Why is my service always routing to the same pod?

Question

I have a simple Webserver that exposes the pod name on which it is located by using the OUT env var.

Deployment and service look like this:

apiVersion: v1
kind: Service
metadata:
  name: simpleweb-service
spec:
  selector:
    app: simpleweb
  ports:
    - protocol: TCP
      port: 8080
      targetPort: 8080
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: simpleweb-deployment
  labels:
    app: simpleweb
spec:
  replicas: 3
  selector:
    matchLabels:
      app: simpleweb
  template:
    metadata:
      labels:
        app: simpleweb
    spec:
      containers:
      - name: simpleweb
        env:
          - name: OUT
            valueFrom:
              fieldRef:
                fieldPath: metadata.name
        imagePullPolicy: Never
        image: simpleweb
        ports:
        - containerPort: 8080

I deploy this on my local kind cluster

default   simpleweb-deployment-5465f84584-m59n5 1/1     Running   0   12m
default   simpleweb-deployment-5465f84584-mw8vj 1/1     Running   0   9m36s
default   simpleweb-deployment-5465f84584-x6n74 1/1     Running   0   12m

and access it via

kubectl port-forward service/simpleweb-service 8080:8080

When I am hitting localhost:8080 I always get to the same pod

Questions:

Is my service not doing round robin?
Is there some caching that I am not aware of
Do I have to expose my service differently? Is this a kind issue?

Does this answer your question? [Does kubectl port-forward ignore loadBalance services?](https://stackoverflow.com/questions/59940833/does-kubectl-port-forward-ignore-loadbalance-services) — Andrew, Nov 03 '22 at 11:58

score 1 · Answer 1 · answered Nov 03 '22 at 18:52

port-forward will only select the first pod for a service selector. If you want round-robin you'd need to use a load balancer like traefik or nginx.

https://github.com/kubernetes/kubectl/blob/652881798563c00c1895ded6ced819030bfaa4d7/pkg/polymorphichelpers/attachablepodforobject.go#L52

score 1 · Answer 2 · answered Nov 04 '22 at 08:16

To do round-robin and route to different services I have to use a LoadBalancer service. There is MetalLB that implements a LB for Kind. Unfortunately it currently does not support Apply M1 machines.

I assume that MetallLB + LoadBalancer Service would work on a different machine.

Why is my service always routing to the same pod?

2 Answers2