Setting PowerDNS To Ignore Records For Downed Web Sites

 gmysql-any-query=select content,ttl,prio,type,domain_id,name from records where name='%s' and (prio<>-1 or prio is null)

service pdns restart

#!/usr/bin/env ruby
require 'net/http'
require 'rubygems'
require 'activerecord'
 
SITE_ADDRESSES = %w( www.yourdomain.com www.example.com )
SITE_THAT_IS_ALWAYS_UP = "" # some well known site that is always up
 
class Record < ActiveRecord::Base
  ActiveRecord::Base.establish_connection(:adapter => "mysql",
    :encoding => "utf8", :database => "powerdns_production",
    :username => "your_mysql_username", :password => "your_secret_password_here",
    :host => "ns1.your_isp.com")
  set_inheritance_column :ruby_type
end
 
$running = true
 
def signal_trap_exit(signal_name)
  puts "#{Time.now} received #{signal_name} signal"
  $running = false
end
 
our_exit_signals = ["TERM", "INT", "KILL", "HUP"]
for exit_signal_name in our_exit_signals
  Signal.trap(exit_signal_name, "signal_trap_exit('#{exit_signal_name}')")
end
 
def check_internet
  begin
    Timeout::timeout(5) do
      Net::HTTP.get_response(SITE_THAT_IS_ALWAYS_UP, "/", 80) do |response|
        return response.code.match(/2|3\d{2}/)
      end
    end
  rescue => e
    puts "#{Time.now} Error connecting to internet: #{e}"
    return false
  end
end
 
def get_site_ip_addresses
  begin
    Record.find(:all, :conditions => ["type = ? and name in (?)", "A", SITE_ADDRESSES])
  rescue => e
    puts "#{Time.now} Error finding all records: #{e}"
    return []
  end
end
 
def make_inactive(ip_record)
  Record.update_all("prio=-1", "name='#{ip_record.name}' and content='#{ip_record.content}'")
end
 
def make_active(ip_record)
  Record.update_all("prio=1", "name='#{ip_record.name}' and content='#{ip_record.content}'")
end
 
while($running) do
  get_site_ip_addresses.each do |ip_address|
    begin
      Timeout::timeout(5) do
        Net::HTTP.get_response(ip_address.content.to_s, "/", 80) do |response|
          puts "#{Time.now} Response code for #{ip_address.content.to_s}: #{response.code}"
          make_active(ip_address) if ip_address.prio == -1
        end
      end
    rescue => e
      puts "#{Time.now} Error connecting to #{ip_address.content.to_s}: #{e}"
      if check_internet
        make_inactive(ip_address) unless ip_address.prio == -1
      end
    end
  end
 
  sleep 15 if $running
end