Unless you say otherwise, a Service is a ClusterIP Service: reachable from inside the cluster, and only from there.

A virtual IP

learner@shallows:~$ kubectl get svc market-web
NAME         TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)   AGE
market-web   ClusterIP   10.96.248.109   <none>        80/TCP    5s

10.96.248.109 is not a machine. No container listens on it. It is an address that every node knows how to rewrite.

kube-proxy, the third program on every node from Chapter 2, watches Services and programs the node's packet rules. A packet to the cluster IP leaves the node already addressed to a Pod. Three Pods behind the Service share the traffic.

Reach it

From a Pod, the Service answers by name or by IP:

learner@shallows:~$ kubectl exec client -- wget -qO- market-web
<!doctype html>
<html>
<head><title>Monster Market</title></head>

From your own terminal the name means nothing; curl http://market-web fails. The cluster IP is inside the cluster.

Service port

expose --port=8080 sets the port clients use. For now it is also the port on the Pod; the lesson after next separates the two.

learner@shallows:~$ kubectl expose deployment market-api --port=8080
service/market-api exposed
learner@shallows:~$ kubectl exec client -- wget -qO- market-api:8080/healthz
{"status":"ok"}