Azure Front Door configured site is returning "Services not available"

Question

I've got an Azure resource group with two App Service web applications in separate locations deployed and working as expected. I also have a Front Door configuration setup. This is responding as expected when accessed via the azurefd.net address.

I want to add a custom domain to this configuration. First, I created a CNAME in my DNS for a www address.

I then added a simple custom domain configuration (via an ARM template), passing the fully qualified custom domain name as a parameter.

The frontend section looks like this when deployed via the template:

                "frontendEndpoints": [
                {
                    "name": "frontendEndpoint1",
                    "properties": {
                        "hostName": "[concat(parameters('frontDoorName'), '.azurefd.net')]",
                        "sessionAffinityEnabledState": "Enabled",
                        "sessionAffinityTtlSeconds": 0
                    }
                },
                {
                    "name": "frontendEndpoint2",
                    "properties": {
                        "hostName": "[parameters('customDomainName')]",
                        "sessionAffinityEnabledState": "Enabled",
                        "sessionAffinityTtlSeconds": 0
                    }
                }
            ],

The frontend is deployed as expected and I can still access the azurefd.net address.

However, when I try and access the www address, I receive an error in the browser with the message:

Our services aren't available right now. We're working to restore all services as soon as possible. Please check back soon. 0tEdHXAAAAAADUxvBayGtQLDTjRthnz9XTE9OMjFFREdFMDMyMQBFZGdl

I have waited more than half an hour for any DNS changes to roll out, but it still doesn't work.

What could the problem be? What's a easy way of troubleshooting such errors? To be clear, I haven't yet added any HTTPS certificates to this configuration. The web applications do respond to both HTTP and HTTPS, so hopefully that isn't the issue.

Answer 1

This symptom can happen if you have not configured a routing rule for the custom domain that you added as a frontend host. A routing rule needs to be explicitly added for that frontend host, even if one has already been configured for the frontend host under the Front Door subdomain (*.azurefd.net) that your custom domain has a DNS mapping to.

So add a routing rule from the custom domain to the desired backend pool. And wait for several minutes and it will work fine.