Redis主从架构持久化存在一个问题，即前次测试的结论，持久化需要配置在主实例上才能跨越实例保证数据不丢失，这样以来主实例在持久化数据到硬 盘的过程中，势必会造成磁盘的I/O等待，经过实际测试，这个持久化写硬盘的过程给应用程序带来的影响无法忍受；因而在大多数场景下，会考虑把持久化配置 在从实例上，当主实例宕机后，通过手动或者自动的方式将从实例提升为主实例，继续提供服务！当主实例恢复后，先从原从实例上同步数据，同步完成后再恢复到 原始的主从状态！要实现这种的要求，需要有keepalive的配合，一方面keepalive提供了VIP，可以避免修改应用程序连接，同时redis 实例的配置文件监听部分也需要修改为全网监听；另一方面keepalive定时调度脚本来监控主从实例的状态，根据具体情况进行切换！本文将重点介绍下使 用keepalive实现redis主从自动failover！
环境介绍
操作系统版本均为：rhel5.4 64bit
redis版本：2.6.4
redis实例端口均为：6379
redis实例密码均为：123
VIP：192.168.1.120
主实例为server11(192.168.1.112)
从实例为server12(192.168.1.113，开启快照持久化)
一：安装keepalive软件,server11安装完成后直接scp至server12上即可
[root@server11 ~]# wget http://keepalived.org/software/keepalived-1.1.19.tar.gz
[root@server11 ~]# tar -zxvf ../tarbag/keepalived-1.1.19.tar.gz
[root@server11 ~]# cd keepalived-1.1.19/
[root@server11 ~]# ./configure --prefix=/usr/local/keepalived && make && make install
二：配置主节点server11配置文件
[root@server11 ~]# cat /usr/local/keepalived/etc/keepalived/keepalived.conf
! Configuration File for keepalived global_defs {
router_id LVS_DEVEL
} vrrp_script Monitor_redis {
script "/usr/local/scripts/redis_monitor.sh"
interval 2
weight 2
} vrrp_instance VI_1{
state MASTER
interface eth0
virtual_router_id 51
mcast_src_ip 192.168.1.112
priority 100
advert_int 1
authentication {
auth_type PASS
auth_pass password_123
}
track_script {
Monitor_redis
}
virtual_ipaddress {
192.168.1.120
}
notify_fault /usr/local/scripts/redis_fault.sh
notify_stop /usr/local/scripts/redis_stop.sh }
三：配置从节点server12配置文件
[root@server12 ~]# cat /usr/local/keepalived/etc/keepalived/keepalived.conf
! Configuration File for keepalived global_defs {
router_id LVS_DEVEL
} vrrp_script Monitor_redis {
script "/usr/local/scripts/redis_monitor.sh"
interval 2
weight 2
} vrrp_instance VI_1{
state BACKUP
interface eth0
virtual_router_id 51
mcast_src_ip 192.168.1.113
priority 99
advert_int 1
authentication {
auth_type PASS
auth_pass password_123
}
track_script {
Monitor_redis
}
virtual_ipaddress {
192.168.1.120
}
notify_master /usr/local/scripts/redis_master.sh
notify_backup /usr/local/scripts/redis_backup.sh
notify_fault /usr/local/scripts/redis_fault.sh
notify_stop /usr/local/scripts/redis_stop.sh }
四：准备相关的脚本，主从实例上都需要存在这些脚本，同时注意脚本需要由可执行权限
[root@server11 ~]# cat /usr/local/scripts/redis_monitor.sh
#!/bin/bash
ALIVE=$(/usr/local/redis2/bin/redis-cli -h 192.168.1.112 -p 6379 -a 123 PING) if [ "$ALIVE" == "PONG" ]; then
echo $ALIVE
exit 0
else
echo $ALIVE
