CentOS7 安装keepalived 实现 nginx 主备高可用

0x00 实验环境

本次实验所用环境如下：

虚拟机：VirtualBox 6.1 创建的两台CentOS7虚拟机

OS：CentOS Linux release 7.7.1908 (Core)

Nginx ：nginx version: nginx/1.20.1
Keepalived：Keepalived v1.3.5 (03/19,2017), git commit v1.3.5-6-g6fa32f2

限制：此方法要求服务器的hostname必须不能包含“nginx”字符串，否则可能会影响到监控脚本的执行（未验证）。



0x01 禁用SELinux：

sed -i 's/SELINUX=enforcing/SELINUX=disabled/'  /etc/selinux/config
setenforce 0

0x02 安装epel：

rpm --import https://www.elrepo.org/RPM-GPG-KEY-elrepo.org
yum install https://www.elrepo.org/elrepo-release-7.el7.elrepo.noarch.rpm

0x03 安装keepalived：

yum install keepalived -y

运行日志位置：
/var/log/messages

0x04 修改配置文件：
master节点配置文件内容（vim /etc/keepalived/keepalived.conf）：

! Configuration File for keepalived

global_defs {
   router_id LVS_nginx1
}

vrrp_script trackngx {
    script "/root/chk_nginx_pid.sh"
    interval 5
}

vrrp_instance VI_1 {
    state MASTER
    interface enp0s3
    virtual_router_id 51
    priority 150
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 51yunjiance.com
    }
    virtual_ipaddress {
        172.171.19.238
    }
    track_script  {
        trackngx
    }
}

backup节点配置文件内容（vim /etc/keepalived/keepalived.conf）：

! Configuration File for keepalived


global_defs {
   router_id LVS_nginx2
}

vrrp_script trackngx {
    script "/root/chk_nginx_pid.sh"
    interval 5
}

vrrp_instance VI_1 {
    state BACKUP
    interface enp0s3
    virtual_router_id 51
    priority 100
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 51yunjiance.com
    }
    virtual_ipaddress {
        172.171.19.238
    }
    track_script  {
        trackngx
    }
}

0x05 添加监控nginx进程脚本（两台机器都要添加）：

该脚本会尝试先启动nginx，如果启动失败，则停止keepalived服务，保证节点顺利下线。

注意，此脚本会自动启动nginx，可能对运维时产生一定的影响。
vim /root/chk_nginx_pid.sh

#!/bin/sh

nginxpid=$(ps -C nginx --no-header | wc -l)
if [ $nginxpid -eq 0 ]
then
    systemctl start nginx
    sleep 3
    nginxpid=$(ps -C nginx --no-header | wc -l)
    if [ $nginxpid -eq 0 ];then
            systemctl stop keepalived
    fi
fi

修改为可执行文件：

chmod +x chk_nginx_pid.sh

0x06 设置自启动并启动keepalived
keepalived随系统自启动：
systemctl enable keepalived
启动keepalived：
systemctl start keepalived

0x07 验证

手动停止nginx后会自动拉起nginx，关闭其中一台主机后，另外一台主机稍后会自动接管虚拟IP。