Rolling Back a Kubernetes Deployment (Using Nginx)

Let's create a more comprehensive lab exercise for rolling back a Kubernetes Deployment using an Nginx image.

Table of Contents

  1. Introduction

  2. Prerequisites

  3. Step 1: Create a Deployment

  4. Step 2: Change Revision History

  5. Step 3: Update the Version

  6. Step 4: Check Rollout History

  7. Step 5: Roll Back to a Previous Revision

  8. Step 6: Verify Rollback Success

  9. Conclusion

Introduction

In this lab exercise, we'll walk through the process of rolling back a Kubernetes Deployment using an Nginx image. We'll create a Deployment, update its version, and then perform a rollback to a previous revision.

Step 1: Create a Deployment

  1. Create a Deployment with three replicas using the Nginx image (nginx:1.13.0). Below is an example of a Deployment YAML definition:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
spec:
  replicas: 3
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
        - name: nginx
          image: nginx:1.13.0

Apply the definition using:

kubectl apply -f nginx-deployment.yaml

Step 2: Change Revision History

Update the Deployment definition file (nginx-deployment.yaml) to set the revision history limit to 10. Add the following field under the spec section:

spec:
  revisionHistoryLimit: 10

Apply the updated Deployment:

kubectl apply -f nginx-deployment.yaml --record

Step 3: Update the Version

  1. Change the image version in nginx-deployment.yaml to a new version (e.g., nginx:2.0.0).

We'll start with version nginx:1.14.2, apply the change, then proceed to version nginx:1.16.1. We'll focus on the container spec section in the exercise.

Update to Nginx 1.14.2

  1. Open your existing nginx-deployment.yaml file.

  2. Locate the containers section under the spec of your Deployment.

  3. Update the image field to use nginx:1.14.2:

    spec:
  replicas: 3
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
        - name: nginx
          image: nginx:1.14.2
          ports:
            - containerPort: 80

  4. Apply the updated Deployment:

    kubectl apply -f nginx-deployment.yaml --record

  5. Observe the Pods being created and verify that they are running the specified Nginx version.

Update to Nginx 1.16.1

  1. Open the same nginx-deployment.yaml file.

  2. Modify the image field to use nginx:1.16.1:

    spec:
  containers:
    - name: nginx
      image: nginx:1.16.1
      ports:
        - containerPort: 80

  3. Apply the updated Deployment:

    kubectl apply -f nginx-deployment.yaml --record

  4. Again, observe the Pods as they roll out with the new Nginx version.

Remember to adjust the Deployment name and other details according to your environment.

Wait for the Pods to roll out and become healthy.

Try for some other version too

Here are the other version of nginx, you can try changing the version to have number of revision history.

nginx:1.23.4 nginx:1.23.2 nginx:1.23 nginx:1.19.6

Step 4: Check Rollout History

To view the rollout history, run:

kubectl rollout history deploy nginx-deployment

This command will display the revision history along with any change causes.

Step 5: Roll Back to a Previous Revision

To undo the current rollout and rollback to the previous revision, use:

kubectl rollout undo deploy nginx-deployment

Alternatively, you can specify a specific revision to roll back to using --to-revision:

kubectl rollout undo deploy nginx-deployment --to-revision=<revision-number>

Step 6: Verify Rollback Success

After rolling back, check if the Deployment is running as expected:

kubectl describe deploy nginx-deployment

Ensure that the Pods are healthy and the desired version (e.g., nginx:1.13.0) is deployed.

Conclusion

Rollbacks are essential for maintaining service stability. By following these steps, you can confidently manage deployments and handle rollbacks effectively.

Remember to replace <revision-number> with the actual revision you want to roll back to. Adjust the version numbers in your Deployment definition file as needed.

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