如何将 Route53 别名添加到现有 Route53 条目？

Question

I have a DNS entry already in Route 53. In my CDK stack, I want to set up an alias (effectively a CNAME), so I have a new DNS entry pointing to the existing one. For example, I want to make new.example.com point to existing.example.com , where example.com is hosted in Route 53 and existing is already set up and working.

Through the AWS console I would just create a new A or CNAME record for new.example.com and set it as an alias of existing.example.com and it would be fine, so I am trying to replicate this in CDK.

In the CDK docs , it says I can do this:

declare const zone: route53.HostedZone;
declare const record: route53.ARecord;
new route53.ARecord(this, 'AliasRecord', {
  zone,
  target: route53.RecordTarget.fromAlias(new targets.Route53RecordTarget(record)),
});

However, the docs don't say how to populate the record variable.

If I look at the route53.ARecord docs , there doesn't appear to be a way to look up an existing record.

The closest I could find is using one of the other RecordSet.fromXXX() functions instead of fromAlias , however there doesn't appear to be one that can look up host names:

...
target: cdkRoute53.RecordTarget.fromValues('target.example.com'), // doesn't work

Unfortunately, RecordTarget.fromValues() only accepts an IP address. If you put a hostname in, it tells you:

Invalid Resource Record: 'FATAL problem: ARRDATAIllegalIPv4Address (Value is not a valid IPv4 address) encountered with 'target.example.com'

So it looks like I can only create the alias if I also created the target records in the same stack - there doesn't appear to be a way to load an existing record, so you can pass it in as the target for the new alias.

What am I missing?

Answer 1

I found a workaround in the meantime thanks to this answer . Since then they added the functionality that was missing, but it looks like they didn't provide lookups so that workaround still applies.

The solution is to provide a bind() function instead that provides the necessary information:

const route53entry = new cdkRoute53.ARecord(this, 'dns', {
  recordName: 'new.example.com',
  zone: hostedZone,
  target: cdkRoute53.RecordTarget.fromAlias({
    bind: () => ({
      dnsName: 'existing.example.com',
      hostedZoneId: hostedZone.hostedZoneId,
    }),
  }),
});