killall -9 keepalived
service network restart
exit 1
fi [root@server11 ~]# sh /usr/local/scripts/redis_monitor.sh
PONG [root@server11 ~]# cat /usr/local/scripts/redis_master.sh
#!/bin/bash
REDISCLI="/usr/local/redis2/bin/redis-cli -h 192.168.1.112 -p 6379 -a 123"
LOGFILE="/usr/local/redis2/var/keepalived-redis-state.log" echo "[master]" >> $LOGFILE
date >> $LOGFILE
echo "Being master...." >> $LOGFILE 2>&1
echo "Run SLAVEOF cmd ..." >> $LOGFILE
$REDISCLI SLAVEOF 192.168.1.113 6379 >> $LOGFILE 2>&1
sleep 10
echo "Run SLAVEOF NO ONE cmd ..." >> $LOGFILE
$REDISCLI SLAVEOF NO ONE >> $LOGFILE 2>&1 [root@server11 ~]# cat /usr/local/scripts/redis_backup.sh
#!/bin/bash
REDISCLI="/usr/local/redis2/bin/redis-cli -h 192.168.1.112 -p 6379 -a 123"
LOGFILE="/usr/local/redis2/var/keepalived-redis-state.log" echo "[backup]" >> $LOGFILE
date >> $LOGFILE
echo "Being slave...." >> $LOGFILE 2>&1
sleep 15
echo "Run SLAVEOF cmd ..." >> $LOGFILE
$REDISCLI SLAVEOF 192.168.1.113 6379 >> $LOGFILE 2>&1 [root@server11 ~]# cat /usr/local/scripts/redis_stop.sh
#!/bin/bash
LOGFILE="/usr/local/redis2/var/keepalived-redis-state.log"
echo "[stop]" >> $LOGFILE
date >> $LOGFILE
[root@server11 ~]# cat /usr/local/scripts/redis_fault.sh
#!/bin/bash
LOGFILE="/usr/local/redis2/var/keepalived-redis-state.log"
echo "[fault]" >> $LOGFILE
date >> $LOGFILE
五：主从实例分别启动keepalive进程，测试VIP是否正常(这里就要修改redis配置文件的监听地址为0.0.0.0)
[root@server11 ~]# /usr/local/keepalived/sbin/keepalived -D -f /usr/local/keepalived/etc/keepalived/keepalived.conf
[root@server11 ~]# tail -f /var/log/messages
Dec 12 09:25:49 server11 Keepalived_healthcheckers[7710]: Configuration is using : 5499 Bytes
Dec 12 09:25:49 server11 Keepalived_healthcheckers[7710]: Using LinkWatch kernel netlink reflector...
Dec 12 09:25:49 server11 Keepalived_vrrp[7712]: VRRP sockpool: [ifindex(2), proto(112), fd(12,13)]
Dec 12 09:25:49 server11 Keepalived_vrrp[7712]: VRRP_Script(Monitor_redis) succeeded
Dec 12 09:25:50 server11 Keepalived_vrrp[7712]: VRRP_Instance(VI_1{) Transition to MASTER STATE
Dec 12 09:25:51 server11 Keepalived_vrrp[7712]: VRRP_Instance(VI_1{) Entering MASTER STATE
Dec 12 09:25:51 server11 Keepalived_vrrp[7712]: VRRP_Instance(VI_1{) setting protocol VIPs.
Dec 12 09:25:51 server11 Keepalived_vrrp[7712]: VRRP_Instance(VI_1{) Sending gratuitous ARPs on eth0 for 192.168.1.120
Dec 12 09:25:51 server11 avahi-daemon[4519]: Registering new address record for 192.168.1.120 on eth0.
