Rolling Updates and Rollbacks in Kubernetes

Rolling updates and rollbacks are essential features in Kubernetes that allow you to update applications without downtime and revert to previous versions if necessary.

Rollout Commands

Kubernetes provides several commands to manage rollouts:

# Check the status of a rollout
kubectl rollout status deployment/my-deployment 
# Pause a rollout
kubectl rollout pause deployment/my-deployment
# Resume a paused rollout
kubectl rollout resume deployment/my-deployment
# Undo a rollout to the previous version
kubectl rollout undo deployment/my-deployment
# View the history of rollouts
kubectl rollout history deployment/my-deployment

Deployment Strategy

Kubernetes supports different deployment strategies, including:

• Rolling Update: Gradually replaces old pods with new ones, ensuring that some pods are always available.
• Recreate: Terminates all old pods before creating new ones, which can lead to downtime.
• Blue-Green Deployment: Maintains two separate environments (blue and green) to switch traffic between them during updates.

Kubectl apply

The kubectl apply command is used to update resources in Kubernetes. It applies changes to the current state of the cluster based on the provided configuration files.

# Apply changes to a deployment
kubectl apply -f deployment.yaml
# Apply changes to a service
kubectl apply -f service.yaml

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-container
        image: my-image:latest
        ports:
        - containerPort: 80
      strategy:
        type: RollingUpdate
        rollingUpdate:
          maxSurge: 1
          maxUnavailable: 1