The ExternalDNS Operator allows you to deploy and manage ExternalDNS, a cluster-internal component which makes Kubernetes resources discoverable through public DNS servers. For more information about the initial motivation, see ExternalDNS Operator OpenShift Enhancement Proposal.
ExternalDNS OperatorThe following procedure describes how to deploy the ExternalDNS Operator for AWS.
Prepare your environment for the installation commands.
podman or docker):
export CONTAINER_ENGINE=podmanexport REGISTRY=quay.io
export REPOSITORY=myuser
export VERSION=1.0.0${CONTAINER_ENGINE} login ${REGISTRY} -u ${REPOSITORY}ExternalDNS Operator by building and pushing the Operator image to a registryBuild and push the Operator image to a registry:
export IMG=${REGISTRY}/${REPOSITORY}/external-dns-operator:${VERSION}
make image-build image-pushOptional: you may need to link the registry secret to external-dns-operator service account if the image is not public (Doc link):
a. Create a secret with authentication details of your image registry:
oc -n external-dns-operator create secret generic extdns-pull-secret --type=kubernetes.io/dockercfg --from-file=.dockercfg=${XDG_RUNTIME_DIR}/containers/auth.jsonb. Link the secret to external-dns-operator service account:
oc -n external-dns-operator secrets link external-dns-operator extdns-pull-secret --for=pullRun the following command to deploy the ExternalDNS Operator:
make deployThe previous step deploys the validation webhook, which requires TLS authentication for the webhook server. The
manifests deployed through the make deploy command do not contain a valid certificate and key. You must provision a valid certificate and key through other tools.
You can use a convenience script, hack/generate-certs.sh to generate the certificate bundle and patch the validation webhook config.
Important: Do not use the hack/generate-certs.sh script in a production environment.
Run the hack/generate-certs.sh script with the following inputs:
hack/generate-certs.sh --service webhook-service --webhook validating-webhook-configuration \
--secret webhook-server-cert --namespace external-dns-operatorNote: you may need to wait for the retry of the volume mount in the operator's POD
Now you can deploy an instance of ExternalDNS:
Run the following command to create the credentials secret for AWS:
kubectl -n external-dns-operator create secret generic aws-access-key \
--from-literal=aws_access_key_id=${ACCESS_KEY_ID} \
--from-literal=aws_secret_access_key=${ACCESS_SECRET_KEY}Note: See this guide for instructions specific to other providers.
Run the following command:
# for AWS
kubectl apply -k config/samples/awsNote: For other providers, see config/samples/.
ExternalDNS Operator using a custom catalog image on OperatorHubBuild and push the operator image to the registry:
export IMG=${REGISTRY}/${REPOSITORY}/external-dns-operator:${VERSION}
make image-build image-pushBuild and push the bundle image to the registry:
export BUNDLE_IMG=${REGISTRY}/${REPOSITORY}/external-dns-operator-bundle:${VERSION}
make bundle-image-build bundle-image-pushBuild and push the catalog image to the registry:
export CATALOG_IMG=${REGISTRY}/${REPOSITORY}/external-dns-operator-catalog:${VERSION}
make catalog-image-build catalog-image-pushOptional: you may need to link the registry secret to the pod of external-dns-operator created in the openshift-marketplace namespace if the image is not made public (Doc link). If you are using podman then these are the instructions:
a. Create a secret with authentication details of your image registry:
oc -n openshift-marketplace create secret generic extdns-olm-secret --type=kubernetes.io/dockercfg --from-file=.dockercfg=${XDG_RUNTIME_DIR}/containers/auth.jsonb. Link the secret to default service account:
oc -n openshift-marketplace secrets link default extdns-olm-secret --for=pullCreate the CatalogSource object:
cat <<EOF | oc apply -f -
apiVersion: operators.coreos.com/v1alpha1
kind: CatalogSource
metadata:
name: external-dns-operator
namespace: openshift-marketplace
spec:
sourceType: grpc
image: ${CATALOG_IMG}
EOFCreate the operator namespace:
oc create namespace external-dns-operator
oc label namespace external-dns-operator openshift.io/cluster-monitoring=trueCreate the OperatorGroup object to scope the operator to external-dns-operator namespace:
cat <<EOF | oc apply -f -
apiVersion: operators.coreos.com/v1
kind: OperatorGroup
metadata:
name: external-dns-operator
namespace: external-dns-operator
spec:
targetNamespaces:
- external-dns-operator
EOFCreate the Subscription object:
cat <<EOF | oc apply -f -
apiVersion: operators.coreos.com/v1alpha1
kind: Subscription
metadata:
name: external-dns-operator
namespace: external-dns-operator
spec:
channel: stable-v1
name: external-dns-operator
source: external-dns-operator
sourceNamespace: openshift-marketplace
EOFNote: The steps starting from the 7th can be replaced with the following actions in the web console: Navigate to Operators -> OperatorHub, search for the ExternalDNS Operator, and install it in the external-dns-operator namespace.