Dec 12 09:25:51 server11 Keepalived_healthcheckers[7710]: Netlink reflector reports IP 192.168.1.120 added
Dec 12 09:25:51 server11 Keepalived_vrrp[7712]: Netlink reflector reports IP 192.168.1.120 added
Dec 12 09:25:56 server11 Keepalived_vrrp[7712]: VRRP_Instance(VI_1{) Sending gratuitous ARPs on eth0 for 192.168.1.120 [root@server11 ~]# ip a |grep 192
inet 192.168.1.112/24 brd 192.168.1.255 scope global eth0
inet 192.168.1.120/32 scope global eth0 [root@server12 ~]# /usr/local/keepalived/sbin/keepalived -D -f /usr/local/keepalived/etc/keepalived/keepalived.conf
[root@server12 ~]# tail -f /var/log/messages
Dec 12 09:26:55 server12 Keepalived_healthcheckers[3106]: Configuration is using : 5595 Bytes
Dec 12 09:26:55 server12 Keepalived_vrrp[3108]: VRRP_Instance(VI_1{) Entering BACKUP STATE
Dec 12 09:26:55 server12 Keepalived_healthcheckers[3106]: Using LinkWatch kernel netlink reflector...
Dec 12 09:26:55 server12 Keepalived_vrrp[3108]: VRRP sockpool: [ifindex(2), proto(112), fd(12,13)]
Dec 12 09:26:55 server12 Keepalived_vrrp[3108]: VRRP_Script(Monitor_redis) succeeded [root@server11 ~]# /usr/local/redis2/bin/redis-cli -h 192.168.1.120 -a 123 info |grep -A 3 'Replication'
# Replication
role:master
connected_slaves:1
slave0:192.168.1.113,6379,online
六：主实例写入测试数据，该脚本原则上会写入25条测试数据，不过由于未优化redis默认并发数，会导致一些写入请求失败，最终功写入231839条测 试数据，占内存总大小为25M左右，写入过程中可以观察主从实例的持久化文件变化情况，主实例的持久化文件维持在30k，从实例的则不断的扩展！
[root@server11 ~]# cat test.sh
#!/bin/bash
REDISCLI="/usr/local/redis2/bin/redis-cli -h 192.168.1.120 -a 123 -n 1 SET"
ID=1
while(($ID<))
do
INSTANCE_NAME="i-2-$ID-VM"
UUID=`cat /proc/sys/kernel/random/uuid`
PRIVATE_IP_ADDRESS=10.`echo "$RANDOM % 255 + 1" | bc`.`echo "$RANDOM % 255 + 1" | bc`.`echo "$RANDOM % 255 + 1" | bc`\
CREATED=`date "+%Y-%m-%d %H:%M:%S"`
$REDISCLI vm_instance:$ID:instance_name "$INSTANCE_NAME"
$REDISCLI vm_instance:$ID:uuid "$UUID"
$REDISCLI vm_instance:$ID:private_ip_address "$PRIVATE_IP_ADDRESS"
$REDISCLI vm_instance:$ID:created "$CREATED"
$REDISCLI vm_instance:$INSTANCE_NAME:id "$ID"
ID=$(($ID+1))
done [root@server11 ~]# sh test.sh
[root@server11 redis2]# /usr/local/redis2/bin/redis-cli -h 192.168.1.120 -a 123 info |egrep 'used_memory_peak_human|db1:keys'
used_memory_peak_human:24.98M
db1:keys=231839,expires=0
七：模拟主实例故障，观察日志输出，验证从实例是否能成功接管VIP，同时将实例变成读写模式
[root@server11 ~]# killall -9 redis-server
[root@server11 ~]# ip a |grep 192
inet 192.168.1.112/24 brd 192.168.1.255 scope global eth0 [root@server11 ~]# ps -ef |grep redis
root 15886 6458 0 09:49 pts/0 00:00:00 grep redis
[root@server11 ~]# ps -ef |grep keep
root 16029 6458 0 09:49 pts/0 00:00:00 grep keep [root@server12 ~]# tail -f /usr/local/redis2/var/keepalived-redis-state.log
[master]
Wed Dec 12 09:48:52 CST 2012
Being master....
Run SLAVEOF cmd ...
