This article refers to specifying a domain name, such as ghs.google.com as the backend address of a HTTP(s) port. This feature allows the IP address to be determined based on a DNS query performed during the process of the request for load balancing, geo balancing or ease of integration with third party software.

Limitations

  • Keepalive is ignored, a new connection is created for each client request. It is not possible to keep connections open as the IP the DNS responds to can change at any time.
  • DNS requests can add to the latency of page loads, we cache the DNS result internally for a few seconds however it is important to ensure the Domain Name Server responds reasonably quick and where possible employs a reasonable size cache TTL.
  • Only the first returned "A" record is utilized, there is no load balancing if multiple records are returned.