环境介绍:

Master: 192.168.0.1

Slave: 192.168.0.2

Virtural IP Address (VIP): 192.168.0.253


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。

然后依次循环。


需要注意的是,这样做需要在Master与Slave上都开启本地化策略,否则在互相自动切换的过程中,未开启本地化的一方会将另一方的数据清空,造成数据完全丢失。


下面,是具体的实施步骤:


在Master和Slave上安装Keepalived

$ yum install keepalived


修改Master和Slave的/etc/hosts文件

$  vim /etc/hosts


 127.0.0.1   localhost  


 192.168.0.1  redis  


 192.168.0.2  redis-slave 


默认安装完成keepalived之后是没有配置文件的,因此我们需要手动创建:


首先,在Master上创建如下配置文件:

$  vim /etc/keepalived/keepalived.conf


 vrrp_script chk_redis {   


                script "/etc/keepalived/scripts/redis_check.sh"   ###监控脚本   


                interval 2                                        ###监控时间   


 }   


 vrrp_instance VI_1 {   


        state MASTER                            ###设置为MASTER  


         interface eth0                          ###监控网卡      


         virtual_router_id 51  


         priority 101                            ###权重值  


         authentication {   


                      auth_type PASS             ###加密   


                      auth_pass redis            ###密码   


         }   


         track_script {   


                 chk_redis                       ###执行上面定义的chk_redis  


         }   


         virtual_ipaddress {   


              192.168.0.253                         ###VIP   


         }  


         notify_master /etc/keepalived/scripts/redis_master.sh  


         notify_backup /etc/keepalived/scripts/redis_backup.sh  


         notify_fault  /etc/keepalived/scripts/redis_fault.sh  


         notify_stop   /etc/keepalived/scripts/redis_stop.sh   


 } 


然后,在Slave上创建如下配置文件:

$ vim /etc/keepalived/keepalived.conf


 vrrp_script chk_redis {   


                script "/etc/keepalived/scripts/redis_check.sh"   ###监控脚本   


                 interval 2                                        ###监控时间   


 }   


 vrrp_instance VI_1 {   


         state BACKUP                                ###设置为BACKUP   


         interface eth0                              ###监控网卡  


         virtual_router_id 51   


        priority 100                                ###比MASTRE权重值低   


        authentication {   


                      auth_type PASS   


                      auth_pass redis                ###密码与MASTRE相同  


        }   


         track_script {   


                 chk_redis                       ###执行上面定义的chk_redis  


         }   


         virtual_ipaddress {   


              192.168.0.253                         ###VIP   


         }   


         notify_master /etc/keepalived/scripts/redis_master.sh  


         notify_backup /etc/keepalived/scripts/redis_backup.sh  


         notify_fault  /etc/keepalived/scripts/redis_fault.sh  


         notify_stop   /etc/keepalived/scripts/redis_stop.sh   




在Master和Slave上创建监控Redis的脚本

$  mkdir /etc/keepalived/scripts

$  vim /etc/keepalived/scripts/redis_check.sh


#!/bin/bash  


    


0ALIVE=`/opt/redis/bin/redis-cli PING`  


if [ "$ALIVE" == "PONG" ]; then 


echo $ALIVE  


exit 0  


else 


echo $ALIVE  


exit 1  


fi 


编写以下负责运作的关键脚本:

notify_master /etc/keepalived/scripts/redis_master.sh

notify_backup /etc/keepalived/scripts/redis_backup.sh

notify_fault /etc/keepalived/scripts/redis_fault.sh

notify_stop /etc/keepalived/scripts/redis_stop.sh 


因为Keepalived在转换状态时会依照状态来呼叫:

当进入Master状态时会呼叫notify_master

当进入Backup状态时会呼叫notify_backup

当发现异常情况时进入Fault状态呼叫notify_fault

当Keepalived程序终止时则呼叫notify_stop


首先,在Redis Master上创建notity_master与notify_backup脚本:

$  vim /etc/keepalived/scripts/redis_master.sh


#!/bin/bash  


    


REDISCLI="/opt/redis/bin/redis-cli" 


LOGFILE="/var/log/keepalived-redis-state.log" 


    


echo "[master]" >> $LOGFILE  


date >> $LOGFILE  


echo "Being master...." >> $LOGFILE 2>&1  


    


echo "Run SLAVEOF cmd ..." >> $LOGFILE  


$REDISCLI SLAVEOF 192.168.0.2 6379 >> $LOGFILE  2>&1  


sleep 10 #延迟10秒以后待数据同步完成后再取消同步状态  


    


echo "Run SLAVEOF NO ONE cmd ..." >> $LOGFILE  


$REDISCLI SLAVEOF NO ONE >> $LOGFILE 2>&1 


$  vim /etc/keepalived/scripts/redis_backup.sh


#!/bin/bash  


   


REDISCLI="/opt/redis/bin/redis-cli" 


LOGFILE="/var/log/keepalived-redis-state.log" 


