LoadBalancer service, Oracle Container Engine (OKE) and OCI DNS

In Kubernetes, there are a few type of services (ClusterIP, NodePort, LoadBalancer). And then, there is also Ingress and Ingress Controllers. If you still find these confusing, I recommend Sandeep Dinesh’s excellent article.

Let’s explore how you can deploy a public available service on OKE and ensure it is resolvable by DNS.

I’m assuming you already have an OKE cluster running. If not, you can follow my previous post to create one.

Create the application service

kubectl apply -f https://raw.githubusercontent.com/hyder/okesamples/master/loadbalancer/hello-clusteripsvc.yaml
deployment.apps/hello-cluster created                                                                                                                                       
service/hello-cluster-service created

Verify it’s working:

kubectl proxy — port=8080

Using your browser, access the following url: http://localhost:8080/api/v1/namespaces/default/services/hello-cluster-service:80/proxy/

Create a default backend, LoadBalancer service and IngressController

kubectl apply -f https://raw.githubusercontent.com/hyder/okesamples/master/loadbalancer/default-backend.yaml
kubectl apply -f https://raw.githubusercontent.com/hyder/okesamples/master/loadbalancer/hello-ingress.rbac.yaml
kubectl apply -f https://raw.githubusercontent.com/hyder/okesamples/master/loadbalancer/hello-ingresscontroller.yaml

Create the Ingress

Download the hello-ingress.yaml:

curl -o hello-ingress.yaml https://raw.githubusercontent.com/hyder/okesamples/master/loadbalancer/hello-ingress.yaml

Edit the hello-ingress.yaml:

spec:
  rules:
  # replace www.example.org with your FQDN
  - host: www.example.org

You can now create the Ingress:

kubectl apply -f hello-ingress.yaml

Testing the ingress

Get the public IP address of the Load Balancer and try to access it directly:

The public IP address will be under the EXTERNAL-IP column. In the above example, the public IP address of the Load Balancer is 129.146.154.77

If you try to access the hello service using the IP Address in your browser, this will return you “default backend — 404”. This is because in the Ingress we created, we specified the rule to be host-based instead of IP-based:

spec:
  rules:
  - host: www.example.org

and the host value in the HTTP request header in your browser is the IP Address for which there is no rule. Since there’s no matching rule, the request is serviced by the default backend.

Edit your local hosts file and add an entry and ensure the host matches what you entered in the ingress:

129.146.154.77 www.example.org

Now access the host using your browser and you should be able to see the Helloworld page.

Caveat: This will not work if you are testing from a network behind a proxy.

Configuring DNS in OCI

1. Login to OCI Console and navigate to Edge Services > DNS Zone Management
2. Create a Zone and ensure the zone name matches your domain name e.g. example.com.
3. Once it’s created, click on the zone and note the nameservers for your zone.
4. Login to your DNS registrar e.g. Dyn, GoDaddy and change your nameserver to point to the zones in your zone in step 3. This may take a while to be effective.
5. Go back to OCI Console and click on ‘Add Record’
6. Choose ‘A — IPv4 Address’
7. Add the FQDN e.g. www.example.org
   (N.B. you only need to add the hostname in the name field)
8. In the address field, add the public IP address of the Load Balancer.
9. Add a TTL value e.g. 3600
10. Click on ‘Submit’ and then ‘Publish Changes’
11. Remote the entry from your hosts file you added in the previous step.
12. Once the change by your DNS provider and other networks is effective, you should be able to access the Helloworld page using your FQDN in the browser.

For a quick introduction to DNS, you can check these slides.

Note — Free Tier users may experience changes to services included with their account.