Expose every replica pods in a deployment/replicaset with nodeport service - kubernetes

Question

I have 2 bare metal worker nodes and a replicaset with 10 pod replicas. How can I expose each pod using nodeport?

Answer 1

You can use the kubectl expose command to create a NodePort Service for a ReplicaSet.
This is a template that may be useful:
kubectl expose rs <REPLICASET_NAME> --port=<PORT> --target-port=<TARGET_PORT> --type=NodePort
The most important flags are:
NOTE: Detailed information on this command can be found in the Kubectl Reference Docs.
--port
The port that the service should serve on. Copied from the resource being exposed, if unspecified
--target-port
Name or number for the port on the container that the service should direct traffic to. Optional.
--type
Type for this service: ClusterIP, NodePort, LoadBalancer, or ExternalName. Default is 'ClusterIP'.
I will create an example to illustrate how it works
First, I created a simple app-1 ReplicaSet:
$ cat app-1-rs.yaml
apiVersion: apps/v1
kind: ReplicaSet
metadata:
name: app-1
labels:
app: app-1
spec:
replicas: 10
selector:
matchLabels:
app: app-1
template:
metadata:
labels:
app: app-1
spec:
containers:
- name: nginx
image: nginx
$ kubectl apply -f app-1-rs.yaml
replicaset.apps/app-1 created
$ kubectl get rs
NAME DESIRED CURRENT READY AGE
app-1 10 10 10 93s
Then I used the kubectl expose command to create a NodePort Service for the app-1 ReplicaSet:
### kubectl expose rs <REPLICASET_NAME> --port=<PORT> --target-port=<TARGET_PORT> --type=NodePort
$ kubectl expose rs app-1 --port=80 --type=NodePort
service/app-1 exposed
$ kubectl get svc app-1
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
app-1 NodePort 10.8.6.92 <none> 80:32275/TCP 18s
$ kubectl describe svc app-1 | grep -i endpoints
Endpoints: 10.4.0.15:80,10.4.0.16:80,10.4.0.17:80 + 7 more...
If you want to make some modifications before creating the Service, you can export the Service defintion to a manifest file and apply it after the modifications:
kubectl expose rs app-1 --port=80 --type=NodePort --dry-run=client -oyaml > app-1-svc.yaml
Additionally, it's worth considering if you can use Deployment instead of directly using ReplicaSet. As we can find in the Kubernetes ReplicaSet documentation:
Deployment is a higher-level concept that manages ReplicaSets and provides declarative updates to Pods along with a lot of other useful features. Therefore, we recommend using Deployments instead of directly using ReplicaSets, unless you require custom update orchestration or don't require updates at all.

Answer 2

you can create a service with selector point to the pods, use NodePort type, and be sure deploy kube-proxy on every node.
example yaml like below, you should set right selector and port. get service detail for nodePort after created
apiVersion: v1
kind: Service
metadata:
name: my-service
spec:
selector:
app: MyApp
type: NodePort
ports:
- name: http
protocol: TCP
port: 80
targetPort: 80
the official doc is good enough https://kubernetes.io/docs/concepts/services-networking/service/