> ## Documentation Index
> Fetch the complete documentation index at: https://notes.kodekloud.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Demo Managing a rolling update on GKE cluster

> This tutorial teaches how to manage rolling updates on a GKE cluster, ensuring zero downtime and safe rollbacks.

In this tutorial, you’ll learn how to perform and manage rolling updates on a Google Kubernetes Engine (GKE) cluster. These concepts apply equally to upstream Kubernetes, enabling you to update container images with zero downtime and perform safe rollbacks when needed.

## Prerequisites

* Google Cloud SDK with `gcloud` and `kubectl` installed
* A Google Cloud project with billing enabled
* [Enable the Kubernetes Engine API](https://console.cloud.google.com/apis/library/container.googleapis.com)

***

## 1. Configure and Create the Cluster

First, set your Compute Engine zone and create a single-node GKE cluster named `gke-deep-dive`.

```bash theme={null}
# Set your desired zone
gcloud config set compute/zone us-west1-a

# Create a cluster with one node
gcloud container clusters create gke-deep-dive \
  --num-nodes=1 \
  --machine-type=e2-medium \
  --disk-type=pd-standard \
  --disk-size=10
```

<Callout icon="lightbulb" color="#1CB2FE">
  Cluster provisioning can take a few minutes. You can monitor progress in the Google Cloud Console under Kubernetes Engine > Clusters.
</Callout>

***

## 2. Deploy a Simple Nginx Application

Create a Deployment manifest `gke-deep-dive-app.yaml` with two replicas of Nginx:

```yaml theme={null}
apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
spec:
  replicas: 2
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: nginx:1.7.9
        ports:
        - containerPort: 80
```

Apply the manifest and verify the pods:

```bash theme={null}
kubectl apply -f gke-deep-dive-app.yaml
kubectl get deployments
kubectl get pods
```

| RESOURCE TYPE | COMMAND                                   | DESCRIPTION                        |
| ------------- | ----------------------------------------- | ---------------------------------- |
| Deployment    | `kubectl apply -f gke-deep-dive-app.yaml` | Create or update the deployment    |
| Pods          | `kubectl get pods`                        | List running pods and their status |

***

## 3. Perform Rolling Updates

GKE supports in-place rolling updates, ensuring that at least one replica remains available while others are replaced.

| Action          | Command                                                           | Description                         |
| --------------- | ----------------------------------------------------------------- | ----------------------------------- |
| Update image    | `kubectl set image deployment/nginx-deployment nginx=nginx:1.9.1` | Change the container image to 1.9.1 |
| Monitor rollout | `kubectl rollout status deployment/nginx-deployment`              | Wait until the rollout completes    |

### 3.1 Update to Nginx 1.9.1

```bash theme={null}
kubectl set image deployment/nginx-deployment nginx=nginx:1.9.1
kubectl rollout status deployment/nginx-deployment
```

Verify the new pods are running:

```bash theme={null}
kubectl get pods
```

### 3.2 Update to Nginx 1.21.0

Perform another image update to observe an in-progress rollout:

```bash theme={null}
kubectl set image deployment/nginx-deployment nginx=nginx:1.21.0
kubectl rollout status deployment/nginx-deployment
```

***

## 4. Rollback a Deployment

If a rollout introduces an issue, you can revert to a previous revision.

### 4.1 Rollback to the Previous Revision

```bash theme={null}
kubectl rollout undo deployment/nginx-deployment
kubectl describe deployment/nginx-deployment | grep Image
```

### 4.2 Rollback to a Specific Revision

1. View rollout history:

   ```bash theme={null}
   kubectl rollout history deployment/nginx-deployment
   ```

2. Roll back to revision 1 (original version):

   ```bash theme={null}
   kubectl rollout undo deployment/nginx-deployment --to-revision=1
   kubectl describe deployment/nginx-deployment | grep Image
   ```

<Callout icon="triangle-alert" color="#FF6B6B">
  Rolling back to a previous revision may disrupt your application. Always test in a staging environment before rolling back in production.
</Callout>

***

## Links and References

* [GKE Documentation](https://cloud.google.com/kubernetes-engine/docs)
* [Kubernetes Deployments](https://kubernetes.io/docs/concepts/workloads/controllers/deployment/)
* [kubectl Rollout](https://kubernetes.io/docs/reference/generated/kubectl/kubectl-commands#rollout)
* [Nginx Docker Hub](https://hub.docker.com/_/nginx)

<CardGroup>
  <Card title="Watch Video" icon="video" cta="Learn more" href="https://learn.kodekloud.com/user/courses/gke-google-kubernetes-engine/module/12020a5d-e2fd-46b5-82fb-35aa9cd57ad6/lesson/1890a557-b949-417a-bcab-3faad7e84049" />
</CardGroup>