参考资料：
http://my.oschina.net/guol/blog/182491
http://www.voidcn.com/article/p-nqaaudex-gs.html
http://www.qixing318.com/article/by-keepalived-redis-double-machine.html
背景
目前，Redis集群的官方方案还处在开发测试中，未集成到稳定版中。且目前官方开发中的Redis Cluster提供的功能尚不完善（可参考官方网站或http://www.redisdoc.com/en/latest/topic/cluster-spec.html），在生产环境中不推荐使用。通过调研发现市面上要实现采用单一的IP来访问，大多采用keepalived实现redis的双机热备作为过渡方案。
环境部署
环境介绍：
Master: 192.168.1.218 redis，keepalived
Slave: 192.168.1.219 redis，keepalived
Virtural IP Address (VIP): 192.168.1.220
以下Master表示192.168.1.218这台主机，Slave表示192.168.1.219这台主机；master/slave表示keepalived/redis的role。(首字母大小写的区别)
设计思路：
通过keepalived的自定义脚本功能监控本机的redis服务状态，当监控脚本检测到redis服务出现异常时，则将本机的keepalived关闭，同时这会导致master/backup角色的变化，而keepalived在角色变化时也会触发一些机制执行相关脚本，这就为我们改变redis的master/slave状态提供了机会，这样做的目的是为了是redis的master/slave的数据保持一致。
在keepalived+redis的使用过程中有四种情况：
1 一种是keepalived挂了，同时redis也挂了，这样的话直接VIP飘走之后，是不需要进行redis数据同步的，因为redis挂了，你也无法去master上同步，不过会损失已经写在master上却还没同步到slave上面的这部分数据。
2 另一种是keepalived挂了，redis没挂，这时候VIP飘走后，redis的master/slave还是老的对应关系，如果不变化的话会把数据写入redis slave中，从而不会同步到master上去，这就要借助监控脚本反转redis的master/slave关系。这时候就要预留一点时间进行数据同步，然后反转master/slave。
3 还有一种是keepalived没挂，redis挂了，这时候根据监控脚本会检测到redis挂了，将本地的keepalived关闭，将虚拟IP漂移到另外一台服务器上。由另外一台备机承接redis业务。
4 随后一种是keepalived没挂，redis也没挂，什么都不用操作。
本文的实验环境四种情况都适合，第一种是不需要同步数据的，脚本会默认去同步数据，但是其实是不会成功的。脚本主要是用来处理第二和第三种情况的。
实施步骤：
——————-创建专用用户——————-
useradd -g develop redisadmin
echo ******|passwd –stdin redisadmin
说明：以下部署过程都是在root(或具备sudo权限的账号)账户下进行。
——————-安装配置redis——————-
在Master和Slave上进行如下操作：
1.下载redis源码
cd
wget http://download.redis.io/releases/redis-2.8.4.tar.gz
2.安装redis
tar -zxvf redis-2.8.4.tar.gz
cd redis-2.8.4
#reds的安装可以不用执行configure
make
#测试
make test
####在速度较慢的机器上执行make test可能出现下列错误，无影响
#*** [err]: Test replication partial resync: no backlog in tests/integration/replication-psync.tcl
3.配置redis
#创建redis主目录
mkdir -p /usr/local/redis/{bin,conf,logs}
#将可执行文件拷贝到相应的目录
find src/ ( -perm -0001 ) -type f -exec cp -a -R -p {} /usr/local/redis/bin ;
#创建redis启动脚本
vi /usr/local/redis/redis-start.sh
####以下是master上的配置，slave上的配置只需修改对应的IP地址。
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2RPATH=/usr/local/redis
3KPATH=/usr/local/keepalived
4REDISCLI=$RPATH/bin/redis-cli
5LOGFILE=$KPATH/logs/redis-state.log
6LOCALIP=192.168.1.218
7REMOTEIP=192.168.1.219
8
9$RPATH/bin/redis-server $RPATH/conf/redis.conf
10if [ "$?" == "0" ];then
11 echo "[INFO]`date +%F/%H:%M:%S` :$LOCALIP redis start successful." >> $LOGFILE
12else
13 echo "[ERROR]`date +%F/%H:%M:%S` :$LOCALIP redis start error." >> $LOGFILE
14fi
15
#创建redis关闭脚本
vi /usr/local/redis/redis-stop.sh
####以下为master上的配置，slave上的配置只需修改对应的IP地址。
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2RPATH=/usr/local/redis
3KPATH=/usr/local/keepalived
4LOGFILE=$KPATH/logs/redis-state.log
5LOCALIP=192.168.1.218
6REMOTEIP=192.168.219
7kill -9 `ps -ef|grep '/bin/redis-server'|grep -v grep|awk '{print $2}'`
8if [ "$?" == "0" ];then
9 echo "[INFO]`date +%F/%H:%M:%S` :$LOCALIP redis shutdown completed!" >> $LOGFILE
