Endpoints

Pods behind a service.

Lets describe the service to see how the mapping of Pods works in a service object.

(Yes , we are slowly moving from general wordings to pure kubernetes terms)

$ kubectl describe service coffee
Name:                     coffee
Namespace:                default
Labels:                   run=coffee
Annotations:              <none>
Selector:                 run=coffee
Type:                     NodePort
IP:                       192.168.10.86
Port:                     <unset>  80/TCP
TargetPort:               9090/TCP
NodePort:                 <unset>  30391/TCP
Endpoints:                10.10.1.13:9090
Session Affinity:         None
External Traffic Policy:  Cluster

Here the label run=coffee is the one which creates the mapping from service to Pod.

Any pod with label run=coffee will be mapped under this service.

Those mappings are called Endpoints.

Lets see the endpoints of service coffee

$ kubectl get endpoints  coffee
NAME     ENDPOINTS         AGE
coffee   10.10.1.13:9090   3h48m

As of now only one pod endpoint is mapped under this service.

lets create one more Pod with same label and see how it affects endpoints.

$ kubectl run coffee01 --image=ansilh/demo-coffee --restart=Never --labels=run=coffee

Now we have one more Pod

$ kubectl get pods
NAME       READY   STATUS    RESTARTS   AGE
coffee     1/1     Running   0          15h
coffee01   1/1     Running   0          6s

Lets check the endpoint

$ kubectl get endpoints  coffee
NAME     ENDPOINTS                         AGE
coffee   10.10.1.13:9090,10.10.1.19:9090   3h51m

Now we have two Pod endpoints mapped to this service. So the requests comes to coffee service will be served from these pods in a round robin fashion.