原理：

Memcached主主复制是指在任意一台Memcached服务器修改数据都会被同步到另外一台，但是Memcached API客户端是无法判断连接到哪一台Memcached服务器的，所以需要设置VIP地址，提供给Memcached API客户端进行连接。可以使用Keepalived产生的VIP地址连接主Memcached服务器，并且提供高可用架构。

使用两台Memcached服务器，一台客户机来完成，实验环境表如下：

1.配置memcached主缓存节点和从缓存节点-----两台配置相同

[root@localhost ~]# tar zxvf libevent-2.1.8-stable.tar.gz -C /opt/   //解包// [root@localhost ~]# tar zxvf memcached-1.5.6.tar.gz -C /opt/ [root@localhost ~]# mkdir /opt/magent [root@localhost ~]# tar zxvf magent-0.5.tar.gz -C /opt/magent/  [root@localhost opt]#cd libevent-2.1.8-stable/ [root@localhost libevent-2.1.8-stable]# yum install gcc gcc-c++ make -y [root@localhost libevent-2.1.8-stable]# ./configure --prefix=/usr [root@localhost libevent-2.1.8-stable]# make && make install [root@localhost libevent-2.1.8-stable]# cd ../memcached-1.5.6/ [root@localhost memcached-1.5.6]# ./configure --with-libevent=/usr [root@localhost memcached-1.5.6]# ln -s /usr/lib/libevent-2.1.so.6 /usr/lib64/libevent-2.1.so.6    //软链接//

2.关闭防火墙并开启memcached服务

[root@localhost memcached-1.5.6]# systemctl stop firewalld.service [root@localhost memcached-1.5.6]# setenforce 0[root@localhost memcached-1.5.6]# memcached -d -m 32m -p 11211 -u root[root@localhost memcached-1.5.6]# netstat -ntap | grep 11211tcp        0      0 0.0.0.0:11211           0.0.0.0:*               LISTEN      11224/memcached     tcp6       0      0 :::11211                :::*                    LISTEN      11224/memcached

3.在主服务器上安装magent

[root@localhost memcached-1.5.6]# cd /opt/magent/[root@localhost magent]# lsketama.c  ketama.h  magent.c  Makefile[root@localhost magent]# vim ketama.h#ifndef SSIZE_MAX#define SSIZE_MAX 32767#endif[root@localhost magent]# vim Makefile LIBS = -levent -lm //第一行末尾加-lm （不是数字1LIBS = -levent -lmCFLAGS = -Wall -O2 -g[root@localhost magent]# makegcc -Wall -O2 -g  -c -o magent.o magent.cgcc -Wall -O2 -g  -c -o ketama.o ketama.cgcc -Wall -O2 -g -o magent magent.o ketama.o -levent -lm

4.把生成的mgent程序让系统识别

ls一下可看到magent可执行程序[root@localhost magent]# lsketama.c  ketama.h  ketama.o  magent  magent.c  magent.o  Makefile[root@localhost magent]# cp magent /usr/bin/

5.把产生的magent文件直接复制到从服务器。

[root@localhost bin]# yum install openssh-clients -y[root@localhost bin]# scp magent root@192.168.126.166:/usr/bin/

6.安装keepalived，修改默认配置文件。

[root@localhost bin]# yum install keepalived -y[root@localhost bin]# vim /etc/keepalived/keepalived.conf ! Configuration File for keepalivedvrrp_script magent {        script "/opt/shell/magent.sh"        interval 2}global_defs {   notification_email {     acassen@firewall.loc     failover@firewall.loc     sysadmin@firewall.loc   }   notification_email_from Alexandre.Cassen@firewall.loc   smtp_server 192.168.200.1   smtp_connect_timeout 30   router_id MAGENT_HA    //主服务器名称//}vrrp_instance VI_1 {    state MASTER    interface ens33     //网卡名称//    virtual_router_id 51    priority 100    //优先级//    advert_int 1    authentication {        auth_type PASS        auth_pass 1111       }    virtual_ipaddress {        192.168.126.188     //虚拟IP//    }track_script {        magent     //函数//}}

