count the number of specific migration background jobs

bin/scripts/02_failover/060_go/p02/030-await-sidekiq-drain.rb

@@ -27,8 +27,12 @@ def cronjob_can_be_disabled(cron_name)
 end
 
 def handle_named_set(title, named_set)
+  background_migrations = {}
   queue_sizes = named_set.each_with_object({}) do |job, hash|
     hash[job.queue] = (hash[job.queue] || 0) + 1
+    if job.queue == 'background_migration'
+      background_migrations[job.args[0]] = (background_migrations[job.args[0]] || 0) + 1
+    end
   end
 
   if !queue_sizes.empty?
@@ -37,6 +41,9 @@ def handle_named_set(title, named_set)
     queue_sizes.each do |k,v|
       status = queue_can_be_purged(k) ? " (purged)" : ""
       puts "  #{k}: #{v}#{status}"
+      if k == 'background_migration' && !background_migrations.empty?
+        background_migrations.each { |klass, count| puts "    #{klass}: #{count}"}
+      end
     end
   end