Summary - Service

Combine ClusterIP, NodePort and selector to write a Service.

Summary: Services

In this group:

A Service gives label-selected pods a stable IP and DNS name; it spreads traffic over the ready pods.
port is the service's port, targetPort the pod's; DNS: name.namespace.svc.cluster.local.
Types: ClusterIP (internal), NodePort (node port), LoadBalancer (cloud external IP), ExternalName (DNS alias).
Selector labels combine with AND; blue-green switching can be done by changing labels.
kubectl expose creates one quickly; if the EndpointSlice is empty, the selector doesn't match.

kubectl expose deploy web --port=80 --target-port=8080 --type=NodePort
kubectl get svc,endpointslices

Exercise Inspect the service

Write three commands: expose the web deployment with --port=80 --target-port=8080 --type=NodePort; show the web service in detail; list the pods with their labels.

Show example solution

kubectl expose deployment web --port=80 --target-port=8080 --type=NodePort
kubectl describe svc web
kubectl get pods --show-labels

Test yourself

You created a service but requests get no answer and the endpoint list is empty. What is the most likely cause?
- The selector doesn't match the pod labels
- Port 80 is forbidden
- DNS is off
- The service type is ClusterIP
Show answer

The selector doesn't match the pod labels — Compare the labels with kubectl get pods --show-labels.

Create the service with the NodePort type.

kubectl expose deploy web --port=80 --target-port=8080 ____=NodePort

Show answer

kubectl expose deploy web --port=80 --target-port=8080 --type=NodePort

Match the types.

ClusterIP

Internal communication
NodePort

Node IP:port
LoadBalancer

External IP
ExternalName

CNAME

Next lesson: What is a ConfigMap?

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