Terraform: list to string

Question

I am trying to create a Security Group using terraform module terraform-aws-modules/security-group/aws. This would need VPC id which is taken from aws_vpcs data source. The VPC id requires a string value, but the aws_vpcs data source returns a list with a single value.

Please find

data "aws_vpcs" "this" {
  tags = {
    "Name" = "example"
  }
}

module "route53_sg" {
  source = "terraform-aws-modules/security-group/aws"

  name        = "R53_health_checkers"
  description = "Security group for Route53 health checkers"
  vpc_id      = element([data.aws_vpcs.this.ids], 0)
  ingress_cidr_blocks = [
...
...
...
  ]
  ingress_rules = ["https-443-tcp"]
}

$ terraform apply
data.aws_lb.ext_alb: Refreshing state...
data.aws_vpcs.this: Refreshing state...

Error: Invalid value for module argument

  on main.tf line 75, in module "route53_sg":
  75:   vpc_id      = element([data.aws_vpcs.this.ids], 0)

The given value is not suitable for child module variable "vpc_id" defined at
.terraform/modules/route53_sg/terraform-aws-modules-terraform-aws-security-group-d55e4de/variables.tf:10,1-18:
string required.



vpc_id is expecting a Single string. FOLLOWING is a result from Output.tf

$ terraform apply
data.aws_lb.ext_alb: Refreshing state...
data.aws_vpcs.this: Refreshing state...

Apply complete! Resources: 0 added, 0 changed, 0 destroyed.

Outputs:

vpc = [
  "vpc-08067a598522a7b30",
]

Jackyjjc · Accepted Answer · 2019-08-12 06:29:19Z

5

data.aws_vpcs.this.ids is already a list, you don't need to put it into another list.

Try:

vpc_id = element(data.aws_vpcs.this.ids, 0)

EDIT: Answering questions from the comment: It seems like the ids returned is a set instead of a list, as mentioned in a similar issue here: https://github.com/terraform-providers/terraform-provider-aws/issues/7522

If you are using 0.12.x: You can do

vpc_id = element(tolist(data.aws_vpcs.this.ids), 0)

If you are using 0.11.x: You can do

vpc_id = element(split(",", join(",", data.aws_vpcs.this.ids))), 0)

edited Aug 12, 2019 at 6:29

answered Aug 12, 2019 at 6:07

Jackyjjc

5521 gold badge3 silver badges13 bronze badges

Sign up to request clarification or add additional context in comments.

4 Comments

Tony Mathew Thomas Over a year ago

Thanks Jackyjjc for your reply I tried that. Got the following error : ``` Error: Error in function call on main.tf line 75, in module "route53_sg": 75: vpc_id = element(data.aws_vpcs.this.ids, 0) |---------------- | data.aws_vpcs.this.ids is set of string with 1 element Call to function "element" failed: cannot read elements from set of string. ```

Jackyjjc Over a year ago

I have edited the answer to include the answer to your question

Tony Mathew Thomas Over a year ago

vpc_id = element(tolist(data.aws_vpcs.this.ids), 0) helped. Thank you

Martin Atkins Over a year ago

I'd suggest using sort(data.aws_vpcs.this.ids)[0] instead here... the result should be the same, but sort makes it explicit that you want to take the first element sorted lexically (though with a single-element set it doesn't really matter) and using the element function to access list elements is deprecated in favor of the explicit list index syntax.

Collectives™ on Stack Overflow

Terraform: list to string

1 Answer 1

4 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

4 Comments

Your Answer

Sign up or log in

Post as a guest

Related