Now you can deploy an instance of ExternalDNS:
# for AWS
oc apply -k config/samples/awsNote: For other providers, see config/samples/.
Optional: you may need to link the registry secret to the operand's service account if your custom image is not public (Doc link):
a. Create a secret with authentication details of your image registry:
oc -n external-dns-operator create secret generic extdns-pull-secret --type=kubernetes.io/dockercfg --from-file=.dockercfg=${XDG_RUNTIME_DIR}/containers/auth.jsonb. Find the service account of your operand:
oc -n external-dns-operator get sa | grep external-dnsc. Link the secret to found service account:
oc -n external-dns-operator secrets link external-dns-sample-aws extdns-pull-secret --for=pullPatch RELATED_IMAGE_EXTERNAL_DNS environment variable's value with your custom operand image:
# "external-dns-operator" container has index 0
# "RELATED_IMAGE_EXTERNAL_DNS" environment variable has index 1
oc -n external-dns-operator patch deployment external-dns-operator --type='json' -p='[{"op": "replace", "path": "/spec/template/spec/containers/0/env/1/value", "value":"<CUSTOM_IMAGE_TAG>"}]'oc -n external-dns-operator patch subscription external-dns-operator --type='json' -p='[{"op": "add", "path": "/spec/config", "value":{"env":[{"name":"RELATED_IMAGE_EXTERNAL_DNS","value":"<CUSTOM_IMAGE_TAG>"}]}}]'Deploy the operator as described above
Set the necessary environment variables
For AWS:
export KUBECONFIG=/path/to/mycluster/kubeconfig
export DNS_PROVIDER=AWS
export AWS_ACCESS_KEY_ID=my-aws-access-key
export AWS_SECRET_ACCESS_KEY=my-aws-access-secretFor Infoblox:
export KUBECONFIG=/path/to/mycluster/kubeconfig
export DNS_PROVIDER=INFOBLOX
export INFOBLOX_GRID_HOST=myinfoblox.myorg.com
export INFOBLOX_WAPI_USERNAME=my-infoblox-username
export INFOBLOX_WAPI_PASSWORD=my-infoblox-passwordFor the other providers: check out e2e directory.
Run the test suite
make test-e2eConfiguring proxy support for ExternalDNS Operator
The ExternalDNS Operator exposes controller-runtime metrics using custom resources expected by Prometheus Operator.
ServiceMonitor object is created in the operator's namespace (by default external-dns-operator), make sure that your instance of the Prometheus Operator is properly configured to find it.
