nginx HA

HA can be configured in the nodes running Nginx Plus

It implement by running vrrp between the nodes, where the user can specify priority, unicast_src_ip, unicast_peer, and cirtual ipadress.  The node with higher number of priority will run as master. The peer check each other's state by chk_nginx_service.  It returns 0 if the check is succeeds and increate the weight based on the initial priority. It will fail of the timeout is reached (3 sec in the example below)

User can fource the failover by create file under /var/run/keepalived-manual-failvoer.

global_defs {

    vrrp_version 3
}

vrrp_script chk_manual_failover {
    script   "/usr/libexec/keepalived/nginx-ha-manual-failover"
    interval 10
    weight   50
}

vrrp_script chk_nginx_service {
    script   "/usr/libexec/keepalived/nginx-ha-check"
    interval 3
    weight   50
}

vrrp_instance VI_1 {
    interface                  eth0
    priority                   101
    virtual_router_id          51
    advert_int                 1
    accept
    garp_master_refresh        5
    garp_master_refresh_repeat 1
    unicast_src_ip             192.168.100.100

    unicast_peer {
        192.168.100.101
    }

    virtual_ipaddress {
        192.168.100.150
    }

    track_script {
        chk_nginx_service
        chk_manual_failover
    }

    notify "/usr/libexec/keepalived/nginx-ha-notify"    //where to save the log
}