## controller
def update_macs
  @device = Device.find(params[:id])
  @device.process

  if @device.errror_message
    flash[:notice] = @device.error_message
  end

  redirect_to :action => 'show_device', :id => params[:id]
end

## app/models/device.rb
class Device < ActiveRecord::Base
  def error_message
    @error_message
  end

  def process
    if Time.now - self.last_update < UpdateInterval
      @error_message = "Can't call that now."
      return
    end

    master = DeviceMaster.new
    mac_table = master.mac_table(self)
    unless mac_table.blank?
      Mac.delete_all(["device_id = ?", self.id])
      self.update_attribute!(:last_update, Time.now)
    end

    mac_port = master.regexp_mac_port(self)
    port_check = master.regexp_port_check(self)
    mac_separator = master.regexp_mac_separator(self)
    seq_type = master.regexp_mac_port_seq_type(self)

    @mac_table.split("\n").each {|line|
      if line =~ mac_port
        if seq_type == 0
          addr = $1
          port_name = $2
        else
          addr = $2
          port_name = $1
        end

        mac = Mac.new
        mac.address = addr.gsub(mac_separator, '').upcase
        # instead of using port_map, which loads all the ports from the database, we
        # only find the port we need
        mac.port = self.ports.find_by_name(port_name)
        mac.device = self
        mac.save
      end
    }

    check_idle_ports

    self
  rescue Securityerror => msg
    @error_message = msg
  rescue Timeout::Error, Errno::EHOSTUNREACH, SocketError => msg
    @error_message = "No connection to #{self.address}<br/>#{msg}"
  end

  def check_idle_ports
    self.ports.each {|port|
      new_count = port.macs.count

      # check for change
      if new_count != port.macs_count
        if new_count == 0
          port.idle_since = Time.new

          # send notifications to defined mails
          if port.send_notifications
            all_addresses = MailNotification.get_all_addresses
            Mailer.deliver_no_macs(device, port, all_addresses )
          end

        end # if

        port.macs_count = new_count
        port.save!
      end # if
    }
  end
end

## lib/tasks/device_processor.rake
# rake device_processor:process_device ID=6
namespace :device_processor do
  task :process_device do
    # Something like this? *shrug*
    DeviceProcessor.new(ENV["ID"]).process_device
  end
end