You can check .spec.serviceMonitorNamespaceSelector and .spec.serviceMonitorSelector fields of prometheus resource and edit the operator's namespace or service monitor accordingly:
kubectl -n monitoring get prometheus k8s --template='{{.spec.serviceMonitorNamespaceSelector}}{{"\n"}}{{.spec.serviceMonitorSelector}}{{"\n"}}'
map[matchLabels:map[openshift.io/cluster-monitoring:true]]
map[]For OpenShift:
oc -n openshift-monitoring get prometheus k8s --template='{{.spec.serviceMonitorNamespaceSelector}}{{"\n"}}{{.spec.serviceMonitorSelector}}{{"\n"}}'
map[matchLabels:map[openshift.io/cluster-monitoring:true]]
map[]We define the following stability levels for DNS providers:
| Provider | Status |
|---|---|
| AWS Route53 | GA |
| AWS Route53 on GovCloud | TechPreview |
| AzureDNS | GA |
| GCP Cloud DNS | GA |
| Infoblox | GA |
| BlueCat | TechPreview |
ExternalDNS Operator uses the TXT registry which implies the usage of the new format and the prefix for the TXT records.
This reduces the maximum length of the domain name for the TXT records.
Since the TXT record accompanies every DNS record, there cannot be a DNS record without a corresponding TXT record, therefore the DNS record's domain name gets hit by the same limit:
DNS record: <domain-name-from-source>
TXT record: external-dns-<record-type>-<domain-name-from-source>Please be aware that instead of the standardized 63 characters long maximum length, the domain names generated from the ExternalDNS sources have the following limits:
Example
ExternalDNS CR which uses Service of type ExternalName (to force CNAME record type) as the source for the DNS records:
$ oc get externaldns aws -o yaml
apiVersion: externaldns.olm.openshift.io/v1beta1
kind: ExternalDNS
metadata:
name: aws
spec:
provider:
type: AWS
zones:
- Z06988883Q0H0RL6UMXXX
source:
type: Service
service:
serviceType:
- ExternalName
fqdnTemplate:
- "{{.Name}}.test.example.io"The service of the following name will not pose any problems because its name is 44 characters long:
$ oc get svc
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
hello-openshift-aaaaaaaaaa-bbbbbbbbbb-cccccc ExternalName <none> somednsname.example.io 8080/TCP,8888/TCP
$ aws route53 list-resource-record-sets --hosted-zone-id=Z06988883Q0H0RL6UMXXX
RESOURCERECORDSETS external-dns-cname-hello-openshift-aaaaaaaaaa-bbbbbbbbbb-cccccc.test.example.io. 300 TXT
RESOURCERECORDS "heritage=external-dns,external-dns/owner=external-dns-aws,external-dns/resource=service/test-long-dnsname/hello-openshift-aaaaaaaaaa-bbbbbbbbbb-cccccc"
RESOURCERECORDSETS external-dns-hello-openshift-aaaaaaaaaa-bbbbbbbbbb-cccccc.test.example.io. 300 TXT
RESOURCERECORDS "heritage=external-dns,external-dns/owner=external-dns-aws,external-dns/resource=service/test-long-dnsname/hello-openshift-aaaaaaaaaa-bbbbbbbbbb-cccccc"
RESOURCERECORDSETS hello-openshift-aaaaaaaaaa-bbbbbbbbbb-cccccc.test.example.io. 300 CNAME
RESOURCERECORDS somednsname.example.ioThe service of a longer name will result in no changes on the DNS provider and the errors similar to the below ones in the ExternalDNS instance:
$ oc -n external-dns-operator logs external-dns-aws-7ddbd9c7f8-2jqjh
...
time="2022-09-02T08:53:57Z" level=info msg="Desired change: CREATE external-dns-cname-hello-openshift-aaaaaaaaaa-bbbbbbbbbb-ccccccc.test.example.io TXT [Id: /hostedzone/Z06988883Q0H0RL6UMXXX]"
time="2022-09-02T08:53:57Z" level=info msg="Desired change: CREATE external-dns-hello-openshift-aaaaaaaaaa-bbbbbbbbbb-ccccccc.test.example.io TXT [Id: /hostedzone/Z06988883Q0H0RL6UMXXX]"
time="2022-09-02T08:53:57Z" level=info msg="Desired change: CREATE hello-openshift-aaaaaaaaaa-bbbbbbbbbb-ccccccc.test.example.io A [Id: /hostedzone/Z06988883Q0H0RL6UMXXX]"
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"
...