Headless Services

A regular Service provides a single stable virtual IP (ClusterIP) that load-balances across all matching Pods. You send traffic to the ClusterIP, and kube-proxy distributes it. Individual Pods are hidden behind the virtual IP.

A headless Service has clusterIP: None. There is no virtual IP. Instead, DNS returns the actual IP addresses of each matching Pod directly. For StatefulSets, DNS returns one record per Pod, using the Pod’s stable name. This enables direct Pod-to-Pod addressing that survives restarts.

Creating a headless Service

The only difference from a regular Service is clusterIP: None:

apiVersion: v1
kind: Service
metadata:
  name: web-headless
spec:
  clusterIP: None
  selector:
    app: web
  ports:
    - port: 80
      name: web

kubectl get service web-headless

The CLUSTER-IP column shows None. There is no virtual IP for this service.

DNS for StatefulSet Pods

When a headless Service is paired with a StatefulSet via serviceName, each Pod gets its own DNS A record:

<pod-name>.<service-name>.<namespace>.svc.cluster.local

For our web StatefulSet with serviceName: web-headless in the default namespace:

• web-0.web-headless.default.svc.cluster.local resolves to the IP of web-0
• web-1.web-headless.default.svc.cluster.local resolves to the IP of web-1
• web-2.web-headless.default.svc.cluster.local resolves to the IP of web-2

Test DNS resolution from inside a Pod:

kubectl exec web-0 -- nslookup web-1.web-headless.default.svc.cluster.local

This returns the actual IP of web-1. If web-1 restarts and gets a new IP, the DNS record updates to the new IP automatically. The DNS name web-1.web-headless... remains stable even as the underlying IP changes.

DNS for the entire StatefulSet

A DNS query for just the Service name (without a Pod prefix) on a headless Service returns all Pod IPs:

kubectl exec web-0 -- nslookup web-headless

This returns multiple A records, one for each ready Pod. This is useful for initial cluster discovery: a new node can find all existing members by querying the service name, then communicate with specific members by their individual names.

This contrasts with a regular ClusterIP Service, where nslookup web-regular returns only the single ClusterIP, hiding the individual Pods.

Regular Service alongside headless Service

StatefulSets often use both types of Services:

• Headless Service (used as serviceName): provides stable per-Pod DNS, used by cluster members to communicate with each other
• Regular ClusterIP or NodePort Service: provides a load-balanced endpoint for clients that do not need to reach a specific Pod (e.g., read traffic to any replica)

# Regular Service for client access (routes to any ready Pod)
apiVersion: v1
kind: Service
metadata:
  name: web
spec:
  selector:
    app: web
  ports:
    - port: 80

With both Services, clients connect to web (load-balanced), while cluster nodes communicate via web-0.web-headless, web-1.web-headless, etc.

The headless Service is the bridge between the StatefulSet’s stable Pod names and stable network addressing. The next lesson covers how StatefulSets manage persistent storage with dedicated PVCs for each Pod.