aws_ec2_client_vpn_endpoint dns_servers input does not preserve order

[wenslayer]

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Terraform CLI and Terraform AWS Provider Version

$ terraform -v
Terraform v1.0.5
on darwin_amd64
+ provider registry.terraform.io/hashicorp/aws v3.55.0

Affected Resource(s)

• aws_ec2_client_vpn_endpoint resource

Terraform Configuration Files

Please include all Terraform configurations required to reproduce the bug. Bug reports without a functional reproduction may be closed without investigation.

terraform {
  required_version = "~> 1.0"

  required_providers {
    aws = {
      source  = "hashicorp/aws"
      version = "~> 3.55"
    }
  }
}

provider "aws" {
  region = "us-west-2"
}

resource "aws_ec2_client_vpn_endpoint" "vpn" {
  description = "Test Client VPN Endpoint"

  client_cidr_block      = "172.16.0.0/22"
  server_certificate_arn = "arn:aws:acm:us-west-2:REDACTED:certificate/REDACTED"
  split_tunnel           = true
  transport_protocol     = "udp"

  # Using sample DNS servers for this example, but note the order desired:
  dns_servers = [
    "8.8.8.8",
    "1.1.1.1",
  ]

  authentication_options {
    type                       = "federated-authentication"
    root_certificate_chain_arn = "arn:aws:acm:us-west-2:REDACTED:certificate/REDACTED"
    saml_provider_arn          = "arn:aws:iam::REDACTED:saml-provider/REDACTED"
  }

  connection_log_options {
    enabled               = false
  }
}

Debug Output

TBD

Expected Behavior

Because DNS server order is important (e.g.: we're trying to add an internal and an external DNS server in that order), one should expect the dns_servers input should preserve the order of the elements given (see example above).

Actual Behavior

The dns_servers input appear to be sorted:

$ terraform init && terraform apply
...
Terraform will perform the following actions:

  # aws_ec2_client_vpn_endpoint.vpn will be created
  + resource "aws_ec2_client_vpn_endpoint" "vpn" {
      ...
      + dns_servers            = [
          + "1.1.1.1",
          + "8.8.8.8",
        ]
      ...
    }

Plan: 1 to add, 0 to change, 0 to destroy.
...

$ aws ec2 describe-client-vpn-endpoints --client-vpn-endpoint-ids cvpn-endpoint-REDACTED --query "ClientVpnEndpoints[*].DnsServers[*]"
[
    [
        "1.1.1.1",
        "8.8.8.8"
    ]
]

Steps to Reproduce

1. terraform init && terraform apply

Workaround

1. Manually edit the entries in the AWS Console.

Important Factoids

N/A

References

Source code treats dns_servers input as a set (Type: schema.TypeSet) -- perhaps it should be TypeList instead?

• resource_aws_ec2_client_vpn_endpoint.go lines 40-44

			"dns_servers": {
				Type:     schema.TypeSet,
				Optional: true,
				Elem:     &schema.Schema{Type: schema.TypeString},
			},

[github-actions]

This functionality has been released in v4.0.0 of the Terraform AWS Provider. Please see the Terraform documentation on provider versioning or reach out if you need any assistance upgrading.

For further feature requests or bug reports with this functionality, please create a new GitHub issue following the template. Thank you!

[github-actions]

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 have found a problem that seems similar to this, please open a new issue and complete the issue template so we can capture all the details necessary to investigate further.