FIX: Prevent concurrent updates to top_topics (#19854)

to prevent lock timeouts

app/models/top_topic.rb

@@ -5,6 +5,7 @@ class TopTopic < ActiveRecord::Base
 
   # The top topics we want to refresh often
   def self.refresh_daily!
+    DistributedMutex.synchronize("update_top_topics", validity: 5.minutes) do
       transaction do
         remove_invisible_topics
         add_new_visible_topics
@@ -12,15 +13,18 @@ class TopTopic < ActiveRecord::Base
         update_counts_and_compute_scores_for(:daily)
       end
     end
+  end
 
   # We don't have to refresh these as often
   def self.refresh_older!
+    DistributedMutex.synchronize("update_top_topics", validity: 5.minutes) do
       older_periods = periods - %i[daily all]
 
       transaction { older_periods.each { |period| update_counts_and_compute_scores_for(period) } }
 
       compute_top_score_for(:all)
     end
+  end
 
   def self.refresh!
     refresh_daily!