I have my base app hosted in GCP App Engine.
The base domain for this app is app.xyz.com
I have user based subdomain dashboard access.
Eg. User 1 can have their subdomain xyz.pqr.com
and then map it to my base domain
app.xyz.com
User 2 can have their subdomain example2.com
and then map it to my base domain
app.xyz.com
I want the mapping to be done through CNAME only. i.e User have to change the cname to map with my base domain.
However while visiting these subdomain its landing me to google 404 page.
I want App engine to serve content to my base domain and all domain mapped to it.
In app engine, I have added *.xyz.com as domain mapping with traffic proxied through cloudflare using origin server ssl certificate.
Currently i can access the app through any subdomain like v1.xyz.com
or v2.xyz.com
buy not through v1.abc.com
Which is currently mapped to app.xyz.com through cname
current ssl settings for Cloudflare in Full mode
Finally fixed it using a https load balancer:
Backend -> App Engine Instance
Frontend -> app.xyz.com
v1.abc.com
-> app.xyz.com
via CNAME