Configurar LVS con Keepalived. En un anterior articulo ya vimos como instalar un  LVS (Server Load Balancer), hoy le sumamos Keepalived, que es un excelente software de enrutamiento escrito en C.

El objetivo principal de este proyecto es ofrecer instalaciones simples y robustas, que den un equilibrio de carga y alta disponibilidad en infraestructuras Linux.

El equilibrio de carga se basa en un  servidor Linux Virtual Server (IPVS) que nos brinda un balanceo de carga Layer4.

Keepalived implementa un conjunto de comprobadores para mantener y administrar de forma dinámica y adaptativa el grupo de servidores con equilibrio de carga.

Por otro lado con VRRP logramos una alta disponibilidad en el protocolo.

                              |
             + ---------------- + ----------------- +
             | |
 192.168.0.30 | eth0 --- VIP: 192.168.0.29 --- eth0 | 192.168.0.31
     + ------- + -------- + + -------- + ------- +
     | LVS + Keepalived | | LVS + Keepalived |
     + ------- + -------- + + -------- + ------- +
    10.0.0.30 | eth1 ----- VIP: 10.0.0.29 ---- eth1 | 10.0.0.31
             | |
             + ---------------- + ----------------- +
                              |
    + ------------ + | + ------------ +
    | Backend01 | 10.0.0.51 | 10.0.0.52 | Backend02 |
    | Servidor web + ------------ + ------------- + Servidor web |
    | | eth0 eth0 | |
    + ------------ + + ------------ +

Instalar ipvsadm con keepalived

yum -y install ipvsadm

# enable IP forward
echo 'net.ipv4.ip_forward = 1' >> /etc/sysctl.conf 
sysctl -p
touch /etc/sysconfig/ipvsadm 
systemctl start ipvsadm 
systemctl enable ipvsadm

Configurar LVS con Keepalived

mv /etc/keepalived/keepalived.conf /etc/keepalived/keepalived.conf.org 

nano /etc/keepalived/keepalived.conf

# create new
global_defs {
    notification_email {
        root@miservidor.es
    }
    notification_email_from root@miservidor.es
    smtp_server 127.0.0.1
    smtp_connect_timeout 30
    router_id LVS_Server
}
vrrp_instance VI_1 {
    state BACKUP
    # monitored interface
    interface eth0
    # virtual router's ID
    virtual_router_id 51
    # set priority (change this value on each server)
    # (large number means priority is high)
    priority 100
    nopreempt
    # VRRP sending interval
    advert_int 1
    # authentication info between Keepalived servers
    authentication {
        auth_type PASS
        auth_pass password
    }

    virtual_ipaddress {
        # virtual IP address
        192.168.0.29 dev eth0
        10.0.0.29/24 dev eth1
    }
}
virtual_server 192.168.0.29 80 {
    # monitored interval
    delay_loop 3
    # distribution method
    lvs_sched rr
    # routing method
    lvs_method NAT
    protocol TCP

    # backend server#1
    real_server 10.0.0.51 80 {
        weight 1
        HTTP_GET {
            url {
                # monitored path
                path /
                # status code for normally state
                status_code 200
            }
            # timeout(sec)
            connect_timeout 3
        }
    }
    # backend server#2
    real_server 10.0.0.52 80 {
        weight 1
        HTTP_GET {
            url {
                path /
                status_code 200
            }
            connect_timeout 3
        }
    }
}

systemctl start keepalived

systemctl enable keepalived