Is it possible to move a hostname between two Azure Front Door resources without downtime?

Question

TL;DR:

Can I move hostnames between Azure Front Door resources within the same subscription without an outage?

Context

I have four Frontdoor resources - each with a set of hostnames. My organisation is looking to consolidate these hostnames to a single Front Door resource, to lower costs and reduce complexity.

I've written the rewritten the ARM templates in Bicep, and then followed this tutorial to deploy the resource, hoping that it would allow me to prepare the hostnames and routing rules on the newly created Frontdoor before modifying the permanent DNS records.

Unfortunately I'm presented with the below error message:

Steps followed:

I've followed these steps both deploying through portal, and with individual Bicep deployments, with the same result.

• Create Front Door resource
• Create CNAME record with DNS provider:
  • afdverify.www.contoso.com ➡ afdverify.contoso-frontend.azurefd.net
• Edit resource:
  • Add and validate www.contoso.com as a custom hostname on the resource
  • Add backend pools and routing rules
• Press Save, which is unsuccessful with the presenting the attached error message

Thanks in advance for any help or time spent on the issue

Answer 1

A direct domain move between unrelated Azure Front Door instances currently requires downtime. You can evade the downtime only when migrating the whole Front Door to a higher tier: Classic to Standard/Premium or Standard to Premium.

It may be possible to move the domain without downtime indirectly, in two separate zero-downtime moves, though. As the intermediate target of the domain, you can use a third-party CDN, one of the origins (backends in the Classic terminology), or any other service capable of providing the required functionality and handling the load at least for the duration of the migration.

Hopefully, Microsoft will introduce the functionality required for the direct zero-downtime migration someday.

Answer 2

The steps you were following helps in adding custom domain to your Front Door that has been configured with CNAME to external registers like GoDaddy. As Front Door is globally available, there should be unique frontend host name across servers else it would result in a host name conflict.

I've confirmed with the Azure Front Door Product Group team and they confirmed that it is not possible to move a hostname between two Azure Front Door resources without downtime. The custom domains need to be removed from the original front Door and added to the new one.