First Kubernetes Deployment

In this lab, we’ll create a simple deployment with several replicas and a basic web server. After that, we’ll deploy a series of deployments to configure a fully functional monitoring service for Kubernetes.

Cleanup all previous deployments

To ensure we have enough resources, let’s delete our previous deployments.

kubectl delete all --all

Confirm all objects were deleted: You should only see the kubernetes service

kubectl get all

Create a Deployment manifest(Pod, Service, Replicas)

Using VS Code, create a lab directory $HOME/labs/lab4. In the directory, create a file called hello-world.yaml with the following content:

NOTE: the “selector” app field is the same as the deployment metadata app field.

NOTE: that the Kind is Service and Deployment. Also, note the statically declared NodePort.

apiVersion: v1
kind: Service
metadata:
  labels:
    name: hello-world-deployment
  name: hello-world-deployment
spec:
  selector:
    app: hello-world
  type: NodePort
  ports:
  - name: hello-world-deployment
    protocol: TCP
    port: 80
    nodePort: 30901
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: hello-world-deployment
spec:
  replicas: 3
  selector:
    matchLabels:
      app: hello-world
  template:
    metadata:
      labels:
        app: hello-world
    spec:
      containers:
      - name: hello-world
        image: lindison/hello-world:k8s
        ports:
        - containerPort: 80

Deploy a basic deployment

kubectl apply -f $HOME/labs/hello-world.yaml

Example output:

service/hello-world-deployment created
deployment.apps/hello-world-deployment created

List deployments

kubectl get deployment

Example output:

NAME                     READY   UP-TO-DATE   AVAILABLE   AGE
hello-world-deployment   3/3     3            3           37s

Show all Kubernetes objects:

kubectl get all 

You can see the deployment and service were successfully created.

Get the NodePort of the service

kubectl get svc hello-world-deployment

Example output:

NAME                     TYPE        CLUSTER-IP     EXTERNAL-IP   PORT(S)        AGE
hello-world-deployment   NodePort    10.98.17.127   <none>        80:30901/TCP   6s

Notice the NodePort is 30901. If you look back at the service manifest you will notice we defined a static NodePort.

Load application

Using a browser, open the web page at: http://<LEADER_IP>:30901

Replace <LEADER_IP> with your leader node’s IP address.

You will see a page similar to below:

Scaling the pods

Now that we have our application running, let’s increase the replica count to scale the deployment. First get a list of running pods.

kubectl get pods 

Example output:

NAME                                      READY   STATUS    RESTARTS   AGE
hello-world-deployment-8488f8789f-5xbql   1/1     Running   0          5m13s
hello-world-deployment-8488f8789f-969tm   1/1     Running   0          5m13s
hello-world-deployment-8488f8789f-rfp5v   1/1     Running   0          5m13s

Scale the deployment:

kubectl scale deployment hello-world-deployment --replicas=5

Confirm the deployment now has 5 replicas

kubectl get pods 

Example output:

NAME                                      READY   STATUS    RESTARTS   AGE
hello-world-deployment-8488f8789f-5q4wc   1/1     Running   0          50s
hello-world-deployment-8488f8789f-5xbql   1/1     Running   0          6m55s
hello-world-deployment-8488f8789f-768hp   1/1     Running   0          50s
hello-world-deployment-8488f8789f-969tm   1/1     Running   0          6m55s
hello-world-deployment-8488f8789f-rfp5v   1/1     Running   0          6m55s

Now run the appropriate command to scale the deployment back to 3 replicas.

Confirm the replica count is now 3

kubectl get pods 

NAME                                      READY   STATUS    RESTARTS   AGE
hello-world-deployment-8488f8789f-5xbql   1/1     Running   0          9m25s
hello-world-deployment-8488f8789f-969tm   1/1     Running   0          9m25s
hello-world-deployment-8488f8789f-rfp5v   1/1     Running   0          9m25s

Cleanup

Now remove the deployment and service

kubectl delete -f $HOME/labs/hello-world.yaml