ideqta e mysql high availability i dynamic dns
ako nqkoi mu e interesno... ima kakvo da se dorazviva

#!/bin/sh

mysql_admin=`which mysqladmin`
mysql_user="checker"

HOSTS[0]="192.168.0.12"
HOSTS[1]="192.168.0.13"
HOSTS[2]="192.168.0.14"

HA_HOST="mysql.home.box"
HA_HOST_UPDATE_KEY="/etc/dnssec/Kmysql.home.box.
+157+40039.key"

# checks target if service: 1-up,0-down
function check_target() {
  result=0
  target=$1
  if [ -n $target ]; then
     # ping test method
     count=$(ping -W1 -c1 $target | grep 'received' | 
awk -F',' '{ print $2 }'  | awk '{ print $1 }')
     if [ $count -eq 1 ]; then
        result=1
     fi
     # mysql test method
     # mysqladmin -h${HA_HOST} -u${mysql_user} ping 
&>/dev/null
     # if [ $? -eq 0 ]; then
     #    result=1
     # fi
  fi
  echo $result
}

# update dynamic dns record: 1-success,0-fail
function update_dns() {
  result=0
  hostip=$1
  if [ -n $hostip ]; then
     update_cmd="update delete ${HA_HOST}. A\nupdate add 
${HA_HOST}. 300 A $hostip\nsend"
     echo -e $update_cmd | nsupdate -k 
${HA_HOST_UPDATE_KEY} &>/dev/null
     if [ $? == 0 ]; then
 	result=1
     fi
  fi
  echo $result
}

### Main ###

# get ip address of the ha_host
HA_HOST_IP=$(host $HA_HOST | grep -v "not found" | awk '{ 
print $4; }')
if [ -z $HA_HOST_IP ]; then
   echo "error: cannot resolve hostname $HA_HOST"
   # alert about the problem
   exit
fi

# check if "alive"
target=$HA_HOST_IP
if [ $(check_target $target) == 0 ]; then
   echo "$HA_HOST[$HA_HOST_IP] is down!"
   NEW_HA_HOST_IP=0

   # check each backup host
   for host in ${HOSTS[@]} 
     do 
       if [ $host != $HA_HOST_IP ]; then
	  if [ $(check_target $host) -eq 1 ]; then
             NEW_HA_HOST=$host
	     break
          fi
       fi
     done

   # update dns record to new found backup
   if [ $NEW_HA_HOST != 0 ]; then
      if [ $(update_dns $NEW_HA_HOST) -eq 1 ]; then
         echo "update successful for $NEW_HA_HOST"
      else
         echo "update failed for $NEW_HA_HOST"
      fi
   else
      echo "no new host found"
      # alert about the problem
   fi
fi