Confused by the port names in k8s manifest

Question

I am confused by port name in manifest, for example, I see a manifest containing the following section:

ports:
  - name: web
    nodePort: 32003
    port: 80
    protocol: TCP
    targetPort: web
  - name: websecure
    nodePort: 30554
    port: 443
    protocol: TCP
    targetPort: websecure

What port number does the targetPort: web refers to exactly for the web name port? Same question for the targetPort: websecure. Could someone please elaborate for me?

A Service can map any incoming port to a targetPort. By default and for convenience, the targetPort is set to the same value as the port field. So websecure = 443, web = 80. Port definitions in Pods have names, and you can reference these names in the targetPort attribute of a Service, so if you don't have the port in the service, you can check the pod port definition. — char, Mar 23 '23 at 12:29

score 0 · Answer 1 · answered Mar 23 '23 at 15:12

The Pod specification can include ports: and these also can include a name:. So in this case the Service's ports: [{ name: }] needs to match the Pod's ports: [{ name: }].

# in the Pod spec, often in a Deployment object
ports:
  - containerPort: 8080
    name: web

This setup insulates you a little bit from knowing what the actual port is. Different frameworks use different ports by default (3000, 4000, 5000, 8000, 8080 all show up in various places) and just using a name here makes it easier to be consistent.

If you use a numeric Service port number, there's no particular requirement that the Pod declares the port, though the process inside the container still must be listening on that port.

The Service's port and the Pod's port don't need to agree and I often find it convenient to set Services to listen on the default port for their protocol – TCP port 80 for unencrypted HTTP – to avoid having to manually state a port number in connections between components.

(If you are using the Istio service mesh in particular, it wants the Service port names to match standard protocol names, so I might use http and https in this example. But the specific names don't really matter beyond this.)

Confused by the port names in k8s manifest

1 Answers1