# File lib/chef/knife/ssh.rb, line 85
      def session
        ssh_error_handler = Proc.new do |server|
          if config[:manual]
            node_name = server.host
          else
            @action_nodes.each do |n|
              node_name = n if format_for_display(n)[config[:attribute]] == server.host
            end
          end
          ui.warn "Failed to connect to #{node_name} -- #{$!.class.name}: #{$!.message}"
          $!.backtrace.each { |l| Chef::Log.debug(l) }
        end

        @session ||= Net::SSH::Multi.start(:concurrent_connections => config[:concurrency], :on_error => ssh_error_handler)
      end