Scale and Update Deployments

In this lab, you’ll learn how to update the number of instances a deployment has and how to modify the API backend.

For this lab, you need a running deployment of the k8sdemo application from the previous lab. If you deleted it, recreate it.

🚀 TASK: Scale apps with replicas

A replica is a copy of a pod that contains a running service. By having multiple replicas of a pod, you can ensure your deployment has the available resources to handle increasing load on your application.

kubectl provides a scale subcommand to change the size of an existing deployment. Let’s increase our capacity from a single running instance of k8sdemo up to 10 instances:

kubectl scale --replicas=4 deployment k8sdemo-backend -n default

 > deployment "k8sdemo" scaled

Kubernetes will now try to make reality match the desired state of 4 replicas by starting 2 new pods with the same configuration as the first.

To verify that your changes have been rolled out, you can run:

kubectl get pods -n default

> NAME                              READY     STATUS    RESTARTS   AGE
> k8sdemo-7d46f69d68-xcgcw          1/1       Running   0          19m
> k8sdemo-backend-9c777544b-cp59q   1/1       Running   0          12m
> k8sdemo-backend-9c777544b-jqjz9   1/1       Running   0          12m
> k8sdemo-backend-9c777544b-lwssx   1/1       Running   0          12m
> k8sdemo-backend-9c777544b-t5mlq   1/1       Running   0          12m

You should see output listing 4 replicas of your deployment.

Forward the local port again to the frontend service in your Cluster:

kubectl port-forward --namespace default $(kubectl get po -n default -l app=k8sdemo | grep k8sdemo | \awk '{print $1;}') 3000:3000

And then navigating to http://localhost:3000/ in your browser.

If you reload the webpage several times, you should see, tht the IP Address of the backend API Pod is changing between the four Pods that have been spun up.
Hit CTRL-C several times to cancel the port forward

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Kubernetes Basics: Deploy your first application

Kubernetes Basics: Stateful Deployments