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Understanding the External DNS Operator

To provide name resolution for services and routes from an External DNS provider to OKD, use the External DNS Operator. This Operator deploys and manages ExternalDNS to synchronize your cluster resources with the external provider.

External DNS Operator domain name limitations

To prevent configuration errors when deploying the ExternalDNS resource, review the domain name limitations enforced by the External DNS Operator. Understanding these constraints ensures that your requested hostnames and domains are compatible with your underlying DNS provider.

The External DNS Operator uses the TXT registry that adds the prefix for TXT records. This reduces the maximum length of the domain name for TXT records. A DNS record cannot be present without a corresponding TXT record, so the domain name of the DNS record must follow the same limit as the TXT records. For example, a DNS record of <domain_name_from_source> results in a TXT record of external-dns-<record_type>-<domain_name_from_source>.

The domain name of the DNS records generated by the External DNS Operator has the following limitations:

Record type Number of characters

CNAME

44

Wildcard CNAME records on AzureDNS

42

A

48

Wildcard A records on AzureDNS

46

The following error shows in the External DNS Operator logs if the generated domain name exceeds any of the domain name limitations:

time="2022-09-02T08:53:57Z" level=error msg="Failure in zone test.example.io. [Id: /hostedzone/Z06988883Q0H0RL6UMXXX]"
time="2022-09-02T08:53:57Z" level=error msg="InvalidChangeBatch: [FATAL problem: DomainLabelTooLong (Domain label is too long) encountered with 'external-dns-a-hello-openshift-aaaaaaaaaa-bbbbbbbbbb-ccccccc']\n\tstatus code: 400, request id: e54dfd5a-06c6-47b0-bcb9-a4f7c3a4e0c6"

Deploying the External DNS Operator

You can deploy the External DNS Operator on-demand from the Software Catalog. Deploying the External DNS Operator creates a Subscription object.

The External DNS Operator implements the External DNS API from the olm.openshift.io API group. The External DNS Operator updates services, routes, and external DNS providers.

Prerequisites

  • You have installed the yq CLI tool.

Procedure

  1. Check the name of an install plan, such as install-zcvlr, by running the following command:

    $ oc -n external-dns-operator get sub external-dns-operator -o yaml | yq '.status.installplan.name'

  2. Check if the status of an install plan is Complete by running the following command:

    $ oc -n external-dns-operator get ip <install_plan_name> -o yaml | yq '.status.phase'

  3. View the status of the external-dns-operator deployment by running the following command:

    $ oc get -n external-dns-operator deployment/external-dns-operator
    Example output
    NAME                    READY     UP-TO-DATE   AVAILABLE   AGE
external-dns-operator   1/1       1            1           23h

Viewing External DNS Operator logs

To troubleshoot DNS configuration issues, view the External DNS Operator logs. Use the oc logs command to retrieve diagnostic information directly from the Operator pod.

Procedure

  • View the logs of the External DNS Operator by running the following command:

    $ oc logs -n external-dns-operator deployment/external-dns-operator -c external-dns-operator