Scaling and Managing Pods with Deployments

Introduction

In this lab, you will learn how to scale and manage Pods with Deployments in Kubernetes. Deployments are a higher-level abstraction that allow you to declaratively manage and scale replica sets of Pods. By using Deployments, you can easily update your application to a new version, roll back to a previous version, and scale your application up or down to meet changing demand.

Start the Minikube Cluster

Before creating resources, you need a running Kubernetes cluster. Minikube is a lightweight Kubernetes environment that runs on your local machine.

1. Navigate to your working directory:

   Open the terminal and navigate to the default project folder:

   cd /home/labex/project
   

2. Start Minikube:

   Start Minikube to initialize a Kubernetes cluster:

   minikube start
   

   • This command sets up a single-node Kubernetes cluster on your local machine.
   • Minikube may take a few minutes to start depending on your system's performance.

3. Verify Minikube is running:

   Check the status of the Minikube cluster:

   minikube status
   

   • Look for components like kubelet and apiserver listed as Running.
   • If the cluster is not running, rerun minikube start.

If you encounter issues starting Minikube. Use minikube delete to reset the environment if needed.

Create a Deployment

1. Create a file called my-deployment.yaml in /home/labex/project/ with the following content::

apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-deployment
spec:
  replicas: 3
  selector:
    matchLabels:
      app: my-app
  template:
    metadata:
      labels:
        app: my-app
    spec:
      containers:
        - name: my-app
          image: nginx:latest
          ports:
            - containerPort: 80

This YAML file defines a Deployment with 3 replicas, running an Nginx container. The selector field selects the Pods controlled by the Deployment based on the app label.

2. Deploy the my-deployment Deployment:

kubectl apply -f my-deployment.yaml

This will create the my-deployment Deployment and its associated ReplicaSets and Pods.

3. Verify that the Deployment has been created:

kubectl get deployments

This will show you the Deployments in your cluster, including the my-deployment Deployment.

Scale the Deployment

1. Scale up the my-deployment Deployment to 5 replicas:

kubectl scale deployment my-deployment --replicas=5

This will increase the number of replicas in the my-deployment Deployment to 5.

2. Verify that the Deployment has been scaled:

kubectl get deployments

This will show you the Deployments in your cluster, including the my-deployment Deployment with 5 replicas.

Update the Deployment

1. Edit the my-deployment Deployment to use the nginx:1.19 image:

kubectl edit deployment my-deployment

This will open the Deployment in your default text editor. Change the image field to nginx:1.19 and save the file.

2. Verify that the Deployment has been updated:

kubectl rollout status deployment/my-deployment

This will show you the status of the latest rollout of the my-deployment Deployment.

Roll Back the Deployment

1. Roll back the my-deployment Deployment to the previous version:

kubectl rollout undo deployment/my-deployment

This will roll back the my-deployment Deployment to the previous version.

2. Verify that the Deployment has been rolled back:

kubectl rollout status deployment/my-deployment

This will show you the status of the latest rollout of the my-deployment Deployment.

Clean Up

1. Delete the my-deployment Deployment:

kubectl delete deployment my-deployment

This will delete the my-deployment Deployment and its associated ReplicaSets and Pods.

Summary

In this lab, you learned how to create and manage Deployments in Kubernetes. You created a Deployment with 3 replicas, scaled the Deployment to 5 replicas, updated the Deployment to use a different image, rolled back the Deployment to the previous version,