Monitor URI

You can use the monitor-uri and monitor fail directives in a frontend section to present a webpage that monitoring software (like Nagios or Icinga) can check periodically to know the state of the load balancer.

Enable the monitoring page Jump to heading #

Below, we enable the monitoring webpage:

haproxy
frontend www
  bind :80
  monitor-uri /checkstatus
  monitor fail if { nbsrv(webservers) eq 0 }
  default_backend webservers
backend webservers
  balance roundrobin
  server server1 10.0.1.3:80 check
  server server2 10.0.1.4:80 check

haproxy
frontend www
  bind :80
  monitor-uri /checkstatus
  monitor fail if { nbsrv(webservers) eq 0 }
  default_backend webservers
backend webservers
  balance roundrobin
  server server1 10.0.1.3:80 check
  server server2 10.0.1.4:80 check

In this example:

• The monitor-uri directive’s value is a URL path that doesn’t map to any resource on your backend servers. The load balancer will respond with an HTTP 200 OK whenever the monitoring software requests this URL path. In this example, we present a page at /checkstatus that monitoring software can request periodically.
• The monitor fail directive returns an HTTP 503 Service Unavailable response if a given condition is true. In this case, the condition checks whether the webservers backend has zero healthy servers up.

See also Jump to heading #

For complete information on the directives used in monitoring, see these topics in the HAProxy Configuration Manual.

• To specify a condition that reports a failure, see monitor fail.
• To define a URI to be used only for monitoring from an external source, see monitor-uri.