详解Keepalived+Nginx实现高可用（HA）

shell> vi /etc/sysconfig/iptables 
-A INPUT -p vrrp -d 224.0.0.18/32 -j ACCEPT

firewall-cmd --direct --permanent --add-rule ipv4 filter INPUT 0 --in-interface enp4s0 --destination 224.0.0.18 --protocol vrrp -j ACCEPT
firewall-cmd --reload

shell> vi /etc/sysconfig/selinux
#修改:
SELINUX=disabled
#setenforce 0

global_defs {
 router_id nginx_01 #标识本节点的名称，通常为hostname
}

## keepalived会定时执行脚本并对脚本执行的结果进行分析,动态调整vrrp_instance的优先级。
##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。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。其他情况,维持原本配置的优先级,即配置文件中priority对应的值。
vrrp_script chk_nginx {
  script "/etc/keepalived/nginx_check.sh"
  interval 2 #每2秒检测一次nginx的运行状态
  weight -20 #失败一次，将自己的优先级-20
}

vrrp_instance VI_1 {
 state MASTER     # 状态，主节点为MASTER，备份节点为BACKUP
 interface enp0s3    # 绑定VIP的网络接口，通过ifconfig查看自己的网络接口
 virtual_router_id 51   # 虚拟路由的ID号,两个节点设置必须一样,可选IP最后一段使用,相同的VRID为一个组,他将决定多播的MAC地址
 mcast_src_ip 192.168.1.201 # 本机IP地址
 priority 100     # 节点优先级，值范围0～254，MASTER要比BACKUP高
 advert_int 1     # 组播信息发送时间间隔，两个节点必须设置一样，默认为1秒
 # 设置验证信息，两个节点必须一致
 authentication {
  auth_type PASS
  auth_pass 1111
 }
 # 虚拟IP，两个节点设置必须一样。可以设置多个，一行写一个
 virtual_ipaddress {
  192.168.1.210
 }

 track_script {
  chk_nginx # nginx存活状态检测脚本
 }
}

global_defs {
 router_id nginx_02
}

vrrp_script chk_nginx {
 script "/etc/keepalived/nginx_check.sh"
 interval 2
 weight -20
}

vrrp_instance VI_1 {
 state BACKUP
 interface enp0s3
 virtual_router_id 51
 mcast_src_ip 192.168.1.202
 priority 90
 advert_int 1
 authentication {
  auth_type PASS
  auth_pass 1111
 }
 virtual_ipaddress {
  192.168.1.210
 }

 track_script {
  chk_nginx
 }
}

#!/bin/bash
A=`ps -C nginx --no-header | wc -l`
if [ $A -eq 0 ];then
 /opt/nginx/sbin/nginx #尝试重新启动nginx
 sleep 2 #睡眠2秒
 if [ `ps -C nginx --no-header | wc -l` -eq 0 ];then
  killall keepalived #启动失败，将keepalived服务杀死。将vip漂移到其它备份节点
 fi
fi

shell> service keepalived start
shell> ps -ef | grep keepalived
[root@localhost ~]# ps -ef | grep keepalived
root  865  1 0 23:36 ?  00:00:00 keepalived -D
root  869 865 0 23:36 ?  00:00:00 keepalived -D
root  870 865 0 23:36 ?  00:00:00 keepalived -D

shell> service keepalived stop
shell> ip addr

shell> service keepalived start

global_defs {
 router_id nginx_01 #标识本节点的名称，通常为hostname
}

vrrp_script chk_nginx {
  script "/etc/keepalived/nginx_check.sh"
  interval 2 
  weight -20
}

vrrp_instance VI_1 {
 state BACKUP     
 interface enp0s3    
 virtual_router_id 51   
 mcast_src_ip 192.168.1.201 
 priority 100     
 advert_int 1     
 nopreempt
 authentication {
  auth_type PASS
  auth_pass 1111
 }
 virtual_ipaddress {
  192.168.1.210
 }

 track_script {
  chk_nginx # nginx存活状态检测脚本
 }
}

global_defs {
 router_id nginx_02
}

vrrp_script chk_nginx {
 script "/etc/keepalived/nginx_check.sh"
 interval 2
 weight -20
}

vrrp_instance VI_1 {
 state BACKUP
 interface enp0s3
 virtual_router_id 51
 mcast_src_ip 192.168.1.202
 priority 90
 advert_int 1
 nopreempt
 authentication {
  auth_type PASS
  auth_pass 1111
 }
 virtual_ipaddress {
  192.168.1.210
 }
 track_script {
  chk_nginx
 }
}