network/salt/collectd/dhcpcount.rb

#!/usr/bin/env ruby

require 'date'

INTERVAL = 10
hostname = `hostname`.strip
STDOUT.sync = true

loop do
  seen = {}
  count = 0

  starts = nil
  ends = nil
  ignore = false

  IO::readlines("/var/lib/dhcp/dhcpd.leases").each do |line|
    if line =~ /^lease (.+) \{/
      addr = $1
      ignore = seen[addr]

      seen[addr] = true
      starts = nil
      ends = nil
    elsif line =~ /starts \d+ (.+?);/
      starts = DateTime.parse $1
    elsif line =~ /ends \d+ (.+?);/
      ends = DateTime.parse $1
    elsif line =~ /^\}/
      now = DateTime.now
      if (not ignore) and starts and ends and
         starts <= now and ends >= now and
        count += 1
      end
    end
  end
  puts "PUTVAL \"#{hostname}/exec-dhcpd/current_sessions-leases\" interval=#{INTERVAL} N:#{count}"

  sleep INTERVAL
end