Implementing High Availability for Nginx with Keepalived: A Step‑by‑Step Guide

High Availability (HA) refers to designing distributed systems to minimize downtime, ensuring services remain accessible as much as possible.

The article addresses the problem of Nginx failure in production, where a single point of failure can render all external interfaces inaccessible, and proposes using Keepalived to achieve HA.

It explains the double‑machine hot‑standby model, where one server actively provides the service while a second server stands by to take over automatically upon failure.

Keepalived, originally built for LVS, provides VRRP‑based failover and can manage services such as Nginx, HAProxy, MySQL, etc.

The implementation steps include preparing two virtual machines (192.168.16.128 and 192.168.16.129) with Nginx installed, installing Keepalived via yum, and configuring the keepalived.conf files on both master and backup nodes.

rpm -ivh http://nginx.org/packages/centos/7/noarch/RPMS/nginx-release-centos-7-0.el7.ngx.noarch.rpm
wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/CentOS-7.repo

yum -y install nginx

systemctl start nginx; #启动Nginx
systemctl stop nginx; #停止Nginx

yum -y install keepalived

# keepalived.conf (master)
vrrp_script chk_http_port {
    script "/usr/local/src/check_nginx_pid.sh"
    interval 2
    weight 2
}
vrrp_instance VI_1 {
    state MASTER
    interface ens33
    virtual_router_id 66
    priority 100
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 1111
    }
    track_script {
        chk_http_port
    }
    virtual_ipaddress {
        192.168.16.130
    }
}

# keepalived.conf (backup)
vrrp_script chk_http_port {
    script "/usr/local/src/check_nginx_pid.sh"
    interval 2
    weight 2
}
vrrp_instance VI_1 {
    state BACKUP
    interface ens33
    virtual_router_id 66
    priority 99
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 1111
    }
    track_script {
        chk_http_port
    }
    virtual_ipaddress {
        192.168.16.130
    }
}

#!/bin/bash
#检测nginx是否启动了
A=`ps -C nginx --no-header |wc -l`
if [ $A -eq 0 ]; then
    systemctl start nginx
    if [ `ps -C nginx --no-header |wc -l` -eq 0 ]; then
        killall keepalived
    fi
fi

chmod 775 check_nginx_pid.sh

After configuring the virtual IP (VIP) 192.168.16.130, accessing the VIP initially serves the master node; stopping Nginx on the master triggers the script to restart it, and if the master goes down, the backup node automatically takes over the VIP, demonstrating a complete enterprise‑grade HA solution.

The article notes that Keepalived also supports additional features such as email alerts, which can be explored in its official documentation.