10else
11 echo "[INFO]`date +%F/%H:%M:%S` :$LOCALIP redis is not started." >> $LOGFILE
12fi
13
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cp -a -R -p redis.conf /usr/local/redis/conf/redis.conf
#修改redis.conf对应配置项：
vi /usr/local/redis/conf/redis.conf
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2daemonize yes
3pidfile /usr/local/redis/redis.pid
4#bind 192.168.1.218 #暂时注释，方便测试
5timeout 300
6loglevel verbose #实际生产环境可用notice，此处是为了详细查看各种输出细节
7logfile "/usr/local/redis/logs/redis.log"
8dir /usr/local/redis/
9appendonly yes
10
#修改redis的属主和权限
chmod -R 750 /usr/local/redis/
chown -R redisadmin:develop /usr/local/redis/
——————-安装配置keepalived——————-
1.下载keepalived最新源码包1.2.10
wget http://www.keepalived.org/software/keepalived-1.2.10.tar.gz
2.安装keepalived
需要先安装以下依赖包： make gcc libpopt-dev libnl-dev libcurl4-openssl-dev popt openssl
cd
tar zxvf keepalived-1.2.10.tar.gz
cd keepalived-1.2.10
注意：先按照下列出错解决版本修改后再执行后面步骤：
./configure –prefix=/usr/local/keepalived
make && make install
安装出错（在版本1.2.9上不会出错）：
解决办法：
vi ~/keepalived-1.2.10/keepalived/libipvs-2.6/libipvs.c
按照下图的方法修正（新增57行，注释82行）：
3.配置keepalived
cd /usr/local/keepalived
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#在Master:192.168.1.218上创建如下配置文件（可根据实际情况调整）：
vi /usr/local/keepalived/etc/keepalived/keepalived.conf
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3#global_defs {
4# notification_email {
5# }
6# notification_email_from Alexandre.Cassen@firewall.loc
7# router_id node3
8#}
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10vrrp_script chk_redis {
11 script "/usr/local/keepalived/etc/keepalived/scripts/redis_check.sh"
12#如果脚本执行结果非0，并且weight配置的值小于0，则优先级相应的减少;如果脚本执行结果为0，并且weight配置的值大于0，则优先级相应的增加;其他情况，维持原本prority的优先级。
13# weight -20
14 interval 10 #设置脚本执行的频率。10秒一次
15}
16
17vrrp_instance VI_1 {
18 state BACKUP #要设置恢复时不抢占，需要将主，从服务器的此项都设置成BACKUP,nopreempt才会生效。
19 #state MASTER
20 interface eth3
21 virtual_router_id 51
22 priority 100
23 nopreempt #设置不抢占。在priority值比较高的服务器上设置即可。priority值比较低的服务器启动时，发现值高的服务器为master，自动不抢占。
24 #advert_int的作用是巡检的次数。keepalived默认是在启动完成后3秒向state：MASTER切换。若此处设置成2，则是2*3=6秒后才开启切换。
25 advert_int 1
26 authentication {
27 auth_type PASS
28 auth_pass redis
29 }
30 virtual_ipaddress {
31 192.168.1.220
32 }
33 track_script {
34 chk_redis
35 }
36 notify_master /usr/local/keepalived/etc/keepalived/scripts/master.sh
37 notify_backup /usr/local/keepalived/etc/keepalived/scripts/backup.sh
38 notify_fault /usr/local/keepalived/etc/keepalived/scripts/fault.sh
39 notify_stop /usr/local/keepalived/etc/keepalived/scripts/stop.sh
40}
41
#在Slave:192.168.1.219上创建如下配置文件（可根据实际情况调整）：
vi /usr/local/keepalived/etc/keepalived/keepalived.conf
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4# notification_email {
5# }
6# notification_email_from Alexandre.Cassen@firewall.loc
7# router_id node3
8#}
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10vrrp_script chk_redis {
