Memcached主主复制+Keepalived高可用：
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。
Memcached的复制功能支持多个Memcached之间进行互相复制(双向复制，主备都是可读可写的)，可以解决Memcached的容灾问题
因为Memcached主主复制这种架构，在程序连接时不知道应该连接到哪个服务器，所以需要在前端家VIP地址，实现高可用架构。这里用Keepalived实现，因而Keepalived的作用是用来检测Memcached服务器状态是否正常
Keepalived不断检测Memcached主服务器的11211端口，如果检测到Memcached服务发生宕机或死机等情况，就会将VIP从主服务器移至从服务器，从而实现Memcached的高可用性
要使用Memcached复制架构，需要下载支持复制功能的Memcached安装包：
路径：
https://sourceforge.net/repcached/memcached-1.2.8-repcached-2.2.tar.gz
实验环境：
192.168.1.101 master libevent-1.4.14b-stable.tar.gz memcached-1.2.8-repcached-2.2.tar.gz
192.168.1.102 backup libevent-1.4.14b-stable.tar.gz memcached-1.2.8-repcached-2.2.tar.gz
先决条件：
1.关闭防火墙和SELINUX
2.配置本地yum源
1.安装libevent-1.4.14b-stable.tar.gz
[root@master opt]# tar xf libevent-1.4.14b-stable.tar.gz
[root@master opt]# cd libevent-1.4.14b-stable
[root@master libevent-1.4.14b-stable]# ./configure --prefix=/usr/local/libevent && make && make install
2.安装带有复制功能的Memcached
[root@master opt]# tar xf memcached-1.2.8-repcached-2.2.tar.gz
[root@master opt]# ls
libevent-1.4.14b-stable memcached-1.2.8-repcached-2.2
libevent-1.4.14b-stable.tar.gz memcached-1.2.8-repcached-2.2.tar.gz
[root@master opt]# cd memcached-1.2.8-repcached-2.2
[root@master memcached-1.2.8-repcached-2.2]# ./configure --prefix=/usr/local/memcached_replication --enable-replication --with-libevent=/usr/local/libevent && make && make install
3.启动Memcached服务
支持复制功能的Memcached安装完成之后，需要将编译安装的libevent-1.4.so.2模块复制到/usr/lib64目录下，否则在启动带有复制功能的Memcached服务时会报错
[root@backup memcached-1.2.8-repcached-2.2]# ln -s /usr/local/libevent/lib/libevent-1.4.so.2 /usr/lib64/
启动服务时，使用-x指定对端
[root@backup memcached-1.2.8-repcached-2.2]# /usr/local/memcached_replication/bin/memcached -d -u root -m 128 -x 192.168.1.101
[root@backup memcached-1.2.8-repcached-2.2]# netstat -anpt | grep memcached
tcp 0 0 0.0.0.0:11211 0.0.0.0:* LISTEN 7520/memcached
tcp 0 0 0.0.0.0:11212 0.0.0.0:* LISTEN 7520/memcached
tcp6 0 0 :::11211 :::* LISTEN 7520/memcached
4.使用telnet进行简单的验证复制功能
(1.)在master上插入一条具有特点的键值
[root@master opt]# telnet 192.168.1.101 11211
Trying 192.168.1.101...
Connected to 192.168.1.101.
Escape character is '^]'.
set username 0 0 8
20170226
STORED
get username
VALUE username 0 8
20170226
END
quit
Connection closed by foreign host.
(2.)在backup上面查看刚才插入的数据
[root@backup ~]# telnet 192.168.1.102 11211
Trying 192.168.1.102...
Connected to 192.168.1.102.
Escape character is '^]'.
get username
VALUE username 0 8
20170226
END
get username2
END
quit
Connection closed by foreign host
同理，在backup上插入的数据，在master上也可以查看到，这就是Memcached的主主复制
5.安装配置Keepalived
[root@master opt]# yum install keepalived -y
6.配置主Keepalived
! Configuration File for keepalived
global_defs {
router_id LVS_DEVEL
}
vrrp_sync_group cluster {
group {
mem_ba
}
}
vrrp_instance VI_1 {
state MASTER
interface ens33
virtual_router_id 51
priority 100
advert_int 1
authentication {
auth_type PASS
auth_pass 1111
}
virtual_ipaddress {
192.168.1.250
}
}
virtual_server 192.168.1.250 11211 {
delay_loop 6
persistence_timeout 20
protocol TCP
sorry_server 192.168.1.102 11211 # 对端
real_server 192.168.1.101 11211 { # 本机
weight 3
notify_down /root/memcached.sh
TCP_CHECK {
connect_timeout 3
nb_get_retry 3
delay_before_retry 3
connect_port 11211
}
}
}
设置执行脚本如下：
[root@master keepalived]# echo "/usr/bin/systemctl stop keepalived" > memcached.sh
[root@master keepalived]# chmod +x memcached.sh
7.配置备Keepalived
! Configuration File for keepalived
global_defs {
router_id LVS_DEVEL
}
vrrp_sync_group cluster {
group {
mem_ba
}
}
vrrp_instance VI_1 {
state MASTER
interface ens33
virtual_router_id 51
priority 90
advert_int 1
authentication {
auth_type PASS
auth_pass 1111
}
virtual_ipaddress {
192.168.1.250
}
}
virtual_server 192.168.1.250 11211 {
delay_loop 6
persistence_timeout 20
protocol TCP
sorry_server 192.168.1.101 11211
real_server 192.168.1.102 11211 {
weight 3
notify_down /root/memcached.sh
TCP_CHECK {
connect_timeout 3
nb_get_retry 3
delay_before_retry 3
connect_port 11211
}
}
}
同样设置脚本如下：
[root@backup ~]# echo "/usr/bin/systemctl stop keepalived" > memcached.sh
[root@backup ~]# chmod +x memcached.sh
8.测试验证
分别启动主从的keepalived服务
[root@master ~]# systemctl start keepalived
[root@backup ~]# systemctl start keepalived
(1.)验证主keepalived获取VIP
使用ip address show命令查看VIP地址：
[root@master ~]# ip a
2: ens33: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
link/ether 00:0c:29:5c:93:64 brd ff:ff:ff:ff:ff:ff
inet 192.168.1.101/24 brd 192.168.1.255 scope global ens33
valid_lft forever preferred_lft forever
inet 192.168.1.250/32 scope global ens33
valid_lft forever preferred_lft forever
inet6 fe80::f32f:df18:99a7:1152/64 scope link
valid_lft forever preferred_lft forever
(2.)验证高可用性
关闭master服务器的Memcached服务，在backup服务器上查看地址信息
[root@master ~]# killall memcached
[root@backup ~]# ip a
2: ens33: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
link/ether 00:0c:29:13:d9:b8 brd ff:ff:ff:ff:ff:ff
inet 192.168.1.102/24 brd 192.168.1.255 scope global noprefixroute ens33
valid_lft forever preferred_lft forever
inet 192.168.1.250/32 scope global ens33
valid_lft forever preferred_lft forever
inet6 fe80::832b:b762:6f75:d47b/64 scope link noprefixroute
valid_lft forever preferred_lft forever