Readiness probe based on service

Question

I have 2 pods and my application is based on a cluster i.e. application synchronizes with another pod to bring it up. Let us say in my example I am using appod1 and appod2 and the synchronization port is 8080.

I want the service for DNS to be resolved for these pod hostnames but I want to block the traffic from outside the apppod1 and appod2.

I can use a readiness probe but then the service doesn't have endpoints and I can't resolve the IP of the 2nd pod. If I can't resolve the IP of the 2nd pod from pod1 then I can't complete the configuration of these pods.

E.g.

App Statefulset definition

app1_sts.yaml
===

apiVersion: apps/v1
kind: StatefulSet
metadata:
  labels:
    cluster: appcluster
  name: app1
  namespace: app
spec:
  selector:
    matchLabels:
      cluster: appcluster
  serviceName: app1cluster
  template:
    metadata:
      labels:
        cluster: appcluster
    spec:
     containers:
       - name: app1-0
         image: localhost/linux:8
         imagePullPolicy: Always
         securityContext:
          privileged: false
         command: [/usr/sbin/init]
         ports:
         - containerPort: 8080
           name: appport
         readinessProbe:
            tcpSocket:
              port: 8080
            initialDelaySeconds: 120
            periodSeconds: 30
            failureThreshold: 20
         env:
         - name: container
           value: "true"
         - name: applist
           value: "app2-0"


app2_sts.yaml
====

apiVersion: apps/v1
kind: StatefulSet
metadata:
  labels:
    cluster: appcluster
  name: app2
  namespace: app
spec:
  selector:
    matchLabels:
      cluster: appcluster
  serviceName: app2cluster
  template:
    metadata:
      labels:
        cluster: appcluster
    spec:
     containers:
       - name: app2-0
         image: localhost/linux:8
         imagePullPolicy: Always
         securityContext:
          privileged: false
         command: [/usr/sbin/init]
         ports:
         - containerPort: 8080
           name: appport
         readinessProbe:
            tcpSocket:
              port: 8080
            initialDelaySeconds: 120
            periodSeconds: 30
            failureThreshold: 20
         env:
         - name: container
           value: "true"
         - name: applist
           value: "app1-0"

Create Statefulsets and check name resolution

[root@oper01 onprem]# kubectl get all -n app
NAME             READY   STATUS    RESTARTS        AGE
pod/app1-0       0/1     Running   0               8s
pod/app2-0       0/1     Running   0               22s


NAME                        READY   AGE
statefulset.apps/app1       0/1     49s
statefulset.apps/app2       0/1     22s



kubectl exec -i -t app1-0 /bin/bash -n app


[root@app1-0 ~]# nslookup app2-0
Server:         10.96.0.10
Address:        10.96.0.10#53

** server can't find app2-0: NXDOMAIN

[root@app1-0 ~]# nslookup app1-0
Server:         10.96.0.10
Address:        10.96.0.10#53

** server can't find app1-0: NXDOMAIN

[root@app1-0 ~]#

I understand the behavior of the readiness probe and I am using it as it helps me to make sure service should not resolve to app pods if port 8080 is down. However, I am unable to make out how can I complete the configuration as app pods need to resolve each other and they need their hostname and IPs to configure. DNS resolution can only happen once the service has end points. Is there a better way to handle this situation?