data google_dns_managed_zone errors if zone doesn't exist

[jimsnab]

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Terraform Version

Terraform v1.0.4
on linux_amd64
+ provider registry.terraform.io/hashicorp/google v3.77.0
+ provider registry.terraform.io/hashicorp/helm v2.2.0
+ provider registry.terraform.io/hashicorp/kubernetes v2.4.0

Affected Resource(s)

• data source google_dns_managed_zone

Terraform Configuration Files

# External DNS zone
data "google_dns_managed_zone" "external_zone" {
  name        = local.zone_name
  project     = var.project_id 
}

resource "google_dns_managed_zone" "external_zone" {
  count       = (data.google_dns_managed_zone.external_zone.dns_name == null ? 1 : 0)
  dns_name    = "${var.project_name}.${var.domain_name}"
  name        = local.zone_name
  description = "External DNS zone"
}

Debug Output

Panic Output

Expected Behavior

Script creates the zone first time it is run, and does not attempt to create the zone subsequent runs - each run starting from a fresh tfstate file.

Since Terraform lacks a create-if-necessary mechanism, the count is typically used as a workaround. The Google provider is inconsistent in its support for this workaround. For example, data google_kms_key_ring will have its output attributes null if the key ring doesn't exist (and will not error).

google_dns_managed_zone should provide a way to specify the zone should be created if it does not yet exist.

Actual Behavior

The script errors the first time because data google_dns_managed_zone does not support returning nulls as output.

Steps to Reproduce

1. terraform apply

Important Factoids

This is normally not needed if terraform tfstate file is maintained. However, due to other bugs, we are blocked use terraform destroy, and thus sometimes we need to start a new state file with an environment that has some existing configuration. And therefore we require a way to create-if-missing.

terraform import is a manual and laborious workaround, but does not always work either due to errors for missing dependencies such as providers that haven't yet been established (catch-22).

References

• #0000

[github-actions]

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