OK Already connected to specified master
Run SLAVEOF NO ONE cmd ...
OK [root@server12 ~]# tail -f /var/log/messages
Dec 12 09:48:51 server12 Keepalived_vrrp[3108]: VRRP_Instance(VI_1{) Transition to MASTER STATE
Dec 12 09:48:52 server12 Keepalived_vrrp[3108]: VRRP_Instance(VI_1{) Entering MASTER STATE
Dec 12 09:48:52 server12 Keepalived_vrrp[3108]: VRRP_Instance(VI_1{) setting protocol VIPs.
Dec 12 09:48:52 server12 Keepalived_vrrp[3108]: VRRP_Instance(VI_1{) Sending gratuitous ARPs on eth0 for 192.168.1.120
Dec 12 09:48:52 server12 Keepalived_vrrp[3108]: Netlink reflector reports IP 192.168.1.120 added
Dec 12 09:48:52 server12 avahi-daemon[2921]: Registering new address record for 192.168.1.120 on eth0.
Dec 12 09:48:52 server12 Keepalived_healthcheckers[3106]: Netlink reflector reports IP 192.168.1.120 added
Dec 12 09:48:57 server12 Keepalived_vrrp[3108]: VRRP_Instance(VI_1{) Sending gratuitous ARPs on eth0 for 192.168.1.120 [root@server12 ~]# ip a |grep 192
inet 192.168.1.113/24 brd 192.168.1.255 scope global eth0
inet 192.168.1.120/32 scope global eth0 [root@server12 ~]# /usr/local/redis2/bin/redis-cli -h 192.168.1.120 -a 123 info |grep -A 3 'Replication'
# Replication
role:master
connected_slaves:0
[root@server12 ~]# sh test.sh
[root@server12 ~]# /usr/local/redis2/bin/redis-cli -h 192.168.1.120 -a 123 info |egrep 'used_memory_peak_human|db1:keys'
used_memory_peak_human:26.78M
db1:keys=249925,expires=0
九:主实例角色的恢复过程，使用shell脚本自动恢复
[root@server11 ~]# ssh-keygen
[root@server11 ~]# cd .ssh/
[root@server11 .ssh]# ssh-copy-id -i id_rsa.pub root@192.168.1.113
[root@server11 ~]# cat /usr/local/scripts/recover_mastart.sh
#!/bin/sh
ALIVE=$(/usr/local/redis2/bin/redis-cli -h 192.168.1.113 -p 6379 -a 123 PING)
MDB=/usr/local/redis2/master_dump.rdb
SDB=/usr/local/redis2/slave_dump.rdb if [ "$ALIVE" == "PONG" ]; then
echo $ALIVE
scp root@192.168.1.113:$SDB $MDB
else
echo $ALIVE
exit 1
fi /usr/local/redis2/bin/redis-server /usr/local/redis2/etc/redis.conf
/usr/local/keepalived/sbin/keepalived -D -f /usr/local/keepalived/etc/keepalived/keepalived.conf [root@server11 ~]# chmod +x /usr/local/scripts/recover_mastart.sh
[root@server11 ~]# sh /usr/local/scripts/recover_mastart.sh
十：验证数据完整性和主从角色恢复情况
[root@server11 ~]# /usr/local/redis2/bin/redis-cli -h 192.168.1.120 -a 123 info |egrep 'used_memory_peak_human|db1:keys'
used_memory_peak_human:26.78M
db1:keys=249925,expires=0 [root@server11 ~]# /usr/local/redis2/bin/redis-cli -h 192.168.1.120 -a 123 info |grep -A 3 'Replication'
# Replication
role:master
connected_slaves:1
slave0:192.168.1.113,6379,online [root@server12 ~]# /usr/local/redis2/bin/redis-cli -h 192.168.1.113 -a 123 info |grep -A 3 'Replication'
# Replication
role:slave
master_host:192.168.1.112
