Skip to main content

Service

Best Practice Flow​

Commands
k get svc/service
k get endpoints

Need to add selectors for pod manually.

warning

The below will not use the pods' labels as selectors; instead it will assume selectors as app=redis.

kubectl create service clusterip redis --tcp=6379:6379 --dry-run=client -o yaml

Cross-ns Pod Service Reach​

Hostname format for cross namespace pod communication, hostname:

svcname.namespace.svc.cluster.local

Expose​

tip

Expose first, edit the service later, quicker. This will automatically use the pod's labels as selectors, but you cannot specify the node port. 

warning

When using kubectl expose with --type=NodePort, you cannot specify which port number will be used on the node - Kubernetes will automatically assign one from the 30000-32767 range. If you need a specific nodePort, you'll need to edit the YAML afterward.

kubectl expose pod redis --port=6379 --name redis-service --dry-run=client -o yaml
kubectl expose pod nginx --port=80 --name nginx-service --type=NodePort --dry-run=client -o yaml
  • NodePorts can only be between 30,000 - 32767
  • NodePort is superset of ClusterIP type.
apiVersion: v1
kind: Service
metadata:
  name: my-service
spec:
  type: NodePort # default is ClusterIP. Also can be LoadBalancer (cloud provided), or ExternalName to route outside (cname)
  selector:
    app: my-app
  ports:
    - port: 80        # Service port (inside cluster)
      targetPort: 8080  # Pod port
      nodePort: 30080   # Optional, otherwise auto-assigned

Local port forwarding​

Forwards port to from local machine (8080) to pod (80)

kubectl port-forward pod/nginx 8080:80
kubectl port-forward svc/<service-name> 8080:80

Headless Service​

  • If ClusterIP: None then a service is headless.
  • It returns the matchin pod IPs, without doing load balancing.
  • Works well with stateful sets
  • Direct pod communication with client side service discovery.

For Pods​

  • pod.spec.subdomain should match headless service name and pod.spec.hostname should have value.
  • But for deployments it won't work as multiple pods will get the same subdomain.

For StatefulSets​

pod.spec.serviceName should match the headless service name.