debian6下redis+keepalived故障自动切换

环境介绍：

Master: 1192.168.2.140

Slave:
1192.168.2.141

Virtural IP Address (VIP): 192.168.200.16

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.安装keepalived

root@dead:/usr/local/src# wget http://www.keepalived.org/software/keepalived-1.2.13.tar.gz

root@dead:/usr/local/src# tar -xzvf keepalived-1.2.13.tar.gz

root@dead:/usr/local/src# mv keepalived-1.2.13 /usr/local/

root@dead:/usr/local/keepalived-1.2.13# ./configure

注意：执行完configure操作后，可能会出现如下错误：

configure: error:
  !!! OpenSSL is not properly installed on your system. !!!
  !!! Can not include OpenSSL headers files.            !!!

若出现，执行如下操作：

root@dead:/usr/local/keepalived-1.2.13# apt-get install libssl-dev

安装结束后，再次执行configure操作，正常执行！

root@dead:/usr/local/keepalived-1.2.13# make && make install

在Master和Slave上安装Keepalived结束！

2.编辑Master和Slave的keepalived.conf文件

root@dead:/usr/local/etc/keepalived# vi keepalived.conf

master编辑如下，若不存在则增加，存在则修改，多余不用碰：

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 1111            ###密码 
        } 
        track_script { 
                chk_redis                       ###执行上面定义的chk_redis
        } 
        virtual_ipaddress { 
             192.168.200.16                         ###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 
}

slave编辑如下，若不存在则增加，存在则修改，多余不用碰：

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 { 
             192.168.200.16                        ###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

root@dead:/etc# mkdir /etc/keepalived
root@dead:/etc# mkdir /etc/keepalived/scripts

root@dead:/etc# vi /etc/keepalived/scripts/redis_check.sh

增加如下：

#!/bin/bash

ALIVE=`/usr/local/redis-2.8.13/src/redis-cli -p 12002 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：

root@dead:/etc# vi  /etc/keepalived/scripts/redis_master.sh

#!/bin/bash

REDISCLI="/usr/local/redis-2.8.13/src/redis-cli -p 12002"
LOGFILE="/var/log/keepalived-redis-state.log"

echo "[master]" >> $LOGFILE
date >> $LOGFILE
echo "Being master...." >> $LOGFILE 2>&1

echo "Run SL***EOF cmd ..." >> $LOGFILE
$REDISCLI SL***EOF 192.168.2.141 12002 >> $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 SL***EOF NO ONE cmd ..." >> $LOGFILE
$REDISCLI SL***EOF NO ONE >> $LOGFILE 2>&1

</pre><pre name="code" class="html">

vi /etc/keepalived/scripts/redis_backup.sh

#!/bin/bash

REDISCLI="/usr/local/redis-2.8.13/src/redis-cli -p 12002"
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 SL***EOF cmd ..." >> $LOGFILE
$REDISCLI SL***EOF 192.168.2.141 12002 >> $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="/usr/local/redis-2.8.13/src/redis-cli -p 12002"
LOGFILE="/var/log/keepalived-redis-state.log"

echo "[master]" >> $LOGFILE
date >> $LOGFILE
echo "Being master...." >> $LOGFILE 2>&1

echo "Run SL***EOF cmd ..." >> $LOGFILE
$REDISCLI SL***EOF 192.168.2.140 12002 >> $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 SL***EOF NO ONE cmd ..." >> $LOGFILE
$REDISCLI SL***EOF NO ONE >> $LOGFILE 2>&1

vi /etc/keepalived/scripts/redis_backup.sh

#!/bin/bash

REDISCLI="/usr/local/redis-2.8.13/src/redis-cli -p 12002"
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 SL***EOF cmd ..." >> $LOGFILE
$REDISCLI SL***EOF 192.168.2.140 12002 >> $LOGFILE  2>&1

然后在Master与Slave创建如下相同的脚本：

/etc/keepalived/scripts/redis_fault.sh

#!/bin/bash

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

echo "[fault]" >> $LOGFILE
date >> $LOGFILE

vi /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：

$ sudo 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

$ /usr/local/redis-2.8.13/src/redis-server /usr/local/redis-2.8.13/redis.conf

2.启动Slave上的Redis

$ /usr/local/redis-2.8.13/src/redis-server /usr/local/redis-2.8.13/redis.conf

3.启动Master上的Keepalived

$ root@dead:/usr/local/etc/keepalived# keepalived

4.启动Slave上的Keepalived

$
usr/local/etc/keepalived# keepalived

5.尝试通过VIP连接Redis:

$ /usr/local/redis-2.8.13/src/redis-cli -h 192.168.200.16 -p 12002 INFO

注意：在master上执行此操作时会报如下错误：

Could not connect to Redis at 192.168.200.16:12002: No route to host

采取措施1：（在master和slave中修改文件如下）

vi /etc/hosts

127.0.0.1   localhost

192.168.2.140  redis

192.168.2.141  redis-slave

执行依然出错！

采取措施2：

cp /usr/local/etc/keepalived/keepalived.conf /etc/keepalived/

执行操作成功！

连接成功，Slave也连接上来了。连接后，显示的部分内容如下：

# Replication
role:master
connected_slaves:1
slave0:ip=192.168.2.141,port=12002,state=online,offset=520,lag=0
master_repl_offset:520
repl_backlog_active:1
repl_backlog_size:1048576
repl_backlog_first_byte_offset:17
repl_backlog_histlen:504

6.尝试插入一些数据：

root@dead:/usr/local/etc/keepalived# /usr/local/redis-2.8.13/src/redis-cli -h 192.168.200.16 -p 12002
192.168.200.16:12002> set go gotodeath
OK
192.168.200.16:12002> get go
"gotodeath"
192.168.200.16:12002>

从VIP读取数据

192.168.200.16:12002> get go
"gotodeath"

从Master读取数据

root@dead:/usr/local/etc/keepalived# /usr/local/redis-2.8.13/src/redis-cli -p 12002
127.0.0.1:12002> get go
"gotodeath"
127.0.0.1:12002>

从Slave读取数据

root@gone:/usr/local/etc/keepalived# /usr/local/redis-2.8.13/src/redis-cli -p 12002
127.0.0.1:12002> get go
"gotodeath"
127.0.0.1:12002>

下面，模拟故障产生：

将Master上的Redis进程杀死：

$ sudo killall -9 redis-server
141日志如下：（）



140日志如下：



参考资料：http://heylinux.com/archives/1942.html