Demo Managing a rolling update on GKE cluster

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

1. Configure and Create the Cluster

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

# 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

2. Deploy a Simple Nginx Application

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

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:

kubectl apply -f gke-deep-dive-app.yaml
kubectl get deployments
kubectl get pods

3. Perform Rolling Updates

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

3.1 Update to Nginx 1.9.1

kubectl set image deployment/nginx-deployment nginx=nginx:1.9.1
kubectl rollout status deployment/nginx-deployment

Verify the new pods are running:

kubectl get pods

3.2 Update to Nginx 1.21.0

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

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

kubectl rollout undo deployment/nginx-deployment
kubectl describe deployment/nginx-deployment | grep Image

4.2 Rollback to a Specific Revision

1. View rollout history:

   kubectl rollout history deployment/nginx-deployment
   

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

   kubectl rollout undo deployment/nginx-deployment --to-revision=1
   kubectl describe deployment/nginx-deployment | grep Image
   

Links and References

• GKE Documentation
• Kubernetes Deployments
• kubectl Rollout
• Nginx Docker Hub