Memoise database load balancing status

This sampler runs every few seconds, and in development mode, it can
flood the console with license load messages. This value can only change
during the lifetime of the sampler if someone uploads a new license, or
a license expires, but those are both pretty rare (and would need
associated configuration changes anyway).

ee/lib/ee/gitlab/metrics/samplers/database_sampler.rb

@@ -5,8 +5,12 @@ module EE
     module Metrics
       module Samplers
         module DatabaseSampler
+          extend ::Gitlab::Utils::Override
+          include ::Gitlab::Utils::StrongMemoize
+
           private
 
+          override :host_stats
           def host_stats
             super
               .concat(geo_connection_stats)
@@ -20,7 +24,7 @@ module EE
           end
 
           def load_balancing_connection_stats
-            return [] unless ::Gitlab::Database::LoadBalancing.enable?
+            return [] unless load_balancing_enabled?
 
             ActiveRecord::Base.connection.load_balancer.host_list.hosts.map do |host|
               {
@@ -29,6 +33,12 @@ module EE
               }
             end
           end
+
+          def load_balancing_enabled?
+            strong_memoize(:load_balancing_enabled) do
+              ::Gitlab::Database::LoadBalancing.enable?
+            end
+          end
         end
       end
     end