what is the best way to access a web app running in aks container from outside the cluster with a name, which is already defined in Azure DNS zone? and an external DNS server can be helpful for this?
I would setup an ingress that would point to your service which exposes the web app.
apiVersion: networking.k8s.io/v1beta1
kind: Ingress
metadata:
name: simple-fanout-example
annotations:
nginx.ingress.kubernetes.io/rewrite-target: /
spec:
rules:
- host: your.web.app.address
http:
paths:
- path: /
backend:
serviceName: service
servicePort: 8080
Ingress exposes HTTP and HTTPS routes from outside the cluster to services within the cluster. Traffic routing is controlled by rules defined on the Ingress resource.
internet
|
[ Ingress ]
--|-----|--
[ Services ]
An Ingress may be configured to give Services externally-reachable URLs, load balance traffic, terminate SSL / TLS, and offer name based virtual hosting. An Ingress controller is responsible for fulfilling the Ingress, usually with a load balancer, though it may also configure your edge router or additional frontends to help handle the traffic.
An Ingress does not expose arbitrary ports or protocols. Exposing services other than HTTP and HTTPS to the internet typically uses a service of type Service.Type=NodePort or Service.Type=LoadBalancer.
I would recommend reading Create an ingress controller in Azure Kubernetes Service (AKS), or use Azure Application Gateway as an ingress this is explained here and you can find tutorials on GitHub