added new interpolation function uuidv5

[lscheidler]

it would be nice, if this interpolation function could be added, so it can be used in different use cases.

My use-case for this function is, that it will be used in aws_route53_record resources, so that the sub-domain isn't easily guessed, but anyone knowing the dns name can convert it back to plain text.

resource "aws_route53_record" "client-name-or-domain" {
  zone_id = "${aws_route53_zone.primary.zone_id}"
  name    = "${uuidv5("dns", "client-name-or-domain")}.example.com"
  type    = "A"
  ttl     = "300"
  records = ["${aws_eip.lb.public_ip}"]
}

[hashicorp-cla]

All committers have signed the CLA.

[apparentlymart]

Hi @lscheidler! Thanks for working on this.

This seems like a reasonable idea to me, and I'd like to include it. There are unfortuantely a few details we'll need to deal with first though...

Firstly, the v0.11 branch is closed to outside contributions and used for maintenance patch releases only -- primarily backports. Please instead target your change at the master branch for inclusion in a future release. (v0.11 is in maintenance mode now, so no new features will be added to it.)

Secondly, the config/interpolation_funcs.go file is now dead code and will be removed in the near future. Functions are developed instead in the lang/funcs package, where you can find the new implementation of uuid as an example. The new functions mechanism is a little different than the old but for this function in particular (where the inputs and outputs are all just strings) it shouldn't look too different than your implementation in the old way.

Finally, functions now have their own documentation pages, allowing us to give more details on their functionality and show examples of usage. They must also be listed in the nativation so that they can be found. Again, the uuid function is a reasonable template to follow for these.

The uuid function in the master branch (for v0.12 and later) is marked as "impure" because its result will vary across multiple calls for the same input. However, v5 UUIDs depend only on the given namespace and name, so that constraint doesn't apply there: we can leave uuidv5 as a pure function (the default) and thus allow it to be evaluated immediately during plan time, rather than deferred to apply time.

Thanks again for working on this! If you need any help with the above, please do let me know. The master branch is currently feature-frozen until we complete the v0.12.0 release, but we'll look at getting this merged in once the initial v0.12 release is closed.

[lscheidler]

Hi @apparentlymart . Thanks for Your input. I am going to create a new pull request on master branch and try to implement it in the lang/funcs package.

[ghost]

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