master_port:6379 [root@server12 ~]# /usr/local/redis2/bin/redis-cli -h 192.168.1.120 -a 123 info |egrep 'used_memory_peak_human|db1:keys'
used_memory_peak_human:26.78M
db1:keys=249925,expires=0 主实例keepalive日志：
[root@server11 ~]# tail -f /var/log/messages
Dec 12 10:08:13 server11 Keepalived_vrrp[20231]: VRRP sockpool: [ifindex(2), proto(112), fd(11,12)]
Dec 12 10:08:13 server11 Keepalived_vrrp[20231]: VRRP_Script(Monitor_redis) succeeded
Dec 12 10:08:13 server11 Keepalived_vrrp[20231]: VRRP_Instance(VI_1{) Transition to MASTER STATE
Dec 12 10:08:13 server11 Keepalived_vrrp[20231]: VRRP_Instance(VI_1{) Received higher prio advert
Dec 12 10:08:13 server11 Keepalived_vrrp[20231]: VRRP_Instance(VI_1{) Entering BACKUP STATE
Dec 12 10:08:15 server11 Keepalived_vrrp[20231]: VRRP_Instance(VI_1{) forcing a new MASTER election
Dec 12 10:08:16 server11 Keepalived_vrrp[20231]: VRRP_Instance(VI_1{) Transition to MASTER STATE
Dec 12 10:08:17 server11 Keepalived_vrrp[20231]: VRRP_Instance(VI_1{) Entering MASTER STATE
Dec 12 10:08:17 server11 Keepalived_vrrp[20231]: VRRP_Instance(VI_1{) setting protocol VIPs.
Dec 12 10:08:17 server11 Keepalived_healthcheckers[20230]: Netlink reflector reports IP 192.168.1.120 added
Dec 12 10:08:17 server11 Keepalived_vrrp[20231]: VRRP_Instance(VI_1{) Sending gratuitous ARPs on eth0 for 192.168.1.120
Dec 12 10:08:17 server11 Keepalived_vrrp[20231]: Netlink reflector reports IP 192.168.1.120 added
Dec 12 10:08:17 server11 avahi-daemon[4519]: Registering new address record for 192.168.1.120 on eth0. [root@server11 ~]# ip a |grep 192
inet 192.168.1.112/24 brd 192.168.1.255 scope global eth0
inet 192.168.1.120/32 scope global eth0 从实例keepalive日志：
[root@server12 ~]# tail -f /var/log/messages
Dec 12 09:56:01 server12 last message repeated 4 times
Dec 12 10:08:13 server12 Keepalived_vrrp[3108]: VRRP_Instance(VI_1{) Received lower prio advert, forcing new election
Dec 12 10:08:13 server12 Keepalived_vrrp[3108]: VRRP_Instance(VI_1{) Sending gratuitous ARPs on eth0 for 192.168.1.120
Dec 12 10:08:15 server12 Keepalived_vrrp[3108]: VRRP_Instance(VI_1{) Received higher prio advert
Dec 12 10:08:15 server12 Keepalived_vrrp[3108]: VRRP_Instance(VI_1{) Entering BACKUP STATE
Dec 12 10:08:15 server12 Keepalived_vrrp[3108]: VRRP_Instance(VI_1{) removing protocol VIPs.
Dec 12 10:08:15 server12 Keepalived_healthcheckers[3106]: Netlink reflector reports IP 192.168.1.120 removed
Dec 12 10:08:15 server12 Keepalived_vrrp[3108]: Netlink reflector reports IP 192.168.1.120 removed
Dec 12 10:08:15 server12 avahi-daemon[2921]: Withdrawing address record for 192.168.1.120 on eth0. 从实例角色转换日志：
[root@server12 ~]# tail -f /usr/local/redis2/var/keepalived-redis-state.log
[backup]
Wed Dec 12 10:08:15 CST 2012
Being slave....
Run SLAVEOF cmd ...
OK