Error updating Autoscaling group: minimum field size of 1, UpdateAutoScalingGroupInput.VPCZoneIdentifier

[hashibot]

This issue was originally opened by @brikis98 as hashicorp/terraform#12150. It was migrated here as part of the provider split. The original body of the issue is below.

---

Terraform Version

Terraform v0.8.6

Affected Resource(s)

• aws_autoscaling_group

Terraform Configuration Files

In a module, I have the following:

resource "aws_autoscaling_group" "autoscaling_group" {
  launch_configuration = "${aws_launch_configuration.launch_configuration.name}"

  availability_zones  = ["${var.availability_zones}"]
  vpc_zone_identifier = ["${var.subnet_ids}"]

  min_size             = 3
  max_size             = 3
  desired_capacity     = 3
}

variable "availability_zones" {
  type = "list"
  default = []
}

variable "subnet_ids" {
  type = "list"
  default = []
}

My usage of the module looks something like this:

module "foo" {
  source = "modules/foo"

  availability_zones = ["${data.aws_availability_zones.all.names}"]
}

data "aws_availability_zones" "all" {}

Expected Behavior

1. I should be able to run terraform apply without errors.
2. I should be able to run terraform plan after the initial apply and see no changes.

Actual Behavior

1. I am able to run terraform apply without errors.

2. When I run terraform plan, I see the following diff, even though I haven't changed anything:

   ~ module.consul.aws_autoscaling_group.autoscaling_group
       vpc_zone_identifier.#: "1" => "0"
       vpc_zone_identifier.0: "" => ""
   

   Even worse, if I run terraform apply now, I get an error:

   * aws_autoscaling_group.autoscaling_group: Error updating Autoscaling group: InvalidParameter: 1 validation error(s) found.
   - minimum field size of 1, UpdateAutoScalingGroupInput.VPCZoneIdentifier.
   

This makes it impossible to apply any further changes.

Steps to Reproduce

1. terraform apply
2. terraform plan
3. terraform apply

References

• VPCZoneIdentifier cannot be empty terraform#6417 looks similar.

[github-actions]

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[ghost]

I'm going to lock this issue because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active issues.

If you feel this issue should be reopened, we encourage creating a new issue linking back to this one for added context. Thanks!