Ignore `aiven_transit_gateway_vpc_attachment` `user_peer_network_cidrs` order

supergillis commented 1 year ago

What happened?

The aiven_transit_gateway_vpc_attachment resource expects user_peer_network_cidrs values to be ordered. If the values are equal but in a different order, then the resource will be updated. This means that the Aiven provider will try to update the resource every time Terraform plan runs.

Using the Terraform sort function is not possible as Aiven sorts the values of the CIDR range by their numeric value. For example, Aiven sorts CIDRs like this ["10.7.192.0/18", "10.227.140.0/23"] (7 is numerically smaller than 227) but Terraform sort will sort CIDRs like this ["10.227.140.0/23", "10.7.192.0/18"] (string "227" is smaller than string "7").

Complete example:

# var.cidrs is equal to ["10.227.140.0/23", "10.7.192.0/18"]

resource "aiven_transit_gateway_vpc_attachment" "timescale" {
  vpc_id             = aiven_project_vpc.timescale.id
  peer_cloud_account = data.aws_caller_identity.workload.account_id
  peer_region        = data.aws_region.workload.name
  peer_vpc           = aws_ec2_transit_gateway.main.id

  user_peer_network_cidrs = var.cidrs

  timeouts {
    create = "10m"
  }
}

This results in the following Terraform plan:

Terraform will perform the following actions:

  # aiven_transit_gateway_vpc_attachment.timescale will be updated in-place
  ~ resource "aiven_transit_gateway_vpc_attachment" "timescale" {
        id                      = "xxx/xxx/xxx/xxx/eu-west-1"
      ~ user_peer_network_cidrs = [
          - "10.227.140.0/23",
          - "10.7.192.0/18",
          + "10.7.192.0/18",
          + "10.227.140.0/23",
        ]
        # (6 unchanged attributes hidden)

        # (1 unchanged block hidden)
    }

I'm using the following workaround right now:

  padded_cidrs = [
    for cidr in var.cidrs :
    join("/", [
      for part in split("/", cidr) :
      join(".", [for num in split(".", part) : format("%03s", num)])
    ])
  ]
  sorted_padded_cidrs = sort(local.padded_cidrs)
  sorted_cidrs = [
    for padded_cidr in local.sorted_padded_cidrs :
    join("/", [
      for part in split("/", padded_cidr) :
      join(".", [for num in split(".", part) : replace(num, "/^0*([\\d]+)/", "$1")])
    ])
  ]
}

What did you expect to happen?

The aiven_transit_gateway_vpc_attachment resource should not update user_peer_network_cidrsif the set of values equals the actual values. It should ignore the order of the values.