coredns/plugin/clouddns/README.md

clouddns

Name

clouddns - enables serving zone data from GCP Cloud DNS.

Description

The clouddns plugin is useful for serving zones from resource record sets in GCP Cloud DNS. This plugin supports all Google Cloud DNS records. This plugin can be used when CoreDNS is deployed on GCP or elsewhere. Note that this plugin accesses the resource records through the Google Cloud API. For records in a privately hosted zone, it is not necessary to place CoreDNS and this plugin in the associated VPC network. In fact the private hosted zone could be created without any associated VPC and this plugin could still access the resource records under the hosted zone.

Syntax

clouddns [ZONE:PROJECT_ID:HOSTED_ZONE_NAME...] {
    credentials [FILENAME]
    endpoint ENDPOINT
    fallthrough [ZONES...]
    refresh DURATION
}

• ZONE the name of the domain to be accessed. When there are multiple zones with overlapping domains (private vs. public hosted zone), CoreDNS does the lookup in the given order here. Therefore, for a non-existing resource record, SOA response will be from the rightmost zone.

• PROJECT_ID the project ID of the Google Cloud project.

• HOSTED_ZONE_NAME the name of the hosted zone that contains the resource record sets to be accessed.

• credentials is used for reading the credential file from FILENAME (normally a .json file). This field is optional. If this field is not provided then authentication will be done automatically, e.g., through environmental variable GOOGLE_APPLICATION_CREDENTIALS. Note that CoreDNS validates that the given file has a valid credentials type, but does not validate the credentials file for malicious input. Please see Google Cloud's authentication method and validating credential configurations from external sources for more details.

• endpoint can be used to control the endpoint to use when querying Cloud DNS (optional). ENDPOINT is the URL of the endpoint to use. If this is not provided the default Cloud DNS endpoint is used. Useful for pointing at a local emulator or test environment.

• fallthrough If zone matches and no record can be generated, pass request to the next plugin. If [ZONES...] is omitted, then fallthrough happens for all zones for which the plugin is authoritative. If specific zones are listed (for example in-addr.arpa and ip6.arpa), then only queries for those zones will be subject to fallthrough.

• refresh can be used to control how long between record retrievals from Cloud DNS. It requires a duration string as a parameter to specify the duration between update cycles. Each update cycle may result in many Cloud DNS API calls depending on how many domains use this plugin and how many records are in each. Adjusting the update frequency may help reduce the potential of API throttling by Google Cloud. If not provided the default refresh is 1 minute.

Examples

Enable clouddns with implicit GCP credentials and resolve CNAMEs via 10.0.0.1:

example.org {
    clouddns example.org.:gcp-example-project:example-zone
    forward . 10.0.0.1
}

Enable clouddns with fallthrough:

example.org {
    clouddns example.org.:gcp-example-project:example-zone example.com.:gcp-example-project:example-zone-2 {
        fallthrough example.gov.
    }
}

Enable clouddns with multiple hosted zones with the same domain:

. {
    clouddns example.org.:gcp-example-project:example-zone example.com.:gcp-example-project:other-example-zone
}

Enable clouddns and refresh records every 3 minutes:

example.org {
    clouddns example.org.:gcp-example-project:example-zone {
        refresh 3m
    }
}

Enable clouddns against a custom Cloud DNS endpoint:

example.org {
    clouddns example.org.:gcp-example-project:example-zone {
        endpoint https://dns.googleapis.com
    }
}