    # File lib/phusion_passenger/abstract_server_collection.rb, line 194
            def register_activity(server)
                    must_be_in_synchronize_block
                    if eligable_for_cleanup?(server)
                            if server.next_cleaning_time == @next_cleaning_time
                                    @next_cleaning_time = nil
                            end
                            server.next_cleaning_time = Time.now + server.max_idle_time
                    end
            end