
       expect(response.status).to eq(200)
       expect(response.body).to include("Onebox1")