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Setting up ExternalDNS for VinylDNS

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

The environment vars VINYLDNS_ACCESS_KEY, VINYLDNS_SECRET_KEY, and VINYLDNS_HOST will be needed to run ExternalDNS with VinylDNS.

Create a sample deployment and service for external-dns to use

Run an application and expose it via a Kubernetes Service:

$ kubectl run nginx --image=nginx --replicas=1 --port=80
$ kubectl expose deployment nginx --port=80 --target-port=80 --type=LoadBalancer

Annotate the Service with your desired external DNS name. Make sure to change example.org to your domain.

$ kubectl annotate service nginx "external-dns.alpha.kubernetes.io/hostname=nginx.example.org."

After the service is up and running, it should get an EXTERNAL-IP. At first this may showing as <pending>

$ kubectl get svc
NAME         CLUSTER-IP   EXTERNAL-IP   PORT(S)        AGE
kubernetes   10.0.0.1     <none>        443/TCP        1h
nginx        10.0.0.115   <pending>     80:30543/TCP   10s

Once it’s available

% kubectl get svc
NAME         CLUSTER-IP   EXTERNAL-IP   PORT(S)        AGE
kubernetes   10.0.0.1     <none>        443/TCP        1h
nginx        10.0.0.115   34.x.x.x      80:30543/TCP   2m

Deploy ExternalDNS to Kubernetes

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

Note for examples below

When using registry=txt option, make sure to also use the txt-prefix and txt-owner-id options as well. If you try to create a TXT record in VinylDNS without a prefix, it will try to create a TXT record with the same name as your actual DNS record and fail (creating a stranded record external-dns cannot manage).

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:
        - --provider=vinyldns
        - --source=service
        - --domain-filter=example.com # (optional) limit to only example.com domains; change to match the zone created above.
        - --registry=txt
        - --txt-owner-id=grizz
        - --txt-prefix=txt-
        env:
        - name: VINYLDNS_HOST
          value: "YOUR_VINYLDNS_HOST"
        - name: VINYLDNS_ACCESS_KEY
          value: "YOUR_VINYLDNS_ACCESS_KEY"
        - name: VINYLDNS_SECRET_KEY
          value: "YOUR_VINYLDNS_SECRET_KEY"

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"]
---
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:
      serviceAccountName: external-dns
      containers:
      - name: external-dns
        image: k8s.gcr.io/external-dns/external-dns:v0.7.6
        args:
        - --provider=vinyldns
        - --source=service
        - --domain-filter=example.com # (optional) limit to only example.com domains; change to match the zone created above.
        - --registry=txt
        - --txt-owner-id=grizz
        - --txt-prefix=txt-
        env:
        env:
        - name: VINYLDNS_HOST
          value: "YOUR_VINYLDNS_HOST"
        - name: VINYLDNS_ACCESS_KEY
          value: "YOUR_VINYLDNS_ACCESS_KEY"
        - name: VINYLDNS_SECRET_KEY
          value: "YOUR_VINYLDNS_SECRET_KEYY

Running a locally built version pointed to the above nginx service

Make sure your kubectl is configured correctly. Assuming you have the sources, build and run it like below.

The vinyl access details needs to exported to the environment before running.

make
# output skipped

export VINYLDNS_HOST=<fqdn of vinyl dns api>
export VINYLDNS_ACCESS_KEY=<access key>
export VINYLDNS_SECRET_KEY=<secret key>

./build/external-dns \
    --provider=vinyldns \
    --source=service \
    --domain-filter=elements.capsps.comcast.net. \
    --zone-id-filter=20e8bfd2-3a70-4e1b-8e11-c9c1948528d3 \
    --registry=txt \
    --txt-owner-id=grizz \
    --txt-prefix=txt- \
    --namespace=default \
    --once \
    --dry-run \
    --log-level debug

INFO[0000] running in dry-run mode. No changes to DNS records will be made.
INFO[0000] Created Kubernetes client https://some-k8s-cluster.example.com
INFO[0001] Zone: [nginx.example.org.]
# output skipped

Having --dry-run=true and --log-level=debug is a great way to see exactly what VinylDNS is doing or is about to do.

Last update: June 3, 2021
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