#!/bin/bash
# Simple reconfigure script to modify multiple nutcracker(twemproxy) servers in case of Redis 
# Failover.

export PATH=/sbin:/usr/local/bin:$PATH

NAME=sentinel
LOGFILE=/opt/sentinel/logs/reconfigure.log
ERRORLOGFILE=/opt/sentinel/logs/reconfigure.error.log
NUTCRACKER_CONF=/opt/nutcracker/etc/nutcracker.yml
NUTCRACKERFAILOVER_CONF=/opt/nutcracker/etc/nutcrackerfailover.yml
NUTCRACKER_PORTs='22121,22123'
MASTER_NAME=$1
ROLE=$2
STATE=$3
FROM_IP=$4
FROM_PORT=$5
TO_IP=$6
TO_PORT=$7
date="$(date -R)"

readonly PROGNAME=sentinel
readonly LOCKFILE_DIR=/tmp
readonly LOCK_FD=200

lock() {
    local prefix=$1
    local fd=${2:-$LOCK_FD}
    local lock_file=$LOCKFILE_DIR/$prefix.lock

    # create lock file
    eval "exec $fd>$lock_file"

    # acquier the lock
    flock -n $fd \
        && return 0 \
        || return 1
}

eexit() {
    local error_str="$@"

    echo $error_str >> ${ERRORLOGFILE}
    exit 1
}

do_nutcracker_reconfig() {
    local old_master_ip=$1
    local old_master_port=$2
    local new_master_ip=$3
    local new_master_port=$4
    local nutcracker_yml=$5

    sed -i s/${old_master_ip}:${old_master_port}/${new_master_ip}:${new_master_port}/g ${nutcracker_yml}
}

do_pause_traffic() {
    local destination_ports=$1
    iptables -I INPUT -p tcp -m multiport --dports ${destination_ports} --syn -j DROP
}

do_release_traffic() {
    local destination_ports=$1
    iptables -D INPUT -p tcp -m multiport --dports ${destination_port} --syn -j DROP
}

do_reload_nutcracker() {
    local service=$1
    local action=$2

    /etc/init.d/$service $action > /dev/null 2>&1
}

check_lock() {
    while : ; do
      [[ -f "/tmp/${PROGNAME}.lock" ]] && break
        lock $PROGNAME \
          || eexit "Only one instance of $PROGNAME can run at one time."
        sleep 0.5
   done
}

main() {

      check_lock

      echo "${date} NUTCRACKER ${MASTER_NAME} PHASE 01: failover triggered from ${FROM_IP}:${FROM_PORT} > ${TO_IP}:${TO_PORT} " >> ${LOGFILE}
      do_nutcracker_reconfig $FROM_IP $FROM_PORT $TO_IP $TO_PORT $NUTCRACKER_CONF

      echo "${date} NUTCRACKER-FAILOVER ${MASTER_NAME} PHASE 02: failover triggered from ${FROM_IP}:${FROM_PORT} > ${TO_IP}:${TO_PORT} " >> ${LOGFILE}
      do_nutcracker_reconfig $FROM_IP $FROM_PORT $TO_IP $TO_PORT $NUTCRACKERFAILOVER_CONF

      do_pause_traffic ${NUTCRACKER_PORTS}

      echo "${date} ${MASTER_NAME} PHASE 03: restarting Nutcracker " >> ${LOGFILE}
      do_reload_nutcracker nutcracker restart

      echo "${date} ${MASTER_NAME} PHASE 04: restarting Nutcracker FAILOVER " >> ${LOGFILE}
      do_reload_nutcracker nutcrackerfailover restart

      do_release_traffic ${NUTCRACKER_PORT}

     echo "${date} ${MASTER_NAME} Failover ended." >> ${LOGFILE}

     # Unlock script
     rm -rf /tmp/${PROGNAME}.lock

     exit 0
}
main