clear_reloadable_connections

# File activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb, line 444
      def clear_reloadable_connections(raise_on_acquisition_timeout = true)
        num_new_conns_required = 0

        with_exclusively_acquired_all_connections(raise_on_acquisition_timeout) do
          synchronize do
            @connections.each do |conn|
              checkin conn
              conn.disconnect! if conn.requires_reloading?
            end
            @connections.delete_if(&:requires_reloading?)

            @available.clear

            if @connections.size < @size
              # because of the pruning done by this method, we might be running
              # low on connections, while threads stuck in queue are helpless
              # (not being able to establish new connections for themselves),
              # see also more detailed explanation in +remove+
              num_new_conns_required = num_waiting_in_queue - @connections.size
            end

            @connections.each do |conn|
              @available.add conn
            end
          end
        end

        bulk_make_new_connections(num_new_conns_required) if num_new_conns_required > 0
      end