Kubernetes Services - Network Abstraction & Service Discovery Guide

Comprehensive guide to Kubernetes Services covering ClusterIP, NodePort, LoadBalancer types, label selectors, service discovery, and networking concepts with practical examples

What are Kubernetes Services?

A Service is a Kubernetes object that provides stable network access to a set of Pods. It acts as an abstraction layer that enables network access to Pods, which are ephemeral and dynamic by nature.

Stable Network Identity

Provides reliable IP addresses and DNS names unlike ephemeral Pod IPs

Durable & Reliable

Services persist while Pods come and go, ensuring continuous availability

Load Balancing

Automatically distributes traffic across multiple Pod instances

Key Benefit: Pod IPs are unreliable (they change when Pods restart or reschedule), but Service IPs are durable and stable throughout the Service's lifetime.

Label Selectors - How Services Find Pods

Services use label selectors to identify which Pods they should route traffic to. Only Pods with matching labels become endpoints of the Service.

Service
Selector: zone=prod version=v1
→
Pod
zone=prod
version=v1
Pod
zone=prod
version=v1
Pod
zone=prod
version=v2
Pod
zone=prod

Service Definition

apiVersion: v1
kind: Service
metadata:
  name: my-service
spec:
  selector:
    zone: prod
    version: v1
  ports:
    - protocol: TCP
      port: 80
      targetPort: 8080

Pod Labels

# Pod 1 & 2 (matched)
apiVersion: v1
kind: Pod
metadata:
  name: pod-1
  labels:
    zone: prod
    version: v1
spec:
  containers:
  - name: app
    image: my-app:v1

# Pod 3 (unmatched - wrong version)
apiVersion: v1
kind: Pod
metadata:
  name: pod-3
  labels:
    zone: prod
    version: v2  # Doesn't match selector

# Pod 4 (unmatched - missing label)
apiVersion: v1
kind: Pod
metadata:
  name: pod-4
  labels:
    zone: prod   # Missing version label

Selector Behavior

  • All selector labels must match exactly
  • Pods without all required labels are ignored
  • New Pods with matching labels automatically become endpoints
  • Terminated Pods are automatically removed from endpoints

Service Types

Kubernetes supports different Service types to accommodate various networking requirements and access patterns.

ClusterIP

Default service type. Exposes the service on a cluster-internal IP address.

  • Only accessible within the cluster
  • Ideal for inter-service communication
  • Most common service type
  • Secure internal networking
spec:
  type: ClusterIP
  ports:
  - port: 80

NodePort

Exposes the service on each Node's IP at a static port.

  • Accessible from outside the cluster
  • Opens a port on every cluster node
  • NodeIP:NodePort accesses the service
  • Good for development and testing
spec:
  type: NodePort
  ports:
  - port: 80
    targetPort: 8080
    nodePort: 30007

LoadBalancer

Creates an external load balancer in cloud providers.

  • Cloud provider integration
  • Automatic external IP assignment
  • Production-grade external access
  • Cloud-specific load balancing
spec:
  type: LoadBalancer
  ports:
  - port: 80
Service Type Access Scope Use Case Cloud Provider
ClusterIP Cluster Internal Microservices communication Not required
NodePort External via Node IP Development, testing Not required
LoadBalancer External via Load Balancer Production web services Required

Service Best Practices

Naming & Organization

  • Use descriptive service names that reflect their purpose
  • Follow consistent naming conventions across services
  • Use namespaces to organize services logically
  • Include version information in labels, not service names
  • Use DNS-friendly names (lowercase, hyphens instead of underscores)

Configuration & Security

  • Use ClusterIP for internal services to limit exposure
  • Implement Network Policies to control service access
  • Use meaningful port names for multi-port services
  • Configure appropriate session affinity if needed
  • Monitor service endpoints and health status

Common kubectl Commands for Services

# List all services
kubectl get services

# Get service details
kubectl describe service my-service

# Create service from file
kubectl apply -f service.yaml
# Get service endpoints
kubectl get endpoints my-service

# Delete service
kubectl delete service my-service

# Port forwarding
kubectl port-forward service/my-service 8080:80