dns-delegated

This component provisions a delegated DNS zone for managing subdomains delegated from a primary DNS account. The primary DNS zone must already exist via the dns-primary component. Use dns-delegated when you need a subdomain (e.g. prod.example.com) managed in a different account from the primary root zone (e.g. example.com).

If you are deploying a root zone (e.g. example.com) and only a single account needs to manage or update the zone, use the dns-primary component instead. See “Why not use dns-delegated for all vanity domains?” for details.

This component also provisions a wildcard ACM certificate for the delegated subdomain. Deploy it globally (once per account) rather than regionally; see “Why should the dns-delegated component be deployed globally rather than regionally?” for rationale.

Note: After delegating a subdomain (e.g. prod.example.com) to an account, that account can create deeper subdomains (e.g. api.use1.prod.example.com) without additional delegation, but additional TLS certificates may be required because a wildcard certificate only matches a single level. Use the acm component for additional certs.

Limitations

Switching a hosted zone from public to private can cause issues because the provider will try to perform an update instead of a ForceNew. It is not possible to toggle between public and private. If changing from public to private and downtime is acceptable, delete records and the hosted zone, destroy the Terraform component, and re-deploy with new settings.

If downtime is acceptable (workaround):

1. Delete anything using ACMs connected to previous hosted zones
2. Delete ACMs
3. Delete entries in the public hosted zone
4. Delete the hosted zone
5. Use atmos to destroy dns-delegated to remove the public hosted zone
6. Use atmos to deploy dns-delegated for the private hosted zone
7. Re-deploy dependent components (aurora-postgres, msk, external-dns, echo-server, etc.) to the new hosted zone

If downtime is not acceptable (workaround):

1. Create a new virtual component of dns-delegated with the correct private inputs
2. Deploy the new dns-delegated-private component
3. Re-deploy dependent components to the new hosted zone

Caveats

• Do not create an NS delegation for a subdomain within a zone that is not authoritative for that subdomain (e.g. if a parent subdomain is already delegated). Route 53 Public DNS allows conflicting delegations, which can cause inconsistent resolution depending on the resolver’s strategy (see RFC7816 “QName Minimization”). Verify proper resolution with multiple resolvers (e.g. 8.8.8.8 and 1.1.1.1).

Usage

Stack Level: Global

Use this component in global stacks for any accounts where you host services that need DNS records on a delegated subdomain of the root domain.

Public hosted zone example: devplatform.example.net is created and the example.net zone in the primary DNS account contains a record delegating DNS to the new hosted zone. This also creates an ACM record.

components:
  terraform:
    dns-delegated:
      vars:
        zone_config:
          - subdomain: devplatform
            zone_name: example.net
        request_acm_certificate: true
        dns_private_zone_enabled: false
        #  dns_soa_config configures the SOA record for the zone::
        #    - awsdns-hostmaster.amazon.com. ; AWS default value for administrator email address
        #    - 1 ; serial number, not used by AWS
        #    - 7200 ; refresh time in seconds for secondary DNS servers to refresh SOA record
        #    - 900 ; retry time in seconds for secondary DNS servers to retry failed SOA record update
        #    - 1209600 ; expire time in seconds (1209600 is 2 weeks) for secondary DNS servers to remove SOA record if they cannot refresh it
        #    - 60 ; nxdomain TTL, or time in seconds for secondary DNS servers to cache negative responses
        #    See SOA Record Documentation for more information.
        dns_soa_config: "awsdns-hostmaster.amazon.com. 1 7200 900 1209600 60"

Private hosted zone example: devplatform.example.net is created and the example.net zone in the primary DNS account contains a record delegating DNS to the new hosted zone. This creates an ACM record using a Private CA.

components:
  terraform:
    dns-delegated:
      vars:
        zone_config:
          - subdomain: devplatform
            zone_name: example.net
        request_acm_certificate: true
        dns_private_zone_enabled: true
        vpc_region_abbreviation_type: short
        vpc_primary_environment_name: use2
        certificate_authority_component_name: private-ca-subordinate
        certificate_authority_stage_name: pca
        certificate_authority_environment_name: use2
        certificate_authority_component_key: subordinate

Variables

Required Variables

region (string) required

AWS Region

zone_config required

Zone config

Type:

list(object({
subdomain = string
zone_name = string
}))

Optional Variables

aws_shield_protection_enabled (bool) optional

Enable or disable AWS Shield Advanced protection for Route53 Zones. If set to 'true', a subscription to AWS Shield Advanced must exist in this account.

