Can't test alternate CDN for assets domain in staging?

[sengi]

Seems there was some confusion around how assets.staging.publishing.service.gov.uk is set up in regard to testing switching between the main (Fastly) and alternative (AWS CloudFront) CDNs.

We should be able to test the assets domain on the alt CDN. Might already be fine and there was just confusion about how to do it, or maybe there's something to fix/improve about the way it's set up.

Moved from https://trello.com/c/vXZ5WQNd.

[sengi]

Not sure what prompted the claim that assets.staging.publishing.service.gov.uk points at prod, but it doesn't appear to be true.

dig +short assets.staging.publishing.service.gov.uk

www-gov-uk.map.fastly.net.
151.101.60.144

Staging Assets service in Fastly has the assets.staging.publishing.service.gov.uk domain. Here's the relevant snippet of VCL from the active version of that service's config:

backend F_awsorigin {
...
    .host = "assets-origin.eks.staging.govuk.digital";
...
}

backend F_mirrorS3 {
...
    .host = "govuk-staging-mirror.s3-eu-west-2.amazonaws.com";
...
}

[sengi]

The playbook for testing switchover already covers assets.staging.publishing.service.gov.uk so I think we're done here.