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Ruby

Posted by Jiaming Zhang
Jiaming Zhang
10,170 Points

Is there a way to find out the CNAME value of a certain domain?

Here is the context:

I am providing a service via the following URL: http://api.example.com/ ...... rest of the url ......

Assume there is a service consumer who wants to use this service but they want to have a custom domain http://api.consumer.com/ ...... rest of the url ......

The consumer will be asked to set the CNAME value of http://api.consumer.com/ to http://api.example.com/ so my service can handle all the requests originally sent to http://api.consumer.com/.

I am wondering how to find out whether the consumer has properly set the CNAME value, preferably through a Ruby package. Thanks.

1 Answer

Geoff Parsons
Geoff Parsons
11,679 Points

You can always use the UNIX dig command and parse the results. For example you would use dig example.com any and look for instances of "CNAME". But that's clunky and forces system dependencies in your code.

I found a library that will get you what you want, but it's not the most user-friendly API. Check out dnsruby (rdoc). Here's a rough example of what i think you're looking for:

require 'dnsruby'

resolver = Dnsruby::Resolver.new
response = resolver.query('www.youtube.com', Dnsruby::Types.CNAME)
response.answer.any? { |answer| answer.name.to_s == 'www.youtube.com' }    # => true
response.answer.any? { |answer| answer.name.to_s == 'www.yahoo.com' }        # => false

Hope that gets you on the right track.