executing 'ruby -e "r = rand(10); puts %{sleep #{r}}; sleep r"'
 ** [out :: dbadmin1] sleep 6
 ** [out :: app1] sleep 4
 ** [out :: work1] sleep 2
 ** [out :: mirror1] sleep 5
 ** Server dbadmin1 finished command in 4 seconds
 ** Server app1 finished command in 7 seconds

module PerServerTime
  # set via Capistrano::Command.per_server_time_threshold = 111
  def self.included(base)
    class << base
      attr_accessor :per_server_time_threshold
    end
  end

  # whenever a command finishes on 1 server print how long it ran on this server
  def process_iteration
    return super if @channels.size < 2 # do not need per-server logging for 1 server

    @start_time ||= Time.now.to_f
    @closed_channels ||= []

    @channels.each do |channel|
      if channel[:closed] && !@closed_channels.include?(channel)
        @closed_channels < (self.class.per_server_time_threshold || 30)
          host = channel.connection.instance_variable_get(:@xserver).host
          logger.info("Server #{host} finished command in #{time} seconds")
        end
      end
    end

    super
  end
end

Capistrano::Command.send(:include, PerServerTime)