Demo Services

In this guide, we'll walk through exposing a Kubernetes application using a Service resource. After deploying your application using a Deployment resource, you can make it accessible to users through a web browser by creating a Service.

Verify Your Deployment

Before exposing your application, verify that your deployment is running correctly. In our example, we have a deployment named "myapp-deployment" that manages six replicas (six Pods) in the cluster:

kubectl get deployment
NAME               READY   UP-TO-DATE   AVAILABLE   AGE
myapp-deployment   6/6     6            6           23m

Create a Service Configuration

Now that your application is running, let’s expose it using a Kubernetes Service. Follow these steps:

1. Open your editor and navigate to the directory where you store your configuration files. For better organization, you can create a directory called service.
2. Inside the service directory, create a file named service-definition.yaml.

Define the Service API and Specifications

Begin by defining the API version and kind within your YAML file. Paste in the following configuration:

apiVersion: v1
kind: Service
metadata:
  name: myapp-service
spec:
  type: NodePort
  ports:
    - port: 80
      targetPort: 80
      nodePort: 30004

In this configuration:

• The apiVersion is set to v1 as this is the version used for services.
• The kind is specified as Service.
• The metadata section assigns the service a name: myapp-service.
• Within the spec section:
  • The service type is NodePort, which allows external access via a node port (ideal for Minikube).
  • The service listens on port 80, mapping it directly to port 80 on the Pods.
  • The nodePort is set to 30004 – an allowable value between 30000 and 32767 that exposes the service externally.

Bind the Service to Your Pods

To associate the service with the correct set of Pods, add a selector. Verify that your deployment YAML includes appropriate labels (e.g., app: myapp). Then, update your YAML file with the selector field:

apiVersion: v1
kind: Service
metadata:
  name: myapp-service
spec:
  type: NodePort
  ports:
    - port: 80
      targetPort: 80
      nodePort: 30004
  selector:
    app: myapp

Deploy the Service

Once your service definition is complete, save the file and navigate to its directory to confirm its existence:

admin@ubuntu-server service # ls
service-definition.yaml
admin@ubuntu-server service # cat service-definition.yaml

Next, create the service in your Kubernetes cluster by executing:

kubectl create -f service-definition.yaml
service/myapp-service created
kubectl get svc

The output will list your services, including the new NodePort service with its corresponding ClusterIP and port mappings:

NAME             TYPE        CLUSTER-IP       EXTERNAL-IP   PORT(S)         AGE
kubernetes       ClusterIP   10.96.0.1        <none>        443/TCP         24h
myapp-service    NodePort    10.101.76.121    <none>        80:30004/TCP    5s

Access Your Application

Since we're using Minikube, retrieve the service URL with:

minikube service myapp-service --url

This command will output a URL resembling:

http://192.168.99.101:30004

Copy the URL and paste it into your web browser. You should see the default Nginx web page, confirming that the Nginx application is accessible and running as expected.

Happy deploying, and see you in the next tutorial!