Understanding kubernetes port forwarding, port and targetPort

So, this is my understanding that port is the port on which a service serves requests and targetPort is the port where your app within the container servers requests.

targetPort is not even required to be specified, it is usually the same as containerPort (I got this from a StackOverflow answer and I verified it by removing targetPort)

Kubernetes port forwarding forwards the request received on local port to the remote port (where the service runs). I have been following this article to understand this better

In my application, the specs were created using helm. My port is set to 80 and my containerPort is set to 5000 (It is a very simple Flask app).

Following the example mentioned in that link the following should work:

kubectl --namespace default port-forward $POD_NAME 7000:80  

but this one works instead:

kubectl --namespace default port-forward $POD_NAME 7000:5000  

Is there something I've not understood correctly? Here's the kubectl describe of my pod:

Name:           mock-python-server-9f5b557f5-klxq8  Namespace:      default  Priority:       0  Node:           docker-desktop/192.168.65.3  Start Time:     Thu, 21 Jan 2021 13:59:40 -0800  Labels:         app.kubernetes.io/instance=mock-python-server                  app.kubernetes.io/name=mock-python-server                  pod-template-hash=9f5b557f5  Annotations:    <none>  Status:         Running  IP:             10.1.2.39  Controlled By:  ReplicaSet/mock-python-server-9f5b557f5  Containers:    master:      Container ID:   docker://7e258d94c458f47c1add418c7969e77fbaa532c56df7405681e778d5f0e63d01      Image:          <image>      Image ID:       <image_id>      Port:           5000/TCP      Host Port:      0/TCP      State:          Running        Started:      Thu, 21 Jan 2021 13:59:43 -0800      Ready:          True      Restart Count:  0      Limits:        cpu:     100m        memory:  128Mi      Requests:        cpu:      100m        memory:   128Mi      Liveness:   http-get http://:http/health delay=0s timeout=1s period=10s #success=1 #failure=3      Readiness:  http-get http://:http/health delay=0s timeout=1s period=10s #success=1 #failure=3      Environment:        env:  LOCAL  ...  

Here's a snippet from deployment.yaml:

apiVersion: apps/v1  kind: Deployment  spec:    template:      spec:        containers:           ports:             - name: http               containerPort: 5000                protocol: TCP           livenessProbe:             httpGet:              path: /health               port: http           readinessProbe:             httpGet:               path: /health               port: http  

and my service.yaml:

apiVersion: v1  kind: Service  spec:    type:     ports:      - port: 80         targetPort: 5000        protocol: TCP        name: http  

Where am I going wrong?

https://stackoverflow.com/questions/65837023/understanding-kubernetes-port-forwarding-port-and-targetport January 22, 2021 at 07:01AM