Value of 'count' cannot be computed

[jdb1441]

Hello,

It appears that the changes made to the output file from commit "Make use of name_prefix optional (#74)" is causing errors when we try to run a plan with security groups referencing an ingress with source security group id. We receive the following error for each security group:

• module.subnet_name.aws_security_group_rule.ingress_with_source_security_group_id: aws_security_group_rule.ingress_with_source_security_group_id: value of 'count' cannot be computed

I have traced this back to the following change in the output file:
Original working code:

output "this_security_group_id" {
  description = "The ID of the security group"
  value       = "${element(concat(aws_security_group.this.*.id, list("")), 0)}"
}

Updated broken code:

output "this_security_group_id" {
  description = "The ID of the security group"
  value       = "${element(concat(coalescelist(aws_security_group.this.*.id, aws_security_group.this_name_prefix.*.id), list("")), 0)}"
}

We are running on tf version v0.11.2, but coalescelist was introduced in v0.9.4 so that shouldn't be a problem. Please let me know if there is any additional information you would like.

[antonbabenko]

You should specify computed_ingress_with_source_security_group_id instead of ingress_with_source_security_group_id argument and set number_of_computed_ingress_with_source_security_group_id when referencing computed values (values from the module).

See this example:

terraform-aws-security-group/examples/computed/main.tf

Lines 46 to 53 in 3ce6160

	computed_ingress_with_source_security_group_id = [
	{
	rule = "mysql-tcp"
	source_security_group_id = "${module.http_sg.this_security_group_id}"
	},
	]
	number_of_computed_ingress_with_source_security_group_id = 1

Could you show the code how you invoke this module, I don't understand why output is not working for you.

[jdb1441]

Hi Anton,

Here is an example of how I am invoking it that works fine with the old version of the output and fails with the new:

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

  name        = "${var.environment}-example"
  description = "Security group for example"
  vpc_id      = "${module.vpc.vpc_id}"

  ingress_with_cidr_blocks = [
    {
      from_port   = 22
      to_port     = 22
      protocol    = "tcp"
      description = "default ssh port"
      cidr_blocks = "1.2.3.4/32"
    },
  ]

  ingress_with_source_security_group_id = [
    {
      from_port                = 22
      to_port                  = 22
      protocol                 = "tcp"
      description              = "SSH"
      source_security_group_id = "${module.other_example_sg.this_security_group_id}"
    }
  ]

  egress_rules = ["all-all"]
}

[jdb1441]

Hey @antonbabenko ,

Any idea on why this is happening? This is causing significant problems so we will likely be moving to our own module with the previous code if we can't get this resolved soon.

Thanks!
Josh

[antonbabenko]

As I have pointed out in the previous comment, you need to specify configuration inside computed_ingress_with_source_security_group_id instead of ingress_with_source_security_group_id if you are using values from modules.

Also add number_of_computed_ingress_with_source_security_group_id = 1.

[antonbabenko]

Closing this issue.

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