11 script "/usr/local/keepalived/etc/keepalived/scripts/redis_check.sh"
12#如果脚本执行结果非0，并且weight配置的值小于0，则优先级相应的减少;如果脚本执行结果为0，并且weight配置的值大于0，则优先级相应的增加;其他情况，维持原本prority的优先级。
13# weight -20
14 interval 10 #设置脚本执行的频率。10秒一次
15}
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17vrrp_instance VI_1 {
18 state BACKUP
19 interface eth5
20 garp_master_delay 10
21 virtual_router_id 51
22 priority 90
23 #nopreempt
24 #advert_int的作用是巡检的次数。keepalived默认是在启动完成后3秒向state：MASTER切换。若此处设置成2，则是2*3=6秒后才开启切换。
25 advert_int 1
26 authentication {
27 auth_type PASS
28 auth_pass redis
29 }
30 virtual_ipaddress {
31 192.168.1.220
32 }
33 track_script {
34 chk_redis
35 }
36 notify_master /usr/local/keepalived/etc/keepalived/scripts/master.sh #当keepalived切换成master时，会触发执行master.sh
37 notify_backup /usr/local/keepalived/etc/keepalived/scripts/backup.sh #当keepalived切换成slave时，会触发执行slave.sh
38 notify_fault /usr/local/keepalived/etc/keepalived/scripts/fault.sh #当keepalived出错时，会触发执行fault.sh
39 notify_stop /usr/local/keepalived/etc/keepalived/scripts/stop.sh #当keepalived停止时，会触发执行stop.sh
40}
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2KEEPALIVED_OPTIONS="-D -d -S 0"
3
#redhat6.0以下服务器修改/etc/syslog.conf,redhat6.0以上（包括6.0）服务器修改/etc/rsyslog.conf,新增以下内容：
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2local0.* /usr/local/keepalived/logs/keepalived.log
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#重启日志服务
service rsyslog restart
#将文件拷贝到相应的位置
cp -r * /
#在Master和Slave上创建监控Redis的相关脚本脚本，以下脚本都是master上的配置，slave上只需修改相应的IP地址。
mkdir /usr/local/keepalived/etc/keepalived/scripts
vi /usr/local/keepalived/etc/keepalived/scripts/redis_check.sh
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2KPATH=/usr/local/keepalived
3RPATH=/usr/local/redis
4REDISCLI=$RPATH/bin/redis-cli
5LOGFILE=$KPATH/logs/redis-state.log
6LOCALIP="192.168.1.218"
7REMOTEIP="192.168.1.219"
8PORT="6379"
9PID=$$
10
11ALIVE=`$REDISCLI PING`
12if [ "$ALIVE" == "PONG" ]; then
13 echo "[INFO]`date +'%Y-%m-%d:%H:%M:%S'` :$LOCALIP local redis is health." >> $LOGFILE
14 exit 0
15else
16 echo "[ERROR]`date +'%Y-%m-%d:%H:%M:%S'` :$LOCALIP local redis is not health." >> $LOGFILE
17 #当发现本地redis无法连接时，等待一秒后再进行一次检查。若恢复，则提示；若仍无法连接，则关闭本地keepalived,将虚拟ip漂移到另外一台服务器上。
18 sleep 1
19 ALIVE1=`$REDISCLI PING`
20 if [ "$ALIVE1" == "PONG" ];then
21 echo "[NOTICE]`date +'%Y-%m-%d:%H:%M:%S'` :$LOCALIP local redis become health." >> $LOGFILE
22 exit 0
23 else
24 echo "[ERROR]`date +'%Y-%m-%d:%H:%M:%S'` :$LOCALIP local redis is error." >> $LOGFILE
25 echo "[ERROR]`date +'%Y-%m-%d:%H:%M:%S'` :$LOCALIP shutdown local keepalived." >> $LOGFILE
26 /etc/init.d/keepalived stop
27 if [ "$?" != "0" ];then
28 echo "[ERROR]`date +'%Y-%m-%d:%H:%M:%S'` :$LOCALIP keepalived shutdown error." >> $LOGFILE
29 else
30 echo "[INFO]`date +'%Y-%m-%d:%H:%M:%S'` :$LOCALIP keepalived shutdown completed." >> $LOGFILE
31 fi
32 exit 1
33 fi
34fi
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vi /usr/local/keepalived/etc/keepalived/scripts/master.sh
