bulk_make_new_connections

# File activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb, line 507
        def bulk_make_new_connections(num_new_conns_needed)
          num_new_conns_needed.times do
            # try_to_checkout_new_connection will not exceed pool's @size limit
            if new_conn = try_to_checkout_new_connection
              # make the new_conn available to the starving threads stuck @available Queue
              checkin(new_conn)
            end
          end
        end