Expire dashboard data when you upgrade to a new discourse version. Version check data was being cached and causing confusion to people who upgraded.

app/controllers/admin/dashboard_controller.rb

@@ -1,9 +1,16 @@
 class Admin::DashboardController < Admin::AdminController
 
-  caches_action :index, expires_in: 1.hour
-
   def index
-    render_json_dump(AdminDashboardData.fetch_all)
+    # see https://github.com/rails/rails/issues/8167
+    # TODO: after upgrading to Rails 4, try to remove "if cache_classes"
+    if Discourse::Application.config.cache_classes
+      dashboard_data = Rails.cache.fetch("admin-dashboard-data-#{Discourse::VERSION::STRING}", expires_in: 1.hour) do
+        AdminDashboardData.fetch_all.as_json
+      end
+      render json: dashboard_data
+    else
+      render_json_dump AdminDashboardData.fetch_all
+    end
   end
 
   def problems