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2KPATH=/usr/local/keepalived
3RPATH=/usr/local/redis
4REDISCLI=$RPATH/bin/redis-cli
5LOGFILE=$KPATH/logs/redis-state.log
6LOCALIP="192.168.1.218"
7REMOTEIP="192.168.1.219"
8PORT="6379"
9PID=$$
10
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12#当此服务器的keepalived恢复成master时，即虚拟IP切换到本机时，将本机的redis切换成role:master
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14echo "[WARM]-----------keepalived change to master,change local redis to master---------------" >> $LOGFILE
15echo "`date +'%Y-%m-%d:%H:%M:%S'`|$PID|state:[slave]" >> $LOGFILE
16#先切换成role:slave
17echo "`date +'%Y-%m-%d:%H:%M:%S'`|$PID|state:[slave] Run 'SLAVEOF $REMOTEIP $PORT'" >> $LOGFILE
18$REDISCLI SLAVEOF $REMOTEIP $PORT >> $LOGFILE 2>&1
19#同步数据
20echo "`date +'%Y-%m-%d:%H:%M:%S'`|$PID|state:[slave] wait 10 sec for data sync from old master" >> $LOGFILE
21sleep 10
22#等待10秒（此时间要根据实际业务需要进行调整），待数据同步完，再切换成role：master
23echo "`date +'%Y-%m-%d:%H:%M:%S'`|$PID|state:[slave] data rsync from old mater ok..." >> $LOGFILE
24echo "`date +'%Y-%m-%d:%H:%M:%S'`|$PID|state:[master] Run slaveof no one,close master/slave" >> $LOGFILE
25$REDISCLI SLAVEOF NO ONE >> $LOGFILE 2>&1
26echo "`date +'%Y-%m-%d:%H:%M:%S'`|$PID|state:[master] wait other slave connect...." >> $LOGFILE
27echo "-------------------------------------complete!------------------------------------------" >> $LOGFILE
28
#######################################################################
vi /usr/local/keepalived/etc/keepalived/scripts/backup.sh
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2KPATH=/usr/local/keepalived
3RPATH=/usr/local/redis
4REDISCLI=$RPATH/bin/redis-cli
5LOGFILE=$KPATH/logs/redis-state.log
6LOCALIP="192.168.1.218"
7REMOTEIP="192.168.1.219"
8PORT="6379"
9PID=$$
10
11
12#当此服务器的keepalived恢复成slave时，即虚拟IP切换到其他服务器时，将本机redis切换成role:slave
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14echo "[WARM]------------keepalived change to slave,change local redis to slave----------------" >> $LOGFILE
15echo "`date +'%Y-%m-%d:%H:%M:%S'`|$PID|state:[master]" >> $LOGFILE
16echo "`date +'%Y-%m-%d:%H:%M:%S'`|$PID|state:[master] Being slave state..." >> $LOGFILE 2>&1
17#切换时，等待10秒，让对方同步数据（此时间要根据实际业务需要进行调整）
18echo "`date +'%Y-%m-%d:%H:%M:%S'`|$PID|state:[master] wait 10 sec for data sync from old master" >> $LOGFILE
19sleep 10
20echo "`date +'%Y-%m-%d:%H:%M:%S'`|$PID|state:[master] data rsync from old mater ok..." >> $LOGFILE
21#等数据同步完，再切换成role：slave
22echo "`date +'%Y-%m-%d:%H:%M:%S'`|$PID|state:[slave] Run 'SLAVEOF $REMOTEIP $PORT'" >> $LOGFILE
23$REDISCLI SLAVEOF $REMOTEIP $PORT >> $LOGFILE 2>&1
24echo "`date +'%Y-%m-%d:%H:%M:%S'`|$PID|state:[slave] slave connect to $REMOTEIP $PORT ok..." >> $LOGFILE
25echo "-------------------------------------complete!------------------------------------------" >> $LOGFILE
26
#######################################################################
vi /usr/local/keepalived/etc/keepalived/scripts/stop.sh
