Demo Endpoints and Endpoint Slices

In this tutorial, we’ll explore how Kubernetes manages Endpoints and Endpoint Slices by deploying a simple Nginx application. You’ll learn how to inspect the Endpoints resource, watch automatic updates as you scale Pods, and examine the more scalable Endpoint Slices feature introduced in Kubernetes 1.17.

1. Deploy Nginx and Inspect Endpoints

1.1 Verify Deployment and Service

First, create an Nginx Deployment and a ClusterIP Service (assumed already applied). Then confirm they’re up and running:

kubectl get deployments.apps

NAME                READY   UP-TO-DATE   AVAILABLE   AGE
nginx-deployment    1/1     1            1           5m

kubectl get services

NAME            TYPE        CLUSTER-IP       EXTERNAL-IP   PORT(S)    AGE
kubernetes      ClusterIP   10.96.0.1        <none>        443/TCP    40m
nginx-service   ClusterIP   10.98.220.254    <none>        80/TCP     5m

1.2 List Endpoints

Kubernetes automatically creates an Endpoints object that tracks the Pod IPs behind a Service:

kubectl get endpoints

NAME            ENDPOINTS            AGE
kubernetes      192.168.121.182:6443 40m
nginx-service   10.0.0.55:80         5m

1.3 Inspect the Endpoints Resource

View the full Endpoints object:

kubectl get endpoints nginx-service -o yaml

apiVersion: v1
kind: Endpoints
metadata:
  name: nginx-service
  namespace: default
subsets:
- addresses:
  - ip: 10.0.0.55
    nodeName: node01
    targetRef:
      kind: Pod
      name: nginx-deployment-7c79c4bf97-z79j4
      namespace: default
  ports:
  - name: nginx
    port: 80
    protocol: TCP

Alternatively, use describe for a concise summary:

kubectl describe endpoints nginx-service

Name:         nginx-service
Namespace:    default
Subset:
  Addresses:  10.0.0.55
  Ports:
    Name   Port  Protocol
    nginx  80    TCP

2. Scaling and Endpoint Updates

Kubernetes updates the Endpoints list automatically when Pods are added or removed.

1. Scale to two replicas:

   kubectl scale deployment nginx-deployment --replicas=2
   

2. Wait for both Pods to be Running:

   kubectl get pods
   

3. Describe Endpoints again:

   kubectl describe endpoints nginx-service
   

   Subset:
     Addresses: 10.0.0.55,10.0.1.248
     Ports:
       Name   Port  Protocol
       nginx  80    TCP
   

4. Delete one Pod and observe the update:

   kubectl delete pod nginx-deployment-7c79c4bf97-xd2mw
   kubectl describe endpoints nginx-service
   

5. Scale back to one replica:

   kubectl scale deployment nginx-deployment --replicas=1
   kubectl describe endpoints nginx-service
   

3. Exploring Endpoint Slices

Endpoint Slices improve scalability by splitting Service backends into multiple slice objects.

3.1 List Endpoint Slices

kubectl get endpointslices

NAME                         ADDRESSTYPE   PORTS  ENDPOINTS       AGE
kubernetes                   IPv4          6443   192.168.121.182 42m
nginx-service-87c5j          IPv4          80     10.0.0.55       7m

3.2 Inspect a Single EndpointSlice

kubectl get endpointslice nginx-service-87c5j -o yaml

apiVersion: discovery.k8s.io/v1
kind: EndpointSlice
metadata:
  name: nginx-service-87c5j
  namespace: default
  labels:
    kubernetes.io/service-name: nginx-service
    endpointslice.kubernetes.io/managed-by: endpointslice-controller.k8s.io
ports:
- name: nginx
  port: 80
  protocol: TCP
endpoints:
- addresses:
  - 10.0.0.55
  conditions:
    ready: true
  targetRef:
    kind: Pod
    name: nginx-deployment-7c79c4bf97-z79j4
  nodeName: node01

Or use:

kubectl describe endpointslice nginx-service-87c5j

Name:         nginx-service-87c5j
AddressType:  IPv4
Ports:
  Name   Port  Protocol
  nginx  80    TCP
Endpoints:
  - Addresses:   10.0.0.55
    Conditions:
      Ready:     true
    TargetRef:   Pod/nginx-deployment-7c79c4bf97-z79j4
    NodeName:    node01

3.3 EndpointSlice Updates on Scaling

Scale to two replicas:

kubectl scale deployment nginx-deployment --replicas=2
kubectl describe endpointslice nginx-service-87c5j

Endpoints:
  - Addresses: 10.0.0.55
    Conditions:
      Ready: true
    TargetRef: Pod/nginx-deployment-7c79c4bf97-z79j4
  - Addresses: 10.1.0.202
    Conditions:
      Ready: true
    TargetRef: Pod/nginx-deployment-7c79c4bf97-gsc44

Scale back to one replica and verify:

kubectl scale deployment nginx-deployment --replicas=1
kubectl describe endpointslice nginx-service-87c5j

Endpoints:
  - Addresses: 10.0.0.55
    Conditions:
      Ready: true
    TargetRef: Pod/nginx-deployment-7c79c4bf97-z79j4

4. Comparison and Conclusion

Kubernetes manages both Endpoints and Endpoint Slices automatically. Use Endpoints for small clusters and Endpoint Slices to handle large-scale Service connectivity efficiently.

Links and References

• Kubernetes Endpoints Concept
• Endpoint Slice Documentation
• Nginx on Kubernetes