DNS Mystery in Heroku CNAME Redirection

Question

I have something quite mysteriously not working in my DNS configuration :

• My app is at : http://my-domain.herokuapp.com

• I configured my-domain.com the following way :

  @ 10800 IN A 174.129.25.170
  www 10800 IN CNAME my-domain.herokuapp.com.
  

using wwwizer.

So, http://my-domain.com redirects to http://www.my-domain.com which CNAMEs to http://my-domain.herokuapp.com

Everything seems fine, but when I enter http://my-domain.com or http://www.my-domain.com, I get : Heroku | No such app error message.

So I tried this :

host http://www.my-domain.com
www.my-domain.com is an alias for my-domain.herokuapp.com.
my-domain.herokuapp.com has address 54.243.92.108

and

host http://my-domain.herokuapp.com
my-domain.herokuapp.com has address 184.72.248.52

I can't see where the problem is. WWWizer seems working fine, but it feels like CNAME hasn't refreshed since the herokuapp IP changed ...

Any tip would be super appreciated.

Thanks

Answer 1

Thanks to @neil-middleton comment, I found the solution.

I did added earlier heroku domains:add my-domain.com

but did not for heroku domains:add www.my-domain.com

which is the one that matters here. (Though I left both in case)

So it seems heroku has its own internal DNS control when CNAME-ing *.herokuapp.com where it gets as an entry the heroku domains.

This is logical to avoid setting CNAME to an app one don't own.