Using template output fails because of unknown value

[dalehamel]

I am using the output of a template to get a dns record value.

When I try to change the count on that template, it will put the unknown value in the diff:

 module.chef_instance.aws_route53_record.srvrecord
    records.#:          "2" => "3"
    records.1158792681: "0 0 80 srvtest1.test.us-east-1.shopifyvpc.com" => "0 0 80 srvtest1.test.us-east-1.shopifyvpc.com"
    records.1274424632: "0 0 80 srvtest0.test.us-east-1.shopifyvpc.com" => "0 0 80 srvtest0.test.us-east-1.shopifyvpc.com"
    records.2068225513: "" => "0 0 80 74D93920-ED26-11E3-AC10-0800200C9A66"

This then fails to apply with the message:

* aws_route53_record.srvrecord: diffs didn't match during apply. This is a bug with Terraform and should be reported.

Now that the value is known, because the template resource actually exists, if I run a plan:

~ module.chef_instance.aws_route53_record.srvrecord
    records.#:          "2" => "3"
    records.1158792681: "0 0 80 srvtest1.test.us-east-1.shopifyvpc.com" => "0 0 80 srvtest1.test.us-east-1.shopifyvpc.com"
    records.1274424632: "0 0 80 srvtest0.test.us-east-1.shopifyvpc.com" => "0 0 80 srvtest0.test.us-east-1.shopifyvpc.com"
    records.1446640794: "" => "0 0 80 srvtest2.test.us-east-1.shopifyvpc.com"

It's able to actually GET the value, and it actually applies.

@phinze any idea how this can be fixed? Maybe we just need to teach the 'apply diffs must match' check resolve unknown values rather than crying?

[dalehamel]

@thegedge theorizes this because route53 uses 'TypeSet' instead of 'TypeList'

[mitchellh]

Hey @dalehamel. Thanks! Can you give us a sample TF config that triggers this? Thanks!

[dalehamel]

@mitchellh this is the most minimal example I could produce

provider "aws" {
  region = "us-east-1"
}

variable "instances" {
  default = 2
}

resource "template_file" "node_name" {
  count = "${var.instances}"
  filename = "${path.module}/template.tpl"
  vars {
    index = "${count.index}"
  }
}

resource "aws_route53_zone" "dev" {
  name = "example.com"

  tags {
    Environment = "dev"
  }
}

resource "aws_route53_record" "srvrecord" {
  count = "${var.instances}"
  zone_id = "${aws_route53_zone.dev.id}"
  name = "foo.example.com"
  type = "SRV"
  ttl = "1"
  records = ["${formatlist("0 0 %s", template_file.node_name.*.rendered)}"]
}

it generates a plan like this:

+ aws_route53_record.srvrecord.0
    fqdn:               "" => "<computed>"
    name:               "" => "foo.example.com"
    records.#:          "" => "1"
    records.1485628133: "" => "0 0 74D93920-ED26-11E3-AC10-0800200C9A66"
    ttl:                "" => "1"
    type:               "" => "SRV"
    zone_id:            "" => "${aws_route53_zone.dev.id}"

+ aws_route53_record.srvrecord.1
    fqdn:               "" => "<computed>"
    name:               "" => "foo.example.com"
    records.#:          "" => "1"
    records.1485628133: "" => "0 0 74D93920-ED26-11E3-AC10-0800200C9A66"
    ttl:                "" => "1"
    type:               "" => "SRV"
    zone_id:            "" => "${aws_route53_zone.dev.id}"

+ aws_route53_zone.dev
    comment:          "" => "Managed by Terraform"
    name:             "" => "examplec.om"
    name_servers.#:   "" => "<computed>"
    tags.#:           "" => "1"
    tags.Environment: "" => "dev"
    vpc_region:       "" => "<computed>"
    zone_id:          "" => "<computed>"

+ template_file.node_name.0
    filename:   "" => "template.tpl"
    rendered:   "" => "<computed>"
    vars.#:     "" => "1"
    vars.index: "" => "0"

+ template_file.node_name.1
    filename:   "" => "template.tpl"
    rendered:   "" => "<computed>"
    vars.#:     "" => "1"
    vars.index: "" => "1"

Notice how the records all have the "unknown value" of 74D93920-ED26-11E3-AC10-0800200C9A66? This will cause the diff sanity check to fail.

cc @phinze @thegedge

[mitchellh]

Got it, thanks @dalehamel

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