kubernetes Getting started with kubernetes Hello World

Example

Once your Kubernetes cluster is running and kubectl is configured you could run your first application with a few steps. This can be done using the imperative commands which doesn't need configuration files.

In order to run an application you need to provide a deployment name (bootcamp), the container image location (docker.io/jocatalin/kubernetes-bootcamp:v1) and the port (8080)

$ kubectl run bootcamp --image=docker.io/jocatalin/kubernetes-bootcamp:v1 --port=8080

Confirm that it worked with:

$ kubectl get deployments
NAME                  DESIRED   CURRENT   UP-TO-DATE   AVAILABLE   AGE
bootcamp               1         1         1            1         6s

To expose your application and make it accessible from the outside run:

$ kubectl expose deployment/bootcamp --type="LoadBalancer" --port 8080

Confirm that it worked with:

$ kubectl get services
NAME                  CLUSTER-IP   EXTERNAL-IP         PORT(S)    AGE
kubernetes            10.0.0.1     <none>              443/TCP    3m
bootcamp              10.3.245.61  104.155.111.170     8080:32452/TCP   2m

To access the services, use the external IP and the application port e.g. like this:

$ export EXTERNAL_IP=$(kubectl get service bootcamp --output=jsonpath='{.status.loadBalancer.ingress[0].ip}')
$ export PORT=$(kubectl get services --output=jsonpath='{.items[0].spec.ports[0].port}')
$ curl "$EXTERNAL_IP:$PORT"
Hello Kubernetes bootcamp! | Running on: bootcamp-390780338-2fhnk | v=1

The same could be done manually with the data provided in:

$ kubectl describe service bootcamp
Name:                   bootcamp
Namespace:              default
Labels:                 run=bootcamp
Selector:               run=bootcamp
Type:                   LoadBalancer
IP:                     10.3.245.61
LoadBalancer Ingress:   104.155.111.170
Port:                   <unset> 8080/TCP
NodePort:               <unset> 32452/TCP
Endpoints:              10.0.0.3:8080
... events and details left out ....

$ export NODE=104.155.111.170
$ export PORT=8080

Once this worked you can scale up your application with:

$ kubectl scale deployments/bootcamp --replicas=4

And check the result with:

$ kubectl get deployments
NAME                  DESIRED   CURRENT   UP-TO-DATE   AVAILABLE   AGE
bootcamp               4         4         4            4         30s

$ curl "$EXTERNAL_IP:$PORT"
Hello Kubernetes bootcamp! | Running on: bootcamp-390780338-2fhnk | v=1
$ curl "$EXTERNAL_IP:$PORT"
Hello Kubernetes bootcamp! | Running on: bootcamp-390780338-gmtv5 | v=1

Mind the changing pod id.

In order to push out a new application version run:

kubectl set image deployments/bootcamp bootcamp=jocatalin/kubernetes-bootcamp:v2

And confirm it with:

$ curl "$EXTERNAL_IP:$PORT"
Hello Kubernetes bootcamp! | Running on: bootcamp-284539476-gafwev3 | v=2

Cleaning up is finally done with:

$ kubectl delete deployment bootcamp
$ kubectl delete service bootcamp