Configuring ExternalDNS to use the OpenShift Route Source

This tutorial describes how to configure ExternalDNS to use the OpenShift Route source. It is meant to supplement the other provider-specific setup tutorials.

Prepare ROUTER_CANONICAL_HOSTNAME in default/router deployment

Read and go through Finding the Host Name of the Router. If no ROUTER_CANONICAL_HOSTNAME is set, you must annotate each route with external-dns.alpha.kubernetes.io/target!

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=openshift-route
        - --domain-filter=external-dns-test.my-org.com # will make ExternalDNS see only the hosted zones matching provided domain, omit to process all available hosted zones
        - --provider=aws
        - --policy=upsert-only # would prevent ExternalDNS from deleting any records, omit to enable full synchronization
        - --aws-zone-type=public # only look at public hosted zones (valid values are public, private or no value for both)
        - --registry=txt
        - --txt-owner-id=my-identifier

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"]
- apiGroups: ["route.openshift.io"]
  resources: ["routes"]
  verbs: ["get","watch","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:
        - --source=openshift-route
        - --domain-filter=external-dns-test.my-org.com # will make ExternalDNS see only the hosted zones matching provided domain, omit to process all available hosted zones
        - --provider=aws
        - --policy=upsert-only # would prevent ExternalDNS from deleting any records, omit to enable full synchronization
        - --aws-zone-type=public # only look at public hosted zones (valid values are public, private or no value for both)
        - --registry=txt
        - --txt-owner-id=my-identifier

Verify External DNS works (OpenShift Route example)

The following instructions are based on the Hello Openshift.

Install a sample service and expose it

$ oc apply -f - <<EOF
apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app: hello-openshift
  name: hello-openshift
spec:
  replicas: 1
  selector:
    matchLabels:
      app: hello-openshift
  template:
    metadata:
      labels:
        app: hello-openshift
    spec:
      containers:
      - image: openshift/hello-openshift
        name: hello-openshift
---
apiVersion: v1
kind: Service
metadata:
  labels:
    app: hello-openshift
  name: hello-openshift
spec:
  ports:
  - port: 8080
    protocol: TCP
    targetPort: 8080
  selector:
    app: hello-openshift
  sessionAffinity: None
  type: ClusterIP
---
apiVersion: route.openshift.io/v1
kind: Route
metadata:
  name: hello-openshift
spec:
  host: hello-openshift.example.com
  to:
    kind: Service
    name: hello-openshift
    weight: 100
  wildcardPolicy: None
EOF

Access the sample route using `curl`

$ curl -i http://hello-openshift.example.com
HTTP/1.1 200 OK
Date: Fri, 10 Apr 2020 09:36:41 GMT
Content-Length: 17
Content-Type: text/plain; charset=utf-8

Hello OpenShift!

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