Deployments and Rolling Updates

Objective: The objective of this assignment is to gain practical experience in creating Kubernetes Deployments and performing rolling updates to a web application without causing downtime. You will create a Deployment for a web application and then update it to a new version seamlessly.

Scenario: Imagine you are a DevOps engineer working on a small live project that involves deploying a web application. Your team has decided to use Kubernetes Deployments for managing the application's lifecycle. In this assignment, you will perform rolling updates to the web application to introduce a new version while ensuring uninterrupted service.

Prerequisites: Before starting this assignment, ensure that you have access to a Kubernetes cluster, `kubectl` installed, and configured to work with your cluster.

 Below is a Kubernetes Deployment YAML manifest (`web-app-deployment.yaml`) for deploying a web application using the Nginx image with a version one level less than the latest. You can use this manifest as a template:

apiVersion: apps/v1

kind: Deployment

metadata:

  name: web-app-deployment

spec:

  replicas: 3

  selector:

    matchLabels:

      app: web-app

  template:

    metadata:

      labels:

        app: web-app

    spec:

      containers:

        - name: web-app-container

          image: nginx:1.21  # Specify the desired version (e.g., 1.21) here

          ports:

            - containerPort: 80

In this manifest:

- `apiVersion` specifies the Kubernetes API version for the Deployment.

- `kind` specifies that this is a Deployment resource.

- `metadata` includes metadata such as the name of the Deployment.

- `spec` defines the specification for the Deployment.

  - `replicas` specifies the desired number of replicas (in this case, 3).

  - `selector` defines the selector that matches the pods controlled by this Deployment.

  - `template` specifies the pod template used to create new pods.

    - `metadata` within the template defines labels for the pod.

    - `spec` within the template specifies the pod's specification.

      - `containers` lists the containers within the pod. There is one container named `web-app-container`.

        - `name` specifies the container's name.

        - `image` specifies the container image to use, with the desired version (e.g., `nginx:1.21`).

        - `ports` defines an array of port mappings, allowing port 80 to be exposed within the pod.

Replace `1.21` with the version you want to deploy, which is one level less than the latest version available.

Instructions:

Part 1: Create a Deployment

1. Write a Kubernetes Deployment YAML manifest (`web-app-deployment.yaml`) that defines a Deployment for a web application. Use the following specifications:

   - Use the latest container image for the web application.

   - Define resource requests and limits as appropriate.

   - Set the replicas to 3 for redundancy.

2. Use `kubectl apply` to create the Deployment in your Kubernetes cluster:

   

   kubectl apply -f web-app-deployment.yaml

   

3. Verify that the Deployment and its pods are created and running using `kubectl get deployment` and `kubectl get pods`.

Part 2: Perform a Rolling Update

1. Modify the Deployment YAML manifest (`web-app-deployment.yaml`) to specify an updated container image with a new version of the web application.

2. Use `kubectl apply` to apply the changes to the Deployment:

   

   kubectl apply -f web-app-deployment.yaml

   

3. Monitor the rolling update progress using `kubectl get pods` and observe how Kubernetes gradually replaces old pods with new ones.

4. Verify that the updated version of the web application is running successfully.

Part 3: Clean Up (Optional)

1. After completing the assignment and practicing Deployments and rolling updates, you can clean up the resources by deleting the Deployment:

   

   kubectl delete deployment <deployment-name>