Default value: false

certificate_authority_component_key (string) optional

Use this component key e.g. root or mgmt to read from the remote state to get the certificate_authority_arn if using an authority type of SUBORDINATE

Default value: null

certificate_authority_component_name (string) optional

Use this component name to read from the remote state to get the certificate_authority_arn if using an authority type of SUBORDINATE

Default value: null

certificate_authority_enabled (bool) optional

Whether to use the certificate authority or not

Default value: false

certificate_authority_environment_name (string) optional

Use this environment name to read from the remote state to get the certificate_authority_arn if using an authority type of SUBORDINATE

Default value: null

certificate_authority_stage_name (string) optional

Use this stage name to read from the remote state to get the certificate_authority_arn if using an authority type of SUBORDINATE

Default value: null

dns_private_zone_enabled (bool) optional

Whether to set the zone to public or private

Default value: false

dns_soa_config (string) optional

Root domain name DNS SOA record:

• awsdns-hostmaster.amazon.com. ; AWS default value for administrator email address
  
• 1 ; serial number, not used by AWS
  
• 7200 ; refresh time in seconds for secondary DNS servers to refresh SOA record
  
• 900 ; retry time in seconds for secondary DNS servers to retry failed SOA record update
  
• 1209600 ; expire time in seconds (1209600 is 2 weeks) for secondary DNS servers to remove SOA record if they cannot refresh it
  
• 60 ; nxdomain TTL, or time in seconds for secondary DNS servers to cache negative responses
  See SOA Record Documentation for more information.
  

Default value: "awsdns-hostmaster.amazon.com. 1 7200 900 1209600 60"

request_acm_certificate (bool) optional

Whether or not to create an ACM certificate

Default value: true

vpc_component_name (string) optional

The name of a VPC component

Default value: "vpc"

vpc_primary_environment_name (string) optional

The name of the environment where primary VPC is deployed

Default value: null

vpc_region_abbreviation_type (string) optional

Type of VPC abbreviation (either fixed or short) to use in names. See https://github.com/cloudposse/terraform-aws-utils for details.

Default value: "fixed"

vpc_secondary_environment_names (list(string)) optional

The names of the environments where secondary VPCs are deployed

Default value: [ ]

Context Variables

The following variables are defined in the context.tf file of this module and part of the terraform-null-label pattern.

additional_tag_map (map(string)) optional

Additional key-value pairs to add to each map in tags_as_list_of_maps. Not added to tags or id.
This is for some rare cases where resources want additional configuration of tags
and therefore take a list of maps with tag key, value, and additional configuration.

Required: No

Default value: { }

attributes (list(string)) optional

ID element. Additional attributes (e.g. workers or cluster) to add to id,
in the order they appear in the list. New attributes are appended to the
end of the list. The elements of the list are joined by the delimiter
and treated as a single ID element.

Required: No

Default value: [ ]

context (any) optional

Single object for setting entire context at once.
See description of individual variables for details.
Leave string and numeric variables as null to use default value.
Individual variable settings (non-null) override settings in context object,
except for attributes, tags, and additional_tag_map, which are merged.

Required: No

Default value:

{
  "additional_tag_map": {},
  "attributes": [],
  "delimiter": null,
  "descriptor_formats": {},
  "enabled": true,
  "environment": null,
  "id_length_limit": null,
  "label_key_case": null,
  "label_order": [],
  "label_value_case": null,
  "labels_as_tags": [
    "unset"
  ],
  "name": null,
  "namespace": null,
  "regex_replace_chars": null,
  "stage": null,
  "tags": {},
  "tenant": null
}

delimiter (string) optional

Delimiter to be used between ID elements.
Defaults to - (hyphen). Set to "" to use no delimiter at all.

Required: No

Default value: null

descriptor_formats (any) optional

Describe additional descriptors to be output in the descriptors output map.
Map of maps. Keys are names of descriptors. Values are maps of the form
\{<br/> format = string<br/> labels = list(string)<br/> \}
(Type is any so the map values can later be enhanced to provide additional options.)
format is a Terraform format string to be passed to the format() function.
labels is a list of labels, in order, to pass to format() function.
Label values will be normalized before being passed to format() so they will be
identical to how they appear in id.
Default is {} (descriptors output will be empty).

