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Setting up ExternalDNS for Services on Plural

This tutorial describes how to setup ExternalDNS for usage within a Kubernetes cluster using Plural DNS.

Make sure to use >=0.12.3 version of ExternalDNS for this tutorial.

Creating Plural Credentials

A secret containing the a Plural access token is needed for this provider. You can get a token for your user here.

To create the secret you can run kubectl create secret generic plural-env --from-literal=PLURAL_ACCESS_TOKEN=<replace-with-your-access-token>.

Deploy ExternalDNS

Connect your kubectl client to the cluster you want to test ExternalDNS with.
Then apply one of the following manifests file to deploy ExternalDNS.

Manifest (for clusters without RBAC enabled)

apiVersion: apps/v1
kind: Deployment
metadata:
  name: external-dns
spec:
  strategy:
    type: Recreate
  selector:
    matchLabels:
      app: external-dns
  template:
    metadata:
      labels:
        app: external-dns
    spec:
      containers:
      - name: external-dns
        image: k8s.gcr.io/external-dns/external-dns:v0.7.6
        args:
        - --source=service # ingress is also possible
        - --domain-filter=example.com # (optional) limit to only example.com domains; change to match the zone created above.
        - --provider=plural
        - --plural-cluster=example-plural-cluster
        - --plural-provider=aws # gcp, azure, equinix and kind are also possible
        env:
        - name: PLURAL_ACCESS_TOKEN
          valueFrom:
            secretKeyRef:
              key: PLURAL_ACCESS_TOKEN
              name: plural-env
        - name: PLURAL_ENDPOINT # (optional) use an alternative endpoint for Plural; defaults to https://app.plural.sh
          value: https://app.plural.sh

Manifest (for clusters with RBAC enabled)

apiVersion: v1
kind: ServiceAccount
metadata:
  name: external-dns
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  name: external-dns
rules:
- apiGroups: [""]
  resources: ["services","endpoints","pods"]
  verbs: ["get","watch","list"]
- apiGroups: ["extensions","networking.k8s.io"]
  resources: ["ingresses"] 
  verbs: ["get","watch","list"]
- apiGroups: [""]
  resources: ["nodes"]
  verbs: ["list", "watch"]
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  name: external-dns-viewer
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: external-dns
subjects:
- kind: ServiceAccount
  name: external-dns
  namespace: default
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: external-dns
spec:
  strategy:
    type: Recreate
  selector:
    matchLabels:
      app: external-dns
  template:
    metadata:
      labels:
        app: external-dns
    spec:
      containers:
      - name: external-dns
        image: k8s.gcr.io/external-dns/external-dns:v0.7.6
        args:
        - --source=service # ingress is also possible
        - --domain-filter=example.com # (optional) limit to only example.com domains; change to match the zone created above.
        - --provider=plural
        - --plural-cluster=example-plural-cluster
        - --plural-provider=aws # gcp, azure, equinix and kind are also possible
        env:
        - name: PLURAL_ACCESS_TOKEN
          valueFrom:
            secretKeyRef:
              key: PLURAL_ACCESS_TOKEN
              name: plural-env
        - name: PLURAL_ENDPOINT # (optional) use an alternative endpoint for Plural; defaults to https://app.plural.sh
          value: https://app.plural.sh

Deploying an Nginx Service

Create a service file called ‘nginx.yaml’ with the following contents:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx
spec:
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - image: nginx
        name: nginx
        ports:
        - containerPort: 80
---
apiVersion: v1
kind: Service
metadata:
  name: nginx
  annotations:
    external-dns.alpha.kubernetes.io/hostname: example.com
spec:
  selector:
    app: nginx
  type: LoadBalancer
  ports:
    - protocol: TCP
      port: 80
      targetPort: 80

Note the annotation on the service; use the same hostname as the Plural DNS zone created above. The annotation may also be a subdomain
of the DNS zone (e.g. ‘www.example.com’).

By setting the TTL annotation on the service, you have to pass a valid TTL, which must be 120 or above.
This annotation is optional, if you won’t set it, it will be 1 (automatic) which is 300.

ExternalDNS uses this annotation to determine what services should be registered with DNS. Removing the annotation
will cause ExternalDNS to remove the corresponding DNS records.

Create the deployment and service:

$ kubectl create -f nginx.yaml

Depending where you run your service it can take a little while for your cloud provider to create an external IP for the service.

Once the service has an external IP assigned, ExternalDNS will notice the new service IP address and synchronize
the Plural DNS records.

Verifying Plural DNS records

Check your Plural domain overview to view the domains associated with your Plural account. There you can view the records for each domain.

The records should show the external IP address of the service as the A record for your domain.

Cleanup

Now that we have verified that ExternalDNS will automatically manage Plural DNS records, we can delete the tutorial’s example:

```
$ kubectl delete -f nginx.yaml
$ kubectl delete -f externaldns.yaml

Last update: July 29, 2022
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