Cloud / HELM Interview Questions
How do you implement zero-downtime deployments with Helm?
Zero-downtime deployments with Helm require combining Kubernetes features with Helm-specific strategies.
1. RollingUpdate strategy in deployment:
spec:
strategy:
type: RollingUpdate
rollingUpdate:
maxSurge: 25%
maxUnavailable: 0 # Critical for zero-downtime
minReadySeconds: 10
revisionHistoryLimit: 10
maxUnavailable: 0 ensures old pods keep running until new pods are ready.
2. Readiness and liveness probes:
readinessProbe:
httpGet:
path: /health
port: 8080
initialDelaySeconds: 5
periodSeconds: 5
failureThreshold: 3
successThreshold: 1
livenessProbe:
httpGet:
path: /health
port: 8080
initialDelaySeconds: 30
periodSeconds: 10
3. PodDisruptionBudget for voluntary disruptions:
apiVersion: policy/v1
kind: PodDisruptionBudget
metadata:
name: {{ include "myapp.fullname" . }}
spec:
minAvailable: 2
selector:
matchLabels:
{{- include "myapp.selectorLabels" . | nindent 6 }}
4. Helm upgrade flags for safety:
helm upgrade --install myapp ./chart \
--wait \
--timeout 5m \
--atomic \
--cleanup-on-fail
- --wait: Wait for all resources to be ready
- --atomic: Rollback on failure (v3 feature)
- --cleanup-on-fail: Remove failed resources
5. Pre-stop hooks for graceful shutdown:
spec:
containers:
- name: app
lifecycle:
preStop:
exec:
command: ["sh", "-c", "sleep 15 && nginx -s quit"]
6. Database migration strategies: - Pre-upgrade hooks for migrations before new version starts - Backward compatible schema changes only (add columns, don't drop) - Blue-green deployment pattern for major schema changes
7. Progressive delivery with Flagger/Argo Rollouts:
apiVersion: argoproj.io/v1alpha1
kind: Rollout
metadata:
name: myapp
spec:
strategy:
canary:
steps:
- setWeight: 25
- pause: {duration: 1m}
- setWeight: 50
- pause: {duration: 1m}
- setWeight: 100
8. Monitoring during deployment:
Monitor during rollout: kubectl rollout status deployment/myapp --watch
Check for errors: helm ls --all-namespaces | grep -E "failed|pending"
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