前面的lvs虽然已经配置成功也实现了负载均衡，但是我们测试的时候发现，当某台real server把nginx进程停掉，那么director照样会把请求转发过去，这样就造成了某些请求不正常。所以需要有一种机制用来检测real server的状态，这就是keepalived。它的作用除了可以检测rs状态外，还可以检测备用director的状态，也就是说keepalived可以实现ha集群的功能，当然了也需要一台备用director。
备用director也需要安装一下keepalived软件、ipvsadm；
keepalived调用lvs来实现自己的规则；
yum install -y keepalived ipvsadm
环境搭建工作：
主director 192.168.11.30 eth1网卡
从director 192.168.11.40 eth1网卡
real server1: 192.168.11.100 eth0网卡
real server2: 192.168.11.101 eth0网卡
用来curl测试的linux主机 192.168.11.0 网段即可；
主dr和备用dr都需要安装keepalived，ipvsadm；
两台rs安装nginx；
安装好后，主director的配置文件
vim /etc/keepalived/keepalived.conf //加入如下：
vrrp_instance VI_1 {
state MASTER #备用服务器上为 BACKUP
interface eth1
virtual_router_id 51
priority 100 #优先级，数值越大优先级越高；备用服务器上为90
advert_int 1
authentication {
auth_type PASS
auth_pass 1111
}
virtual_ipaddress {
192.168.11.110
}
}
virtual_server 192.168.11.110 80 {
delay_loop 6 #(每隔6秒查询realserver状态，是否存活)
lb_algo wlc #(轮询算法)
lb_kind DR #(Direct Route)
persistence_timeout 0 #(同一IP的连接多少秒内被分配到同一台realserver，0表示不连接)
protocol TCP #(用TCP协议检查realserver状态)
real_server 192.168.11.100 80 {
weight 100 #(权重)
TCP_CHECK {
connect_timeout 10 #(10秒无响应超时)
nb_get_retry 3
delay_before_retry 3
connect_port 80
}
}
real_server 192.168.11.101 80 {
weight 100
TCP_CHECK {
connect_timeout 10
nb_get_retry 3
delay_before_retry 3
connect_port 80
}
}
}
从director的配置文件只需要修改下面两项：
state MASTER -> state BACKUP
priority 100 -> priority 90
配置完keepalived后，需要开启端口转发（主从dr都要做）：
echo 1 > /proc/sys/net/ipv4/ip_forward
然后，两个rs上执行 /usr/local/sbin/lvs_dr_rs.sh 脚本，启动nginx服务
# /etc/init.d/nginx start
最后，两个director上启动keepalived服务（先主后从）：
# /etc/init.d/keepalived start
另外，需要注意的是，启动keepalived服务会自动生成vip和ipvsadm规则.
使用命令#ip addr 查看dr的虚拟ip地址；直接使用ifconfig不显示虚拟ip；
[[email protected] keepalived]# ip addr eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UNKNOWN qlen 1000 link/ether 00:0c:29:97:c3:f6 brd ff:ff:ff:ff:ff:ff inet 192.168.11.30/24 brd 192.168.11.255 scope global eth1 inet 192.168.11.110/32 scope global eth1 inet6 fe80::20c:29ff:fe97:c3f6/64 scope link valid_lft forever preferred_lft forever
在其他机器curl测试，请求rs1和rs2次数相当；
[[email protected] ~]# curl 192.168.11.110 rs1rs1 [[email protected] ~]# curl 192.168.11.110 rs2rs2 [[email protected] ~]# curl 192.168.11.110 rs1rs1 [[email protected] ~]# curl 192.168.11.110 rs2rs2
rs2上面stop nginx，然后curl测试，发现所有的请求都到rs1上面了；
日志里面也会记录remove rs2；日志文件：/var/log/messages
[[email protected] ~]# /etc/init.d/nginx stop
[[email protected] ~]# curl 192.168.11.110 rs1rs1 [[email protected] ~]# curl 192.168.11.110 rs1rs1 [[email protected] ~]# curl 192.168.11.110 rs1rs1 [[email protected] ~]# curl 192.168.11.110 rs1rs1
[[email protected] ~]# tail -2 /var/log/messages Jun 9 23:27:19 localhost Keepalived_healthcheckers[1572]: TCP connection to [192.168.11.101]:80 failed !!! Jun 9 23:27:19 localhost Keepalived_healthcheckers[1572]: Removing service [192.168.11.101]:80 from VS [192.168.11.110]:80
rs2启动nginx，日志文件记录adding rs2；curl测试，发现请求平均分配到rs1和rs2上面了；
[[email protected] ~]# /etc/init.d/nginx start
[[email protected] ~]# tail -2 /var/log/messages Jun 9 23:31:38 localhost Keepalived_healthcheckers[1572]: TCP connection to [192.168.11.101]:80 success. Jun 9 23:31:38 localhost Keepalived_healthcheckers[1572]: Adding service [192.168.11.101]:80 to VS [192.168.11.110]:80
[[email protected] ~]# curl 192.168.11.110 rs1rs1 [[email protected] ~]# curl 192.168.11.110 rs2rs2 [[email protected] ~]# curl 192.168.11.110 rs1rs1 [[email protected]alhost ~]# curl 192.168.11.110 rs2rs2
加入dr2 备用dircetor机器；
主上停止keepalive服务；stop之后，在从上ip addr查看绑定虚拟ip，说明从接管了服务；切换速度很快；
主上启动keepalived服务后，主绑定虚拟ip，接管服务；
[[email protected] keepalived]# ip addr eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UNKNOWN qlen 1000 link/ether 00:0c:29:af:73:3f brd ff:ff:ff:ff:ff:ff inet 192.168.11.40/24 brd 192.168.11.255 scope global eth1 inet 192.168.11.110/32 scope global eth1
nc命令可以扫描端口是否打开：
在其他机器上扫描，11.100 和11.101，11.110的80端口是否打开；
#nc -z -w2 192.168.11.110 80
[[email protected] ~]# nc -z -w2 192.168.11.100 80 Connection to 192.168.11.100 80 port [tcp/http] succeeded! [[email protected] ~]# nc -z -w2 192.168.11.101 80 Connection to 192.168.11.101 80 port [tcp/http] succeeded! [[email protected] ~]# nc -z -w2 192.168.11.110 80 Connection to 192.168.11.110 80 port [tcp/http] succeeded!