keepalived实现redis双机高可用

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　　现在的生产环境基本上都采用主备方式，而如何实现redis的主备呢？一般情况下，redis实现主从复制比较简单，只需要在从服务器的配置文件里配置 "slaveof"即可。但这样存在一个问题：主服务器挂掉时，可临时将业务地址转移到从服务器，但从服务器无法进行写操作。

　　为解决这个问题，在网上查找了一些资料。主要有以下几种方案
　　1、使用keepalived+监控脚本实现主备切换
　　2、使用redis cluster实现双主切换，原理就是模仿MySQL的bin-log机制。

　　本文介绍一下第1种方案


　　设计思路:
　　当 Master 与 Slave 均运作正常时, Master负责服务，Slave负责Standby；
　　当 Master 挂掉，Slave 正常时, Slave接管服务，同时关闭主从复制功能；
　　当 Master 恢复正常，则从Slave同步数据，同步数据之后关闭主从复制功能，恢复Master身份，于此同时Slave等待Master同步数据完成之后，恢复Slave身份。
　　然后依此循环。


　　环境介绍:
　　Master:  192.168.2.23
　　Slave:   192.168.2.24
　　VIP:    192.168.2.40

　　操作系统：
　　CentOS 6.5 64bit

　　软件版本：
　　redis 3.2.0

　　keepalived 1.2.13　　

　　实施步骤:

　　一、搭建redis主从
　　1、用saltstack部署redis到主从节点（略）
　　2、修改redis从节点的配置文件：
　　增加以下一行：
　　slaveof  192.168.2.40 6379
　　二、配置keepalived
　　1、Master和Slave两台主机上分别安装keepalived服务

　　yum -y install keepalived
　　2、修改keepalived配置文件

　　Master:
　　cat /etc/keepalived/keepalived.conf

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! Configuration File for keepalived vrrp_script chk_redis {      script "/etc/keepalived/scripts/check_redis.sh"      interval 5      weight 20      } vrrp_instance VI_REDIS_1 {     #state BACKUP     state MASTER     interface eno16780032     virtual_router_id 30     mcast_src_ip 192.168.2.23     priority 100     advert_int 1     authentication {        auth_type PASS        auth_pass 11111       } track_script {         chk_redis      }     notify_master /etc/keepalived/scripts/master.sh     notify_backup /etc/keepalived/scripts/backup.sh     notify_stop /etc/keepalived/scripts/stop.sh     notify_fault /etc/keepalived/scripts/fault.sh     virtual_ipaddress {        192.168.2.40     } }

　　Slave:
　　cat /etc/keepalived/keepalived.conf

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! Configuration File for keepalived vrrp_script chk_redis {      script "/etc/keepalived/scripts/check_redis.sh"      interval 5      weight 20      } vrrp_instance VI_REDIS_1 {     #state BACKUP     state MASTER     interface eno16780032     virtual_router_id 30     mcast_src_ip 192.168.2.24     priority 100     advert_int 1     authentication {        auth_type PASS        auth_pass 11111       } track_script {         chk_redis      }     notify_master /etc/keepalived/scripts/master.sh     notify_backup /etc/keepalived/scripts/backup.sh     notify_stop /etc/keepalived/scripts/stop.sh     notify_fault /etc/keepalived/scripts/fault.sh     virtual_ipaddress {        192.168.2.40     } }

　　3、编写脚本
　　首先在两台服务器分别创建监控redis的脚本
　　cat /etc/keepalived/scripts/check_redis.sh

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#!/bin/bash count=1 LOGFILE="/var/log/keepalived-redis-state.log" while true do /usr/local/redis/bin/redis-cli -p 6379 -a abcd*123456 ping >/dev/null 2>&1 i=$? netstat -ntlup | grep 6379 >/dev/null 2>&1 j=$? if [ $i = 0 -a $j = 0 ];then         exit 0 else         if [ $count -gt 10 ]; then                 echo "`hostname` redis check is failed,Exit check script....." >>$LOGFILE                 break         fi         sleep 1         let count++         continue fi done /etc/init.d/keepalived stop

