Kubernetes Deployment Strategies

Deploying Java applications to Kubernetes requires understanding various deployment strategies.

Rolling Updates

The default strategy that gradually replaces old pods:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: order-service
spec:
  replicas: 3
  strategy:
    type: RollingUpdate
    rollingUpdate:
      maxSurge: 1
      maxUnavailable: 0

Blue-Green Deployments

Maintain two identical environments:

# Switch traffic by updating service selector
apiVersion: v1
kind: Service
metadata:
  name: order-service
spec:
  selector:
    app: order-service
    version: green  # Switch to blue for rollback

Canary Releases

Gradually shift traffic to new version using Istio:

apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
spec:
  http:
  - route:
    - destination:
        host: order-service
        subset: v1
      weight: 90
    - destination:
        host: order-service
        subset: v2
      weight: 10

Choose the strategy that best fits your risk tolerance and deployment frequency.