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:
2.启动Slave上的Redis
4.启动Slave上的Keepalived
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”
从Master读取数据
“Redis”
下面,模拟故障产生:
将Master上的Redis进程杀死:
[fault]
Thu Sep 27 08:29:01 CST 2012
同时Slave上的日志显示:
查看Master上的Keepalived日志
[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。