Exposing kubernetes service outside the cluster for development purposes

Question

Is it somehow possible to expose a kubernetes service to the outside world? I am currently developping an application which need to communicate with a service, and to do so I need to know the pod ip and port address, which I withing the kubernetes cluster can get with the kubernetes services linked to it, but outside the cluster I seem to be unable to find it, or expose it?

apiVersion: v1
kind: Service
metadata:
  name: kafka-broker
spec:
  ports:
  - name: broker
    port: 9092
    protocol: TCP
    targetPort: kafka
  selector:
    app: kafka
  sessionAffinity: None
  type: ClusterIP

I could containerize the application, put it in a pod, and run it within kubernetes, but for fast development it seems tedious to have to go through this, for testing such a small things such as connectivity?

Someway i can expose the service, and thereby reach the application in its selector?

you can use node port to expose the port on host machine. refer this https://stackoverflow.com/questions/49981601/difference-between-targetport-and-port-in-kubernetes-service-definition/55183861#55183861. — Manikanta P, Jan 08 '20 at 06:47

score 2 · Answer 1 · answered Jan 08 '20 at 14:15

In order to expose your Kubernetes service to the internet you must change the ServiceType.

Your service is using the default which is ClusterIP, it exposes the Service on a cluster-internal IP, making it only reachable within the cluster.

1 - If you use cloud provider like AWS or GCP The best option for you is to use the LoadBalancer Service Type: which automatically exposes to the internet using the provider Load Balancer.

Run: kubectl expose deployment deployment-name --type=LoadBalancer --name=service-name

Where deployment-name must be replaced by your actual deploy name. and the same goes for the desired service-name

wait a few minutes and the kubectl get svc command will give you the external IP and PORT:

owilliam@minikube:~$ kubectl get svc
NAME               TYPE           CLUSTER-IP      EXTERNAL-IP   PORT(S)      AGE
kubernetes         ClusterIP      10.96.0.1       <none>        443/TCP      4d21h
nginx-service-lb   LoadBalancer   10.96.125.208   0.0.0.0     80:30081/TCP   36m

2 - If you are running Kubernetes locally (like Minikube) the best option is the Nodeport Service Type: It it exposes the service to the Cluster Node( the hosting computer). Which is safer for testing purposes than exposing the service to the whole internet.

Run: kubectl expose deployment deployment-name --type=NodePort --name=service-name

Where deployment-name must be replaced by your actual deploy name. and the same goes for the desired service-name

Bellow are my outputs after exposing an Nginx webserver to the NodePort for your reference:

user@minikube:~$ kubectl get svc
NAME           TYPE        CLUSTER-IP    EXTERNAL-IP   PORT(S)        AGE
kubernetes     ClusterIP   10.96.0.1     <none>        443/TCP        4d21h
service-name   NodePort    10.96.33.84   <none>        80:31198/TCP   4s

user@minikube:~$ minikube service list
|----------------------|---------------------------|-----------------------------|-----|
|      NAMESPACE       |           NAME            |         TARGET PORT         | URL |
|----------------------|---------------------------|-----------------------------|-----|
| default              | kubernetes                | No node port                |
| default              | service-name              | http://192.168.39.181:31198 |
| kube-system          | kube-dns                  | No node port                |
| kubernetes-dashboard | dashboard-metrics-scraper | No node port                |
| kubernetes-dashboard | kubernetes-dashboard      | No node port                |
|----------------------|---------------------------|-----------------------------|-----|
user@minikube:~$ curl http://192.168.39.181:31198 
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
...//// suppressed output
<p><em>Thank you for using nginx.</em></p>
</body>
</html>
user@minikube:~$

score 1 · Answer 2 · answered Jan 08 '20 at 09:52

you can use: NodePort or Load balancer type services as mentioned in other answers. or even ingress.

But as you are asking for developer purpose only, I suggest to start a testing pod in given namespace and check connectivity from that pod. You can get actual SSH access to running pod kubectl exec -it {PODNAME} /bin/sh

you can also try tools like - kubefwd - squash - stern

score 0 · Answer 3 · answered Jan 08 '20 at 07:11

0

Use Service type as NodePort or Loadbalancer. Latter is recommended if you are running in cloud like Azure,AWS or GCD

refer the same below

apiVersion: v1
kind: Service
metadata:
  name: kafka-broker
spec:
  ports:
  - name: broker
    port: 9092
    protocol: TCP
    targetPort: kafka
  selector:
    app: kafka
  sessionAffinity: None
  type: NodePort

answered Jan 08 '20 at 07:11

P Ekambaram

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how is it accessible`? – some Jan 08 '20 at 07:26
use HOSTNAME:NODEPORT – P Ekambaram Jan 08 '20 at 16:03

Exposing kubernetes service outside the cluster for development purposes

3 Answers3