health_check_listen

Specifies the port on which the server is to listen for health check requests. 

health_check_listen = http://servername:port
For example: 
health_check_listen = http://machine1:7220

When using localhost as the servername, the listen will only be accessible from the local machine. If you omit the servername, the listen will behave similarly to setting localhost in the server listen parameter.

For example: 
health_check_listen = http://:7220

You can use an IP address instead of hostname.

For example: 
health_check_listen = http://192.168.10.107:7220

When specifying an IPv6 address, use square brackets around the address specification.

For example: 
health_check_listen = http://[2001:cafe::107]:7220

You can use only one health_check_listen entry at a time. For more information, see Server Health.