StatefulSet with Stable Pod Identity + Headless Service

The situation

You're deploying a clustered, stateful workload where peers must address each other by stable hostname (e.g. web-0.web, web-1.web). A Deployment + ClusterIP Service can't give that — you need a StatefulSet plus a headless Service (clusterIP: None) to publish per-pod DNS records.

  ┌────────────────────────────┐
  │Service web, clusterIP None │
  │                            │
  └────────────────────────────┘
        │             │         
    A record      A record      
        │             │         
        ▼             ▼         
 ┌────────────┐ ┌────────────┐  
 │ web-0.web  │ │ web-1.web  │  
 │            │ │            │  
 └────────────┘ └────────────┘

Your task

In namespace kubelings:

Create a headless Service named web (clusterIP: None) selecting app=web.
Create a StatefulSet named web with ≥ 2 replicas, serviceName: web, image ghcr.io/iximiuz/labs/nginx:alpine.
All replicas must be Ready (web-0, web-1, …).

kubectl -n kubelings get sts,svc,pods
kubectl -n kubelings exec web-0 -- nslookup web-1.web 2>/dev/null || true

Hint

The Service must come first and be headless; the StatefulSet's serviceName must point at it. See solution.md for a complete manifest.

Solution

Approach

Stable identity = StatefulSet + headless Service. The headless Service (clusterIP: None) makes the DNS plane publish web-N.web.<ns>.svc records; the StatefulSet's serviceName binds the two.

Create it

kubectl -n kubelings apply -f - <<'EOF'
apiVersion: v1
kind: Service
metadata:
  name: web
spec:
  clusterIP: None        # headless
  selector: {app: web}
  ports:
    - port: 80
      targetPort: 80
---
apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: web
spec:
  serviceName: web        # must match the headless Service
  replicas: 2
  selector:
    matchLabels: {app: web}
  template:
    metadata:
      labels: {app: web}
    spec:
      containers:
        - name: web
          image: ghcr.io/iximiuz/labs/nginx:alpine
          ports: [{containerPort: 80}]
          readinessProbe:
            httpGet: {path: /, port: 80}
            initialDelaySeconds: 1
            periodSeconds: 2
EOF

Verify

kubectl -n kubelings rollout status sts/web
kubectl -n kubelings get pods -l app=web        # web-0, web-1
kubectl -n kubelings exec web-0 -- nslookup web-1.web