Add logs for action taken

lib/gitlab/background_migration/update_authorized_keys_file_since.rb

@@ -26,6 +26,8 @@ module Gitlab
 
       # Not added to Gitlab::Shell because I don't expect this to be used again
       def batch_add_keys_in_db_starting_from(start_id)
+        Rails.logger.info("Adding all keys starting from ID: #{start_id}")
+
         gitlab_shell.batch_add_keys do |adder|
           Key.find_each(start: start_id, batch_size: 1000) do |key|
             adder.add_key(key.shell_id, key.key)

lib/gitlab/shell.rb

@@ -247,6 +247,8 @@ module Gitlab
     def remove_keys_not_found_in_db
       return unless self.authorized_keys_enabled?
 
+      Rails.logger.info("Removing keys not found in DB")
+
       batch_read_key_ids do |ids_in_file|
         ids_in_file.uniq!
         keys_in_db = Key.where(id: ids_in_file)
@@ -255,6 +257,7 @@ module Gitlab
 
         ids_to_remove = ids_in_file - keys_in_db.pluck(:id)
         ids_to_remove.each do |id|
+          Rails.logger.info("Removing key-#{id} not found in DB")
           remove_key("key-#{id}")
         end
       end