   


echo "[backup]" >> $LOGFILE  


date >> $LOGFILE  


echo "Being slave...." >> $LOGFILE 2>&1  


   


sleep 15 #延迟15秒待数据被对方同步完成之后再切换主从角色  


echo "Run SLAVEOF cmd ..." >> $LOGFILE  


$REDISCLI SLAVEOF 192.168.0.2 6379 >> $LOGFILE  2>&1 


接着,在Redis Slave上创建notity_master与notify_backup脚本:


$  vim /etc/keepalived/scripts/redis_master.sh


#!/bin/bash  


   


REDISCLI="/opt/redis/bin/redis-cli" 


LOGFILE="/var/log/keepalived-redis-state.log" 


    


echo "[master]" >> $LOGFILE  


date >> $LOGFILE  


echo "Being master...." >> $LOGFILE 2>&1  


   


echo "Run SLAVEOF cmd ..." >> $LOGFILE  


$REDISCLI SLAVEOF 192.168.0.1 6379 >> $LOGFILE  2>&1  


sleep 10 #延迟10秒以后待数据同步完成后再取消同步状态  


   


echo "Run SLAVEOF NO ONE cmd ..." >> $LOGFILE  


$REDISCLI SLAVEOF NO ONE >> $LOGFILE 2>&1 


$  vim /etc/keepalived/scripts/redis_backup.sh


#!/bin/bash  


   


REDISCLI="/opt/redis/bin/redis-cli" 


LOGFILE="/var/log/keepalived-redis-state.log" 


  


echo "[backup]" >> $LOGFILE  


date >> $LOGFILE  


echo "Being slave...." >> $LOGFILE 2>&1  


    


sleep 15 #延迟15秒待数据被对方同步完成之后再切换主从角色  


echo "Run SLAVEOF cmd ..." >> $LOGFILE  


$REDISCLI SLAVEOF 192.168.0.1 6379 >> $LOGFILE  2>&1 


然后在Master与Slave创建如下相同的脚本:

$  vim /etc/keepalived/scripts/redis_fault.sh


#!/bin/bash  


   


LOGFILE=/var/log/keepalived-redis-state.log  


    


echo "[fault]" >> $LOGFILE  


date >> $LOGFILE 


$  vim /etc/keepalived/scripts/redis_stop.sh


#!/bin/bash  


    


LOGFILE=/var/log/keepalived-redis-state.log  


   


echo "[stop]" >> $LOGFILE  


date >> $LOGFILE 


给脚本都加上可执行权限:

$  chmod +x /etc/keepalived/scripts/*.sh


脚本创建完成以后,我们开始按照如下流程进行测试:

1.启动Master上的Redis

$  /etc/init.d/redis start


2.启动Slave上的Redis

$  /etc/init.d/redis start


3.启动Master上的Keepalived

$  /etc/init.d/keepalived start


4.启动Slave上的Keepalived

$  /etc/init.d/keepalived start


5.尝试通过VIP连接Redis:

$ redis-cli -h 192.168.0.253 INFO


连接成功,Slave也连接上来了。

role:master

slave0:192.168.0.2,6379,online


6.尝试插入一些数据:

$ redis-cli -h 192.168.0.253 SET Hello Redis

OK


从VIP读取数据

$ redis-cli -h 192.168.0.253 GET Hello

"Redis"


从Master读取数据

$ redis-cli -h 192.168.0.1 GET Hello

"Redis"


从Slave读取数据

$ redis-cli -h 192.168.0.2 GET Hello

"Redis"


下面,模拟故障产生:

将Master上的Redis进程杀死:

$  killall -9 redis-server


查看Master上的Keepalived日志

$ tail -f /var/log/keepalived-redis-state.log

[fault]

Thu Sep 27 08:29:01 CST 2012


同时Slave上的日志显示:

$ tail -f /var/log/keepalived-redis-state.log

[master]

Fri Sep 28 14:14:09 CST 2012

Being master....

Run SLAVEOF cmd ...

OK

Run SLAVEOF NO ONE cmd ...

OK


然后我们可以发现,Slave已经接管服务,并且担任Master的角色了。

$ redis-cli -h 192.168.0.253 INFO

$ redis-cli -h 192.168.0.2 INFO

role:master


然后我们恢复Master的Redis进程

$  /etc/init.d/redis start


查看Master上的Keepalived日志

$ tail -f /var/log/keepalived-redis-state.log

[master]

Thu Sep 27 08:31:33 CST 2012

Being master....

Run SLAVEOF cmd ...

OK

Run SLAVEOF NO ONE cmd ...

OK


同时Slave上的日志显示:

$ tail -f /var/log/keepalived-redis-state.log

[backup]

Fri Sep 28 14:16:37 CST 2012

Being slave....

Run SLAVEOF cmd ...

OK


可以发现目前的Master已经再次恢复了Master的角色,故障切换以及自动恢复都成功了。