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2KPATH=/usr/local/keepalived
3RPATH=/usr/local/redis
4REDISCLI=$RPATH/bin/redis-cli
5LOGFILE=$KPATH/logs/redis-state.log
6LOCALIP="192.168.1.218"
7REMOTEIP="192.168.1.219"
8PORT="6379"
9PID=$$
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12#当主服务器的keepalived停止时，将本机redis切换成role:slave
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14echo "[ERROR]-----------------keepalived stop,change local redis to slave---------------------" >> $LOGFILE
15echo "`date +'%Y-%m-%d:%H:%M:%S'`|$PID|state:[master]" >> $LOGFILE
16echo "`date +'%Y-%m-%d:%H:%M:%S'`|$PID|state:[master] Being slave state..." >> $LOGFILE 2>&1
17#切换时，等待10秒，让对方同步数据（此时间要根据实际业务需要进行调整）
18echo "`date +'%Y-%m-%d:%H:%M:%S'`|$PID|state:[master] wait 10 sec for data sync from old master" >> $LOGFILE
19sleep 10
20echo "`date +'%Y-%m-%d:%H:%M:%S'`|$PID|state:[master] data rsync from old mater ok..." >> $LOGFILE
21#等数据同步完，再切换成role：slave
22echo "`date +'%Y-%m-%d:%H:%M:%S'`|$PID|state:[slave] Run 'SLAVEOF $REMOTEIP $PORT'" >> $LOGFILE
23$REDISCLI SLAVEOF $REMOTEIP $PORT >> $LOGFILE 2>&1
24echo "`date +'%Y-%m-%d:%H:%M:%S'`|$PID|state:[slave] slave connect to $REMOTEIP $PORT ok..." >> $LOGFILE
25echo "-------------------------------------complete!------------------------------------------" >> $LOGFILE
26
#######################################################################
vi /usr/local/keepalived/etc/keepalived/scripts/fault.sh
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2KPATH=/usr/local/keepalived
3RPATH=/usr/local/redis
4REDISCLI=$RPATH/bin/redis-cli
5LOGFILE=$KPATH/logs/redis-state.log
6LOCALIP="192.168.1.218"
7REMOTEIP="192.168.1.219"
8PORT="6379"
9PID=$$
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12#当此服务器的keepalived出错时，将本机redis切换成role:slave
13echo "[ERROR]---------------keepalived is fault,change local redis to slave-------------------" >> $LOGFILE
14echo "`date +'%Y-%m-%d:%H:%M:%S'`|$PID|state:[master]" >>$LOGFILE
15echo "`date +'%Y-%m-%d:%H:%M:%S'`|$PID|state:[master] Being slave state..." >> $LOGFILE 2>&1
16#切换时，等待10秒，让对方同步数据（此时间要根据实际业务需要进行调整）
17echo "`date +'%Y-%m-%d:%H:%M:%S'`|$PID|state:[master] wait 10 sec for data sync from old master" >> $LOGFILE
18sleep 10
19echo "`date +'%Y-%m-%d:%H:%M:%S'`|$PID|state:[master] data rsync from old mater ok..." >> $LOGFILE
20#等数据同步完，再切换成role：slave
21echo "`date +'%Y-%m-%d:%H:%M:%S'`|$PID|state:[slave] Run 'SLAVEOF $REMOTEIP $PORT'" >> $LOGFILE
22$REDISCLI SLAVEOF $REMOTEIP $PORT >> $LOGFILE 2>&1
23echo "`date +'%Y-%m-%d:%H:%M:%S'`|$PID|state:[slave] slave connect to $REMOTEIP $PORT ok..." >> $LOGFILE
24echo "-------------------------------------complete!------------------------------------------" >> $LOGFILE
25
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系统测试
注意：
(1).在keepalived.conf配置文件中，将keepalived双机 都设置成BACKUP.同时在218上设置了nopreempt，即恢复时不抢占。而规划中是将218作为master。所以在启动过程中要遵循以下顺序：先启动218上的keepalived，等待数据同步完成后，再启动219上的keepalived.
