redis+Keepalived实现Redis高可用性

转载自：http://heylinux.com/archives/1942.html

目前，Redis还没有一个类似于MySQL Proxy或Oracle RAC的官方HA方案。

Redis作者有一个名为Redis Sentinel的计划(http://redis.io/topics/sentinel)，据称将会有监控，报警和自动故障转移三大功能，非常不错。但可惜的是短期内恐怕还不能开发完成。

官方的redis集群方案还在开发阶段，3.0.0beta版本已经支持redis cluster功能。

因此，如何在出现故障时自动转移是一个需要解决的问题。

通过对网上一些资料的搜索，有建议采用HAProxy或Keepalived来实现的，事实上如果是做Failover而非负载均衡的话，Keepalived的效率肯定是超过HAProxy的，所以我决定采用Keepalived的方案。

环境介绍：

Master: 10.6.1.143

Slave: 10.6.1.144

Virtural IP Address (VIP): 10.6.1.200

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。

下面，是具体的实施步骤：

在Master和Slave上安装Keepalived

$ sudo apt-get install keepalived

首先，在Master上创建如下配置文件：

$ sudo 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 {
10.6.1.200                         ###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：

$ sudo 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 {
10.6.1.200                         ###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

$ sudo mkdir /etc/keepalived/scripts
$ sudo vim /etc/keepalived/scripts/redis_check.sh
#!/bin/bash

ALIVE=`/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：

1.创建redis_master.sh

$ sudo 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 10.6.1.144 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

2.创建redis_backup.sh文件

$ sudo 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 10.6.1.144 6379 >> $LOGFILE  2>&1

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

1.创建redis_master.sh

$ sudo 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 10.6.1.143 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

2.创建redis_backup.sh

$ sudo 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 10.6.1.143 6379 >> $LOGFILE  2>&1

然后在Master与Slave创建如下相同的脚本：

1.创建redis_fault.sh

$ sudo vim /etc/keepalived/scripts/redis_fault.sh
#!/bin/bash

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

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

2.创建redis_stop.sh

$ sudo 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：

sudochmod+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 sudo /etc/init.d/redis start

2.启动Slave上的Redis

sudo/etc/init.d/redisstart3.启动Master上的Keepalived sudo /etc/init.d/keepalived start

4.启动Slave上的Keepalived

sudo/etc/init.d/keepalivedstart5.尝试通过VIP连接Redis: redis-cli -h 10.6.1.200 INFO

连接成功，Slave也连接上来了。

role:master

slave0:10.6.1.144,6379,online

6.尝试插入一些数据：

redis−cli−h10.6.1.200SETHelloRedisOK从VIP读取数据 redis-cli -h 10.6.1.200 GET Hello

“Redis”

从Master读取数据

redis−cli−h10.6.1.143GETHello“Redis”从Slave读取数据 redis-cli -h 10.6.1.144 GET Hello

“Redis”

下面，模拟故障产生：

将Master上的Redis进程杀死：

sudokillall−9redis−server查看Master上的Keepalived日志 tailf /var/log/keepalived-redis-state.log

[fault]

Thu Sep 27 08:29:01 CST 2012

同时Slave上的日志显示：

tailf/var/log/keepalived−redis−state.log[master]FriSep2814:14:09CST2012Beingmaster….RunSLAVEOFcmd…OKRunSLAVEOFNOONEcmd…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 10.6.1.200 INFO

redis−cli−h10.6.1.144INFOrole:master然后我们恢复Master的Redis进程 sudo /etc/init.d/redis start

查看Master上的Keepalived日志

tailf/var/log/keepalived−redis−state.log[master]ThuSep2708:31:33CST2012Beingmaster….RunSLAVEOFcmd…OKRunSLAVEOFNOONEcmd…OK同时Slave上的日志显示： tailf /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。