Services can't communicate because there is not DNS resolving in Kubernetes - kubernetes

Question

I configure my services with type ClusterIP. And I want to make them communicated.
Service
apiVersion: v1
kind: Service
metadata:
labels:
app: app-backend-deployment
name: app-backend
spec:
type: ClusterIP
ports:
- port: 8020
protocol: TCP
targetPort: 8100
selector:
app: app-backend
Deployment
apiVersion: apps/v1
kind: Deployment
metadata:
labels:
app: app-backend
name: app-backend-deployment
spec:
replicas: 1
selector:
matchLabels:
app: app-backend
template:
metadata:
labels:
app: app-backend
spec:
containers:
- name: app-backend
image: app-backend
ports:
- containerPort: 8100
imagePullPolicy: Never
ConfigMap
apiVersion: v1
kind: ConfigMap
metadata:
name: backend-conf # name of configMap
data:
BACKEND_SERVICE_HOST: app-backend:8020
And that is what I pass to the frontend service, and I want to make a REST call through the DNS name for example http://app-backend:8020/get/1. But like I see in the console app cannot resolve DNS name net::ERR_NAME_NOT_RESOLVED.
I also check pod nslookup:
busybox nslookup app-backend.default.svc.cluster.local
Server: 10.96.0.10
Address: 10.96.0.10:53
Name: app-backend.default.svc.cluster.local
Address: 10.106.41.36
And compare it to
kubectl describe svc app-backend
Name: app-backend
Namespace: default
Labels: app=app-backend-deployment
Annotations: kubectl.kubernetes.io/last-applied-configuration:
{"...
Selector: app=app-backend
Type: ClusterIP
IP: 10.106.41.36
Port: <unset> 8020/TCP
TargetPort: 8100/TCP
And like you can see there is the same IP on Address but I don't know and where to look what is wrong why dns resolver doesn't work. kubectl version Client "v1.15.5", Server Version:"v1.17.3",

Answer 1

Because of that frontend service that was served to the local machine (that how Angular works) REST request cannot go through Kubernetes DNS with another backend service. I need to communicate them through the Ingress. Due to different annotations, I have to use 2 Ingress. Meaby there is a better way to use just one, but when I want to use only one Ingress I can't find a way to make them both working, with the same annotation.
apiVersion: extensions/v1beta1
kind: Ingress
metadata:
annotations:
kubernetes.io/ingress.class: nginx
nginx.ingress.kubernetes.io/rewrite-target: /$2
name: app-backend-ingress
spec:
rules:
- host: app.io
http:
paths:
- path: /api(/|$)(.*)
backend:
serviceName: app-backend
servicePort: 8020
---
apiVersion: extensions/v1beta1
kind: Ingress
metadata:
annotations:
kubernetes.io/ingress.class: nginx
nginx.ingress.kubernetes.io/rewrite-target: /
name: app-frontend-ingress
spec:
rules:
- host: app.io
http:
paths:
- path: /
backend:
serviceName: app-frontend
servicePort: 80