(2).在keepalived的巡检脚本redis_check.sh中加入了状态切换的监控脚本。在master.sh中设置了当keepalived切换成master，会先将redis切换成slave进行同步数据，再切换回master。所以在启动keepalived之前，要保证Master和Slave上redis的数据是一致的，这样先启动redis的master那台的keepalived，虽然redis master会连接到redis slave同步数据，但是两边数据在刚开始的时候是一致的，并不会产生什么问题。
(3).在实际生产环境中需要修改防火墙策略，开放相应的端口。在此直接先将防火墙关闭:service iptables stop。
以下为各种测试场景和输出结果：
—————————————–初始环境————————————————–
设定一下初始环境：
—-启动218和219的redis: /usr/local/redis/redis-start.sh
—-启动218的keepalived: service keepalived start;先不启动219的keepalived.
在218上执行tail �f /usr/local/keepalived/logs/keepalived.log，可看到keepavlived切换成master state(配置文件中是设置state:backup),且绑定了VIP。
查看218Master:redis的日志，可以看到redis切换的过程如下：
—-启动219Slave的keepalived，并查看redis的日志，可以看到redis的状态变成了slave：
—————————————–初始环境————————————————–
—————————————–设计思路3————————————————-
—-模拟设计思路3，将218Master的redis进程kill掉:
此时218的keepalived会被停止，如下图：
219的keepalived会正确切换成State:Master,VIP完成漂移，如下图：
218的redis监控日志如下，
219的redis监控日志如下，显示了219已切换成master，保证了业务（当然此处218在内存中未写入文件的数据会丢失）：
—-模拟218从故障中恢复：
因为在发现故障时，会将218上的keepalived关闭，因此恢复时，需要先启动218的redis，然后再启动218的keepalived：
查看218的keepalived日志，218的keepalived直接进入state:backup,不会造成业务的来回切换：
查看218的redis日志，218的redis启动后，会切换成已存在redis服务器的备机。
综上所示，设计思路3测试成功。
—————————————–设计思路3————————————————-
—————————————–设计思路2————————————————-
—-先设置成初始环境，再模拟设计思路2，将218的keepalived进程kill掉（service keepalived stop）:
查看218的redis监控日志：
查看219的keepalivd日志，说明keepalived正常切换了：
查看219的redis监控日志，可以看到redis完成了主从切换：
—-模拟218从keepalived故障中恢复（只需要先kill所有keepalived进程后正常启动），执行service keepalived start:
查看219的keepalived的日志，可以看到keepalived的state为backup，不会造成VIP的漂移：
查看218的redis监控日志，可
查看218的redis运行日志，可以看到redis恢复为slave身份，不会造成业务切换：
综上所示，设计思路2测试成功。
—————————————–设计思路2————————————————-
设计思路4即为初始环境，设计思路1的情况为设计思路2和3的综合情况，无需测试了。
以上即为Redis双机热备方案。