　　然后是以下这些脚本的用途
　　notify_master /etc/keepalived/scripts/master.sh
　　notify_backup /etc/keepalived/scripts/backup.sh
　　notify_stop /etc/keepalived/scripts/stop.sh
　　notify_fault /etc/keepalived/scripts/fault.sh
　　当keepalived进入Master状态时，会执行notify_master;
　　当keepalived进入Backup状态时，会执行notify_backup;
　　当keepalived进入fault状态时，会执行notify_fault ；
　　当keepalived进入stop状态时，会执行notify_stop；

　　在Master、Slave服务器上编写以下4个脚本

　　cat /etc/keepalived/scripts/master.sh

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#!/bin/bash REDISCLI="/usr/local/redis/bin/redis-cli" LOGFILE="/var/log/keepalived-redis-state.log" echo "[master]" >> $LOGFILE echo "`date +%Y-%m-%d' '%H:%M:%S`" >> $LOGFILE echo " change to master role ..." >> $LOGFILE nohup /bin/bash /usr/local/shell/change_master.sh  & while true do         /bin/bash /usr/local/shell/role_check.sh |grep slave   >> $LOGFILE         if [ $? -eq 0 ];then                 nohup /bin/bash /usr/local/shell/change_master.sh  &         else                 exit 0         fi         sleep 5    done

　　cat /etc/keepalived/scripts/backup.sh

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#!/bin/bash REDISCLI="/usr/local/redis/bin/redis-cli" LOGFILE="/var/log/keepalived-redis-state.log" echo "[backup]" >> $LOGFILE echo "`date +%Y-%m-%d' '%H:%M:%S`" >> $LOGFILE echo " change to slave role ..." >> $LOGFILE sleep 20 nohup /bin/bash /usr/local/shell/change_slave.sh  & while true do /bin/bash /usr/local/shell/role_check.sh |grep master   >> $LOGFILE if [ $? -eq 0 ];then nohup /bin/bash /usr/local/shell/change_slave.sh  & else exit 0 fi sleep 5    done

　　cat /etc/keepalived/scripts/stop.sh

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#!/bin/bash log='/var/log/keepalived-redis-state.log' Host=`hostname` echo "`date +%Y-%m-%d' '%H:%M:%S` :`hostname` keepalived service stop ... " >> $log

　　cat /etc/keepalived/scripts/fault.sh

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#!/bin/bash log='/var/log/keepalived-redis-state.log' echo "`date +%Y-%m-%d' '%H:%M:%S` : fault ..." >> $log

　　在Master、Slave服务器上编写以下4个故障切换脚本

　　cat /usr/local/shell/change_master.sh

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#!/bin/bash PWD=abcd*123456 MASTER_IP=192.168.2.40 port=(6379) for PORT in ${port } do /usr/local/redis/bin/redis-cli -p $PORT -a $PWD SLAVEOF NO ONE done

　　cat /usr/local/shell/change_slave.sh

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#!/bin/bash PWD=abcd*123456 MASTER_IP=192.168.2.40 port=(6379) for PORT in ${port } do /usr/local/redis/bin/redis-cli -p $PORT -a $PWD SLAVEOF $MASTER_IP $PORT done

　　cat /usr/local/shell/startredis.sh

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#!/bin/bash port=(6379) for PORT in ${port } do /etc/init.d/redis_$PORT  start done

　　cat /usr/local/shell/stopredis.sh

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#!/bin/bash port=(6379) for PORT in ${port } do /etc/init.d/redis_$PORT  stop done

　　cat /usr/local/shell/restartredis.sh

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#!/bin/bash port=(6379) for PORT in ${port } do /etc/init.d/redis_$PORT  restart done

　　cat /usr/local/shell/role_check.sh

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#!/bin/bash PWD=abcd*123456 MASTER_IP=192.168.2.40 port=(6379) for PORT in ${port } do /usr/local/redis/bin/redis-cli -p $PORT -a $PWD info|egrep   "role|tcp_port" done