Kubernetes Services

Pods have ephemeral IP addresses. A Service provides a stable network endpoint in front of a set of pods, load balancing traffic across them.

How Services Work

Services use label selectors to find pods. Any pod with matching labels receives traffic:

selector:
  app: my-app      # routes to pods with this label

Kubernetes maintains an Endpoints object that tracks the IPs of matching pods automatically as pods are created and destroyed.

Service Types

ClusterIP (default)

Accessible only within the cluster. Used for internal service-to-service communication.

apiVersion: v1
kind: Service
metadata:
  name: my-app-service
spec:
  type: ClusterIP
  selector:
    app: my-app
  ports:
    - port: 80          # port the service listens on
      targetPort: 8080  # port on the pod

# Access from inside the cluster using DNS
curl http://my-app-service.default.svc.cluster.local
# Or within the same namespace:
curl http://my-app-service

NodePort

Exposes the service on a static port on every node. Accessible from outside the cluster at <NodeIP>:<NodePort>.

spec:
  type: NodePort
  selector:
    app: my-app
  ports:
    - port: 80
      targetPort: 8080
      nodePort: 30080   # must be 30000-32767

Useful for development and testing. Not recommended for production — prefer LoadBalancer or Ingress.

LoadBalancer

Provisions a cloud load balancer (AWS ELB, GCP LB, Azure LB) that routes traffic to the NodePort:

spec:
  type: LoadBalancer
  selector:
    app: my-app
  ports:
    - port: 80
      targetPort: 8080

The cloud provider assigns an external IP automatically. Each service gets its own load balancer, which can be costly — use Ingress to share one LB across multiple services.

ExternalName

Maps a service name to an external DNS name. No proxying — just DNS aliasing.

spec:
  type: ExternalName
  externalName: my.external-database.com

DNS Resolution

Kubernetes provides automatic DNS for services:

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

From the same namespace, just <service-name> works.

Multi-Port Services

ports:
  - name: http
    port: 80
    targetPort: 8080
  - name: https
    port: 443
    targetPort: 8443

Common Commands

kubectl get services
kubectl describe service my-app-service
kubectl delete service my-app-service

# Check which pods the service routes to
kubectl get endpoints my-app-service

Service vs Ingress

	Service (LoadBalancer)	Ingress
Cost	One LB per service	One LB for all services
Routing	Port-based	Path and host-based HTTP routing
TLS termination	At LB level	At Ingress level
Use for	Non-HTTP protocols, single service	HTTP/HTTPS with multiple services