docs/data/reusables/enterprise_installation/monitoring-replicas.md

You can monitor the availability of {% data variables.product.prodname_ghe_server %} by checking the status code that is returned for the https://HOSTNAME/status URL. An appliance that can service user traffic will return status code 200 (OK). An appliance may return 503 (Service Unavailable) for this URL and other web or API requests for a few reasons:

• The appliance is a passive replica, such as the replica in a two-node high availability configuration.
• The appliance is in maintenance mode.
• The appliance is part of a geo-replication configuration, but is an inactive replica.

You can also use the Replication overview dashboard available at:

https://HOSTNAME/setup/replication