KCD Porto 2025 - Achieving Zero-Downtime Deployments in Kubernetes"

zero_downtime_app.yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: server-deployment
  labels:
    app: MyApp
spec:
  replicas: 2
  selector:
    matchLabels:
      app: MyApp
  template:
    metadata:
      labels:
        app: MyApp
    spec:
      # This ensures pods try to run on different nodes for high availability
      affinity:
        podAntiAffinity:
          preferredDuringSchedulingIgnoredDuringExecution:
          - weight: 100
            podAffinityTerm:
              labelSelector:
                matchExpressions:
                - key: app
                  operator: In
                  values:
                  - MyApp
              topologyKey: "kubernetes.io/hostname"
      
      # This tells the pod it has 30 seconds to finish requests before being killed
      terminationGracePeriodSeconds: 30
      
      containers:
      - name: agnhost
        # This is the image that will be running
        image: k8s.gcr.io/e2e-test-images/agnhost:2.39
        args:
          - netexec
          - --http-port=80
          # This tells the app to wait 30s before exiting, to use the grace period
          - --delay-shutdown=30
        ports:
        - containerPort: 80
        # This Readiness Probe is critical for zero-downtime
        readinessProbe:
          httpGet:
            path: /
            port: 80
          initialDelaySeconds: 5
          periodSeconds: 5
---
apiVersion: v1
kind: Service
metadata:
  name: lb-service
spec:
  type: LoadBalancer
  # This setting is good for preserving client IPs
  externalTrafficPolicy: Local
  selector:
    app: MyApp
  ports:
    - protocol: TCP
      port: 80
      targetPort: 80
---
apiVersion: policy/v1
kind: PodDisruptionBudget
metadata:
  name: myapp-pdb
spec:
  # You can also use minAvailable: 1
  maxUnavailable: 1
  selector:
    matchLabels:
      app: MyApp

watch "kubectl get pods -l app=MyApp -o wide && echo '---' && kubectl get pdb myapp-pdb  && echo '---' && kubectl get replicaset"