Update the query stats in the footer to track cache hits/misses (WIP)

Update the query stats in the footer to track cache hits and misses per request

app/assets/stylesheets/flash.css

@@ -38,4 +38,14 @@ footer {
 footer:hover {
   background-color: #f5f5f5;
   color: #333;
-} 
+}
+
+.cache-stats {
+  font-size: 12px;
+  color: #666;
+  margin-top: 5px;
+}
+
+.cache-stats span {
+  font-weight: bold;
+}

app/controllers/application_controller.rb

@@ -1,5 +1,6 @@
 class ApplicationController < ActionController::Base
   before_action :set_paper_trail_whodunnit
+  before_action :initialize_cache_counters
 
   # Only allow modern browsers supporting webp images, web push, badges, import maps, CSS nesting, and CSS :has.
   allow_browser versions: :modern
@@ -21,4 +22,17 @@ class ApplicationController < ActionController::Base
       redirect_to root_path, alert: "Please sign in first!"
     end
   end
+
+  def initialize_cache_counters
+    Thread.current[:cache_hits] = 0
+    Thread.current[:cache_misses] = 0
+  end
+
+  def increment_cache_hits
+    Thread.current[:cache_hits] += 1
+  end
+
+  def increment_cache_misses
+    Thread.current[:cache_misses] += 1
+  end
 end

app/helpers/application_helper.rb

@@ -1,2 +1,7 @@
 module ApplicationHelper
+  def cache_stats
+    hits = Thread.current[:cache_hits] || 0
+    misses = Thread.current[:cache_misses] || 0
+    { hits: hits, misses: misses }
+  end
 end

app/views/layouts/application.html.erb

@@ -46,6 +46,7 @@
           Build <%= Rails.application.config.git_version %> from <%= time_ago_in_words(Rails.application.config.server_start_time) %> ago.
           <%= pluralize(Heartbeat.cached_recent_count, 'heartbeat') %> in the last 24 hours.
           (DB: <%= pluralize(QueryCount::Counter.counter, "query") %>, <%= QueryCount::Counter.counter_cache %> cached)
+          (CACHE: <%= cache_stats[:hits] %> hits, <%= cache_stats[:misses] %> misses)
         </p>
       </div>
     </footer>

config/application.rb

@@ -23,5 +23,18 @@ module Harbor
     #
     # config.time_zone = "Central Time (US & Canada)"
     # config.eager_load_paths << Rails.root.join("extras")
+
+    ActiveSupport::Notifications.subscribe('cache_read.active_support') do |*args|
+      event = ActiveSupport::Notifications::Event.new(*args)
+      if event.payload[:hit]
+        Thread.current[:cache_hits] += 1
+      else
+        Thread.current[:cache_misses] += 1
+      end
+    end
+
+    ActiveSupport::Notifications.subscribe('cache_fetch_hit.active_support') do |*args|
+      Thread.current[:cache_hits] += 1
+    end
   end
 end