Required: No

Default value: { }

enabled (bool) optional

Set to false to prevent the module from creating any resources
Required: No

Default value: null

environment (string) optional

ID element. Usually used for region e.g. 'uw2', 'us-west-2', OR role 'prod', 'staging', 'dev', 'UAT'
Required: No

Default value: null

id_length_limit (number) optional

Limit id to this many characters (minimum 6).
Set to 0 for unlimited length.
Set to null for keep the existing setting, which defaults to 0.
Does not affect id_full.

Required: No

Default value: null

label_key_case (string) optional

Controls the letter case of the tags keys (label names) for tags generated by this module.
Does not affect keys of tags passed in via the tags input.
Possible values: lower, title, upper.
Default value: title.

Required: No

Default value: null

label_order (list(string)) optional

The order in which the labels (ID elements) appear in the id.
Defaults to ["namespace", "environment", "stage", "name", "attributes"].
You can omit any of the 6 labels ("tenant" is the 6th), but at least one must be present.

Required: No

Default value: null

label_value_case (string) optional

Controls the letter case of ID elements (labels) as included in id,
set as tag values, and output by this module individually.
Does not affect values of tags passed in via the tags input.
Possible values: lower, title, upper and none (no transformation).
Set this to title and set delimiter to "" to yield Pascal Case IDs.
Default value: lower.

Required: No

Default value: null

labels_as_tags (set(string)) optional

Set of labels (ID elements) to include as tags in the tags output.
Default is to include all labels.
Tags with empty values will not be included in the tags output.
Set to [] to suppress all generated tags.
Notes:
The value of the name tag, if included, will be the id, not the name.
Unlike other null-label inputs, the initial setting of labels_as_tags cannot be
changed in later chained modules. Attempts to change it will be silently ignored.

Required: No

Default value:

[
  "default"
]

name (string) optional

ID element. Usually the component or solution name, e.g. 'app' or 'jenkins'.
This is the only ID element not also included as a tag.
The "name" tag is set to the full id string. There is no tag with the value of the name input.

Required: No

Default value: null

namespace (string) optional

ID element. Usually an abbreviation of your organization name, e.g. 'eg' or 'cp', to help ensure generated IDs are globally unique
Required: No

Default value: null

regex_replace_chars (string) optional

Terraform regular expression (regex) string.
Characters matching the regex will be removed from the ID elements.
If not set, "/[^a-zA-Z0-9-]/" is used to remove all characters other than hyphens, letters and digits.

Required: No

Default value: null

stage (string) optional

ID element. Usually used to indicate role, e.g. 'prod', 'staging', 'source', 'build', 'test', 'deploy', 'release'
Required: No

Default value: null

tags (map(string)) optional

Additional tags (e.g. {'BusinessUnit': 'XYZ'}).
Neither the tag keys nor the tag values will be modified by this module.

Required: No

Default value: { }

tenant (string) optional

ID element (Rarely used, not included by default). A customer identifier, indicating who this instance of a resource is for
Required: No

Default value: null

Outputs

acm_ssm_parameter

The SSM parameter for the ACM cert.

certificate

The ACM certificate information.

default_dns_zone_id

Default root DNS zone ID for the cluster

default_domain_name

Default root domain name (e.g. dev.example.net) for the cluster

route53_hosted_zone_protections

List of AWS Shield Advanced Protections for Route53 Hosted Zones.

zones

Subdomain and zone config

Dependencies

Requirements

• terraform, version: >= 1.0.0
• aws, version: >= 4.9.0, < 6.0.0

Providers

• aws, version: >= 4.9.0, < 6.0.0
• aws, version: >= 4.9.0, < 6.0.0

Modules

Name	Version	Source	Description
acm	0.18.0	cloudposse/acm-request-certificate/aws	n/a
iam_roles	latest	../account-map/modules/iam-roles	n/a
private_ca	1.8.0	cloudposse/stack-config/yaml//modules/remote-state	n/a
this	0.25.0	cloudposse/label/null	n/a
utils	1.4.0	cloudposse/utils/aws	n/a
vpc	1.8.0	cloudposse/stack-config/yaml//modules/remote-state	n/a

Resources

The following resources are used by this module:

• aws_route53_record.root_ns (resource)
• aws_route53_record.soa (resource)
• aws_route53_zone.default (resource)
• aws_route53_zone.private (resource)
• aws_route53_zone_association.secondary (resource)
• aws_shield_protection.shield_protection (resource)
• aws_ssm_parameter.acm_arn (resource)

Data Sources

The following data sources are used by this module:

• aws_partition.current (data source)
• aws_route53_zone.root_zone (data source)