7.从服务器上安装keepalived，配置文件进行修改。

[root@localhost bin]# vim /etc/keepalived/keepalived.conf ! Configuration File for keepalivedvi keepalived.confvrrp_script magent {        script "/opt/shell/magent.sh"        interval 2}global_defs {   notification_email {     acassen@firewall.loc     failover@firewall.loc     sysadmin@firewall.loc   }   notification_email_from Alexandre.Cassen@firewall.loc   smtp_server 192.168.200.1   smtp_connect_timeout 30   router_id MAGENT_HB      //从服务器的名称//}vrrp_instance VI_1 {    state BACKUP            //从服务器的热备状态要修改成BACKUP//    interface ens33  //网卡名称//    virtual_router_id 52    //不能与主服务器相同//    priority 90       //从调度器的优先级要小于主的//    advert_int 1    authentication {        auth_type PASS        auth_pass 1111    }    virtual_ipaddress {        192.168.126.188     //虚拟IP//    }track_script {        //函数//        magent  }}

8.在主服务器上设置magent管理脚本

[root@localhost bin]# mkdir /opt/shell[root@localhost bin]# vim /opt/shell/magent.sh#!/bin/bashK=`ps -ef | grep keepalived | grep -v grep | wc -l`if [ $K -gt 0 ]; then        magent -u root -n 51200 -l 192.168.126.188 -p 12000 -s 192.168.126.138:11211 -b 192.168.126.166:11211elsepkill -9 magentfi参数注解：-n 51200 //定义用户最大连接数-l 192.168.126.188 //指定虚拟IP-p 12000  //指定端口号-s //指定主缓存服务器-b //指定从缓存服务器[root@localhost shell]# chmod +x magent.sh   // 增加执行权限//

9.在从服务器上操作

[root@localhost bin]# mkdir /opt/shell[root@localhost bin]# cd /opt/shell/[root@localhost shell]# vim magent.sh[root@localhost shell]# vim magent.sh脚本内容如下，与主服务器脚本有区别！#!/bin/bashK=`ip addr | grep 192.168.126.188 | grep -v grep | wc -l`if [ $K -gt 0 ]; then        magent -u root -n 51200 -l 192.168.126.188 -p 12000 -s 192.168.126.138:11211 -b 192.168.126.166:11211elsepkill -9 magentfi  [root@localhost shell]# chmod +x magent.sh

10.开始验证

1）启动主服务器

[root@localhost shell]# systemctl start keepalived.service [root@localhost shell]# netstat -ntap | grep 12000  //确认magent运行//tcp        0      0 192.168.126.188:12000   0.0.0.0:*               LISTEN      12422/magent

2）启动从服务器

[root@localhost shell]# systemctl start keepalived.service [root@localhost shell]# netstat -ntap | grep 12000tcp        0      0 192.168.126.188:12000   0.0.0.0:*               LISTEN      11716/magent

3）在主服务器上使用telnet进行简单验证复制功能

[root@localhost shell]# telnet 192.168.126.188 12000  //用漂移地址登陆服务//Trying 192.168.126.188...Connected to 192.168.126.188.Escape character is '^]'.add username 0 0 7      //添加一条键值数据//1234567STORED在从服务器上查看[root@localhost shell]# telnet 192.168.126.188 12000 Trying 192.168.126.188...Connected to 192.168.126.188.Escape character is '^]'.get username    //查看键值数据VALUE username 0 71234567         //内容存在，写入成功//END

11.在客户端用漂移地址登陆服务

[root@localhost ~]# yum install telnet -y[root@localhost ~]# telnet 192.168.126.188 12000 Trying 192.168.126.188...Connected to 192.168.126.188.Escape character is '^]'.add username 0 0 8    //添加一条键值数据//12345678STORED

1）在主服务器和从服务器上查看是否写入成功。

主服务器get usernameVALUE username 0 812345678END从服务器get usernameVALUE username 0 812345678END

2）把主服务器停了业务不影响

[root@localhost shell]# systemctl stop keepalived.service[root@localhost shell]# ip addrinet 192.168.126.138/24 brd 192.168.126.255 scope global dynamic ens33

3）在从服务器上查看

[root@localhost shell]# ip addrinet 192.168.126.166/24 brd 192.168.126.255 scope global dynamic ens33       valid_lft 1146sec preferred_lft 1146sec    inet 192.168.126.188/32 scope global ens33可以看到漂移地址已经转移到从服务器上了，说明从已接受工作。

3）再把主服务器开启

[root@localhost shell]# systemctl start keepalived.service [root@localhost shell]# ip addrinet 192.168.126.138/24 brd 192.168.126.255 scope global dynamic ens33       valid_lft 1145sec preferred_lft 1145sec    inet 192.168.126.188/32 scope global ens33       valid_lft forever preferred_lft forever漂移地址再次转移到主服务器上，接手地址，服务依然不受影响。

实验成功