Quick and to the point IP Failover

failoverd.rb

#!/usr/local/bin/ruby 
#
# File: failoverd.rb
# Description: Daemon to handle failover and restart
# Date: 12-14-2009 - Luke van der Hoeven
#
# Credit: Based on Patrick Hennessy's ipfaild.pl script
#   (http://git.pathennessy.com/cgi-bin/gitweb.cgi?p=linux-scripts.git;a=blob;f=ipfaild.pl;hb=HEAD)
#

require 'rubygems'
require 'daemons'
require 'syslog'
require 'ping'
require 'action_mailer'
 
## For email notifications ##
ActionMailer::Base.delivery_method = :smtp
ActionMailer::Base.smtp_settings = {
 :address  => "ptvlmail2.hargray.org",
 :port     => 25
}
 
class Emailer < ActionMailer::Base
  def failover
    subject    "Primary Production Server Down!!"
    from       "[email protected]"
    recipients "[email protected]"
    body	"ITWEBPUB1 is down. Failing over to ITWEBPUB2.\nPlease inspect the primary server and restore order to the galaxy."
  end
end

## File IO Paths ##
@program_name = "failoverd"
@daemon_lock_file = "/var/run/#{@program_name}/#{@program_name}.lock"

## Executable paths ##
@ifconfig = '/sbin/ifconfig'
@send_arp = '/usr/sbin/send_arp'
@apache2ctl = '/usr/sbin/apachectl'

## Configuration params ##
@ping_timeout = 1
@sleep_time = 2
@fail_threshold
@missed = 0
@is_live = false
@active = true

## Server config ##
@other_server = "itwebpub1"
@this_mac = "00:1E:C9:5C:A7:9B"

@ip_records = [
 {:name => "foobar", :ip => "192.168.120.57", :dev => "eth0:0", :mask => "255.255.255.0" }  
]

#function for loading the VIP 
def ifconfig_down
   for record in @ip_records
      Syslog.info("Running: #{@ifconfig} #{record[:dev]} down")
      unless system("#{@ifconfig} #{record[:dev]} down")
         Syslog.info("Error: #{$!} \"#{@ifconfig} #{record[:dev]} down\" failed.")
      end
   end
end

Daemons.run_proc('failoverd.rb') do
   f = File.new(@daemon_lock_file, 'w+')
   if(f == 0)
      warn "#{@program_name}: Couldn't open #{@daemon_lock_file}"
      exit(0)
   end

   #put the process id into a the pid file
   f.write Process.pid
   #open the system log
   Syslog.open(@program_name, Syslog::LOG_PID, Syslog::LOG_DAEMON)
   
   #handle all termination signals
   Signal.trap("HUP") do
      Syslog.info("#{@program_name} caught SIGHUP")
      @active = false
   end
   Signal.trap("INT") do
      Syslog.info("#{@program_name} caught SIGINT")
      @active = false
   end
   Signal.trap("QUIT") do
      Syslog.info("#{@program_name} caught SIGQUIT")
      @active = false
   end
   Signal.trap("TERM") do
      Syslog.info("#{@program_name} caught SIGTERM")
      @active = false
   end
   
   #initialize by releasing the VIP
   ifconfig_down
   
   #main loop
   while @active
      unless Ping.pingecho(@other_server, @ping_timeout) #no response
         @missed += 1
      else
         if @missed > @fail_threshold
            ifconfig_down  #primary is back, release VIP
            @is_live = false
            @missed = 0
         end
      end
      
      if @missed == @fail_threshold and !@is_live
         @is_live = true   #primary is down, load VIP
         for record in @ip_records
   			Syslog.info("Running: #{@ifconfig} #{record[:dev]} #{record[:ip]} netmask #{record[:mask]}")
   			unless system("#{@ifconfig} #{record[:dev]} #{record[:ip]} netmask #{record[:mask]}")
   			   Syslog.info("Error: #{$!} \"#{@ifconfig} #{record[:dev]} #{record[:ip]} netmask #{record[:mask]}")
            end
            #notify IP tables
   			Syslog.info("Running: #{@send_arp} #{record[:ip]} #{@this_mac} #{record[:ip]} ff:ff:ff:ff:ff:ff")
   			unless system("#{@send_arp} #{record[:ip]} #{@this_mac} #{record[:ip]} ff:ff:ff:ff:ff:ff")
   			   Syslog.info("Error: #{$!} \"#{@send_arp} #{record[:ip]} #{@this_mac} #{record[:ip]} ff:ff:ff:ff:ff:ff\"")
			   end
   		end
   		
   		#restart apache
   		Syslog.info("Running: #{@apache2ctl} -k restart")
   		unless system("#{@apache2ctl} -k restart")
   		   Syslog.info("Error: #{$!} \"#{@apache2ctl} -k restart\"")
   		end
   		
   		#send email notification of server down
   		Emailer.deliver_failover
   	end
   	
   	sleep @sleep_time
	end
	
   #release VIP if shutting down failover
   ifconfig_down
   Syslog.close
   f.close
   exit(0)
end

gistfile2.txt

#run with the command
#only needs to be run on the backup server
[ruby |./]failoverd.rb start|stop|restart|run