module requires two phase apply due to value of count cannot be computed

[joshmyers]

what

While trying to test a new module, which depends on this one, I added example usage:

module "vpc" {
  source    = "git::https://github.com/cloudposse/terraform-aws-vpc.git?ref=master"
  namespace = "example"
  stage     = "dev"
  name      = "app"
}

resource "aws_route53_zone" "default" {
  name = "cp-example.com"
}

module "subnets" {
  source             = "git::https://github.com/cloudposse/terraform-aws-dynamic-subnets.git?ref=master"
  namespace          = "example"
  stage              = "dev"
  name               = "app"
  region             = "us-east-1"
  vpc_id             = "${module.vpc.vpc_id}"
  igw_id             = "${module.vpc.igw_id}"
  cidr_block         = "10.0.0.0/16"
  availability_zones = ["us-east-1a", "us-east-1b"]
}

module "elasticsearch" {
  source                  = "git::https://github.com/cloudposse/terraform-aws-elasticsearch.git?ref=tags/0.1.5"
  namespace               = "example"
  stage                   = "dev"
  name                    = "es"
  dns_zone_id             = "${aws_route53_zone.default.id}"
  security_groups         = []
  vpc_id                  = "${module.vpc.vpc_id}"
  subnet_ids              = ["${module.subnets.public_subnet_ids}"]
  zone_awareness_enabled  = "true"
  elasticsearch_version   = "6.2"
  instance_type           = "t2.small.elasticsearch"
  instance_count          = 4
  kibana_subdomain_name   = "example-kibana-es"
  encrypt_at_rest_enabled = "false"
  ebs_volume_size         = 10
  iam_actions             = ["es:*"]
  iam_role_arns           = ["*"]
}

module "elasticsearch-cleanup" {
  source               = "../"
  es_endpoint          = "${module.elasticsearch.domain_endpoint}"
  es_domain_arn        = "${module.elasticsearch.domain_arn}"
  es_security_group_id = "${module.elasticsearch.security_group_id}"
  vpc_id               = "${module.vpc.vpc_id}"
  enabled              = "true"
  namespace            = "example"
  stage                = "dev"
  schedule             = "rate(5 minutes)"
}

which failed with the below error:

Error: Error running plan: 2 error(s) occurred:

* module.elasticsearch.module.domain_hostname.aws_route53_record.default: aws_route53_record.default: value of 'count' cannot be computed
* module.elasticsearch.module.kibana_hostname.aws_route53_record.default: aws_route53_record.default: value of 'count' cannot be computed

This happens because the ID cannot be computed until after creation.
The workaround for this was using a two stage apply and passing the -target option.

[tthayer]

@joshmyers I know this is an old issue but the workaround described here would allow you to complete this in one pass:
hashicorp/terraform#1178 (comment)

[Gowiem]

I'm still running into this issue even with Terraform 0.13 and Module depends_on. I've posted about this over in the SweetOps Slack to see if I can get to the bottom of it.