KeepAlived + HAProxy: توازن بار با دسترس‌پذیری بالا

کلاینت‌ها → [IP مجازی: 10.0.0.100]
                  |
    [HAProxy-1 (Master)]  [HAProxy-2 (Backup)]
         |                      |
    [Web-1:80]  [Web-2:80]  [Web-3:80]

frontend web-frontend
    bind *:80
    bind *:443 ssl crt /etc/haproxy/certs/combined.pem
    redirect scheme https if !{ ssl_fc }
    default_backend web-servers

backend web-servers
    balance roundrobin
    option httpchk GET /health HTTP/1.1
Host: localhost
    server web-1 10.0.1.10:80 check inter 2s rise 2 fall 3
    server web-2 10.0.1.11:80 check inter 2s rise 2 fall 3

vrrp_instance VI_1 {
    state MASTER
    interface eth0
    virtual_router_id 51
    priority 100
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass YourSecretPass123
    }
    virtual_ipaddress {
        10.0.0.100/24 dev eth0
    }
}

while true; do curl -s http://10.0.0.100/ | grep "server"; sleep 1; done
systemctl stop haproxy  # روی master
# IP مجازی باید ظرف ۲-۴ ثانیه به backup منتقل شود