Redis + Keepalived实现Redis的HA：

Redis + Keepalived实现Redis的HA：

环境介绍：
OS：CentOS 6.5
192.168.1.41    redis1      master
192.168.1.42    redis2      slave
VIP: 192.168.1.40

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.

1：在Master和Slave上安装、启动Redis
[root@redis1 ~]# cd /opt
[root@redis1 ~]# wget http://download.redis.io/releases/redis-2.8.12.tar.gz
[root@redis1 ~]# tar -zxvf redis-2.8.12.tar.gz
[root@redis1 ~]# cd redis-2.8.12
[root@redis1 ~]# make

如有编译报错，可以加上参数编译 make CFLAGS="-march=i686"

启动并运行redis：
[root@redis1 ~]# /opt/redis-2.8.12/src/redis-server &
[1] 1946
[root@redis1 ~]# [1946] 21 Jun 09:14:12.312 # Warning: no config file specified, using the default config. In order to specify a config file use /opt/redis-2.8.12/src/redis-server /path/to/redis.conf
[1946] 21 Jun 09:14:12.313 * Increased maximum number of open files to 10032 (it was originally set to 1024).
                _._                                                  
           _.-``__ ''-._                                             
      _.-``    `.  `_.  ''-._           Redis 2.8.12 (00000000/0) 64 bit
  .-`` .-```.  ```\/    _.,_ ''-._                                   
 (    '      ,       .-`  | `,    )     Running in stand alone mode
 |`-._`-...-` __...-.``-._|'` _.-'|     Port: 6379
 |    `-._   `._    /     _.-'    |     PID: 1946
  `-._    `-._  `-./  _.-'    _.-'                                   
 |`-._`-._    `-.__.-'    _.-'_.-'|                                  
 |    `-._`-._        _.-'_.-'    |           http://redis.io        
  `-._    `-._`-.__.-'_.-'    _.-'                                   
 |`-._`-._    `-.__.-'    _.-'_.-'|                                  
 |    `-._`-._        _.-'_.-'    |                                  
  `-._    `-._`-.__.-'_.-'    _.-'                                   
      `-._    `-.__.-'    _.-'                                       
          `-._        _.-'                                           
              `-.__.-'                                               
[1946] 21 Jun 09:14:12.318 # Server started, Redis version 2.8.12
[1946] 21 Jun 09:14:12.318 # WARNING overcommit_memory is set to 0! Background save may fail under low memory condition. To fix this issue add 'vm.overcommit_memory = 1' to /etc/sysctl.conf and then reboot or run the command 'sysctl vm.overcommit_memory=1' for this to take effect.
[1946] 21 Jun 09:14:12.318 * The server is now ready to accept connections on port 6379

打开另外一个终端运行redis客户端：
[root@redis1 ~]# /opt/redis-2.8.12/src/redis-cli 
127.0.0.1:6379> set name zhang
OK
127.0.0.1:6379> get name
"zhang"

2：安装配置keepalived
在master、slave安装keepalived：
[root@redis1 ~]# yum -y install keepalived

在Master上创建如下配置文件：
[root@redis1 ~]# vi /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 eth1                                                                               ###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 { 
             192.168.1.40                                                                         ###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Slave上创建如下配置文件：
vi /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 eth1                              ###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 { 
             192.168.1.40                           ###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
vi /etc/keepalived/scripts/redis_check.sh
#!/bin/bash
 ALIVE=`/opt/redis-2.8.12/src/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：
vi /etc/keepalived/scripts/redis_master.sh
#!/bin/bash
REDISCLI="/opt/redis-2.8.12/src/redis-cli"
LOGFILE="/opt/redis-2.8.12/log/keepalived-redis-state.log"
 
echo "[master]" >> $LOGFILE
date >> $LOGFILE
echo "Being master...." >> $LOGFILE 2>&1
 
echo "Run SLAVEOF cmd ..." >> $LOGFILE
$REDISCLI SLAVEOF 192.168.1.42 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


vi /etc/keepalived/scripts/redis_backup.sh
#!/bin/bash
 
REDISCLI="/opt/redis-2.8.12/src/redis-cli"
LOGFILE="/opt/redis-2.8.12/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 192.168.1.42 6379 >> $LOGFILE  2>&1

接着，在Redis Slave上创建notity_master与notify_backup脚本：
vi /etc/keepalived/scripts/redis_master.sh
#!/bin/bash
REDISCLI="/opt/redis-2.8.12/src/redis-cli"
LOGFILE="/opt/redis-2.8.12/log/keepalived-redis-state.log"
 
echo "[master]" >> $LOGFILE
date >> $LOGFILE
echo "Being master...." >> $LOGFILE 2>&1
 
echo "Run SLAVEOF cmd ..." >> $LOGFILE
$REDISCLI SLAVEOF 192.168.1.41 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


vi /etc/keepalived/scripts/redis_backup.sh
#!/bin/bash
 
REDISCLI="/opt/redis-2.8.12/src/redis-cli"
LOGFILE="/opt/redis-2.8.12/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 192.168.1.41 6379 >> $LOGFILE  2>&1

然后在Master与Slave创建如下相同的脚本：
vi /etc/keepalived/scripts/redis_fault.sh
#!/bin/bash
 
LOGFILE=/opt/redis-2.8.12/log/keepalived-redis-state.log
 
echo "[fault]" >> $LOGFILE
date >> $LOGFILE

vi /etc/keepalived/scripts/redis_stop.sh
#!/bin/bash
 LOGFILE=/opt/redis-2.8.12/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

1.启动Master上的Redis
[root@redis1 log]# /opt/redis-2.8.12/src/redis-server &

2.启动Slave上的Redis

[root@redis2 log]# /opt/redis-2.8.12/src/redis-server &

3.启动Master上的Keepalived

[root@redis1 log]# /etc/init.d/keepalived start

4.启动Slave上的Keepalived

[root@redis2 log]# /etc/init.d/keepalived start

5.尝试通过VIP连接Redis:
/opt/redis-2.8.12/src/redis-cli -h 192.168.1.40 INFO
连接成功，Slave也连接上来了。
# Replication
role:master
connected_slaves:1
slave0:ip=192.168.1.42,port=6379,state=online,offset=156,lag=1

6.尝试插入一些数据：
/opt/redis-2.8.12/src/redis-cli -h 192.168.1.40 SET Hello Redis
OK

从VIP读取数据
/opt/redis-2.8.12/src/redis-cli -h 192.168.1.40 GET Hello
"Redis"

从Master读取数据
/opt/redis-2.8.12/src/redis-cli -h 192.168.1.41 GET Hello
"Redis"

从Slave读取数据
/opt/redis-2.8.12/src/redis-cli -h 192.168.1.42 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 /opt/redis-2.8.12/log/keepalived-redis-state.log
[fault]
Thu Sep 27 08:29:01 CST 2012

同时Slave上的日志显示：
tail -80 /opt/redis-2.8.12/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

然后可以发现，Slave已经接管服务，并且担任Master的角色了。

/opt/redis-2.8.12/src/redis-cli -h 192.168.1.40 INFO
/opt/redis-2.8.12/src/redis-cli -h 192.168.1.42 INFO
role:master

然后恢复Master的Redis进程
/opt/redis-2.8.12/src/redis-server &

查看Master上的Keepalived日志
tail -80 /opt/redis-2.8.12/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 -80 /opt/redis-2.8.12/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。

参考文档：

http://blog.csdn.net/huwei2003/article/details/41894197