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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