Redis 虚拟IP切换

在sentinel进行切换时还会自动调用一个脚本（如果设置的话），做一些自动化操作，比如如果我们需要一个虚拟IP永远飘在Master上（这个VIP可不是被应用用来连接redis 的，用过的人都知道连接redis sentinel并不依赖于VIP的），那么可以在sentinel配置文件中配置：

sentinel client-reconfig-script mymaster /redis/script/failover.sh 

在发生主从切换，Master发生变化时，该脚本会被sentinel进行调用，调用的参数如其配置文件所描述的：

# The following arguments are passed to the script: # # <master-name> <role> <state> <from-ip> <from-port> <to-ip> <to-port> # # <state> is currently always "failover" # <role> is either "leader" or "observer" #  # The arguments from-ip, from-port, to-ip, to-port are used to communicate # the old address of the master and the new address of the elected slave # (now a master). 

因此，我们可以在failover.sh中进行判断，如果该脚本所运行的主机IP等于新的Master IP，那么将VIP加上，如果不等于，则该机器为Slave，就去掉VIP。通过这种方式进行VIP的切换：

#!/bin/sh _DEBUG="on" DEBUGFILE=/tmp/sentinel_failover.log VIP='192.168.2.120' MASTERIP=${6} MASK='24' IFACE='eno33554960' MYIP=$(ip -4 -o addr show dev ${IFACE}| grep -v secondary| awk '{split($4,a,"/");print a[1]}')  DEBUG () {         if [ "$_DEBUG" = "on" ]; then                 echo `$@` >>  ${DEBUGFILE}         fi }  set -e DEBUG date  DEBUG echo $@   DEBUG echo "Master: ${MASTERIP} My IP: ${MYIP}" if [ ${MASTERIP} = ${MYIP} ]; then         if [ $(ip addr show ${IFACE} | grep ${VIP} | wc -l) = 0 ]; then                 /sbin/ip addr add ${VIP}/${MASK} dev ${IFACE}         DEBUG date                 DEBUG echo "/sbin/ip addr add ${VIP}/${MASK} dev ${IFACE}"         DEBUG date         DEBUG echo "IP Arp cleaning: /usr/sbin/arping -q -f -c 1 -A ${VIP} -I ${IFACE}"                  /usr/sbin/arping -q -f -c 1 -A ${VIP} -I ${IFACE}         DEBUG date          DEBUG echo "IP Failover finished!"         fi         exit 0 else         if [ $(ip addr show ${IFACE} | grep ${VIP} | wc -l) != 0 ]; then                 /sbin/ip addr del ${VIP}/${MASK} dev ${IFACE}                 DEBUG echo "/sbin/ip addr del ${VIP}/${MASK} dev ${IFACE}"         fi         exit 0 fi exit 1 

最早这样的用法是一个日本人写的blog，请参见：http://blog.youyo.info/blog/2014/05/24/redis-cluster/