Setting up ExternalDNS for Services on AWS

This tutorial describes how to setup ExternalDNS for usage within a Kubernetes cluster on AWS.

Create a DNS zone which will contain the managed DNS records.

$ aws route53 create-hosted-zone --name "external-dns-test.teapot.zalan.do." --caller-reference "external-dns-test-$(date +%s)"

Make a note of the ID of the hosted zone you just created.

$ aws route53 list-hosted-zones-by-name --dns-name "external-dns-test.teapot.zalan.do." | jq -r '.HostedZones[0].Id'
/hostedzone/Z16P7IEWFWZ4RB

Make a note of the nameservers that were assigned to your new zone.

$ aws route53 list-resource-record-sets --hosted-zone-id "/hostedzone/Z16P7IEWFWZ4RB" \
    --query "ResourceRecordSets[?Type == 'NS']" | jq -r '.[0].ResourceRecords[].Value'
ns-1455.awsdns-53.org.
ns-1694.awsdns-19.co.uk.
ns-764.awsdns-31.net.
ns-62.awsdns-07.com.

In this case it's the ones shown above but your's will differ.

If you decide not to create a new zone but reuse an existing one, make sure it's currently unused and empty. This version of ExternalDNS will remove all records it doesn't recognize from the zone.

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

apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  name: external-dns
spec:
  strategy:
    type: Recreate
  template:
    metadata:
      labels:
        app: external-dns
    spec:
      containers:
      - name: external-dns
        image: registry.opensource.zalan.do/teapot/external-dns:v0.2.0
        args:
        - --in-cluster
        - --zone=Z16P7IEWFWZ4RB
        - --source=service
        - --provider=aws
        - --dry-run=false

Create the following sample application to test that ExternalDNS works.

apiVersion: v1
kind: Service
metadata:
  name: nginx
  annotations:
    external-dns.alpha.kubernetes.io/hostname: nginx.external-dns-test.teapot.zalan.do.
spec:
  type: LoadBalancer
  ports:
  - port: 80
    targetPort: 80
  selector:
    app: nginx

---

apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  name: nginx
spec:
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - image: nginx
        name: nginx
        ports:
        - containerPort: 80

After roughly two minutes check that a corresponding DNS record for your service was created.

$ aws route53 list-resource-record-sets --hosted-zone-id "/hostedzone/Z16P7IEWFWZ4RB" \
    --query "ResourceRecordSets[?Name == 'nginx.external-dns-test.teapot.zalan.do.']|[?Type == 'CNAME']"
[
    {
        "ResourceRecords": [
            {
                "Value": "ae11c2360188411e7951602725593fd1-1224345803.eu-central-1.elb.amazonaws.com"
            }
        ],
        "Type": "CNAME",
        "Name": "nginx.external-dns-test.teapot.zalan.do.",
        "TTL": 300
    }
]

Let's check that we can resolve this DNS name. We'll ask the nameservers assigned to your zone first.

$ dig +short @ns-1455.awsdns-53.org. nginx.external-dns-test.teapot.zalan.do.
ae11c2360188411e7951602725593fd1-1224345803.eu-central-1.elb.amazonaws.com.

If you hooked up your DNS zone with its parent zone correctly you can use curl to access your site.

$ curl nginx.external-dns-test.teapot.zalan.do.
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
...
</head>
<body>
...
</body>
</html>

Ingress objects on AWS require a separately deployed Ingress controller which we'll describe in another tutorial.

Clean up

Make sure to delete all Service objects before terminating the cluster so all load balancers get cleaned up correctly.

$ kubectl delete service nginx

Give ExternalDNS some time to clean up the DNS records for you. Then delete the hosted zone.

$ aws route53 delete-hosted-zone --id /hostedzone/Z16P7IEWFWZ4RB

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Setting up ExternalDNS for Services on AWS

Clean up

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