A.3. Install and Configure keepalived

Perform the following procedure on your two HAProxy nodes:
  1. Install keepalived. 
    # yum install -y keepalived
  2. Configure keepalived. 
    # vim /etc/keepalived/keepalived.conf
    In the following configuration, there is a script to check the HAProxy processes. The instance uses eth0 as the network interface and configures haproxy as the master server and haproxy2 as the backup server. It also assigns a virtual IP address of 192.168.0.100. 
    vrrp_script chk_haproxy {
  script "killall -0 haproxy" # check the haproxy process
  interval 2 # every 2 seconds
  weight 2 # add 2 points if OK
}

vrrp_instance VI_1 {
  interface eth0 # interface to monitor
  state MASTER # MASTER on haproxy, BACKUP on haproxy2
  virtual_router_id 51
  priority 101 # 101 on haproxy, 100 on haproxy2
  virtual_ipaddress {
    192.168.0.100 # virtual ip address
  }
  track_script {
    chk_haproxy
  }
}
  3. Enable and start keepalived. 
    # systemctl enable keepalived
# systemctl start keepalived