coredns
CoreDNS is a single process, written in Go, that covers all of the functionality of the previous system. A single container resolves and caches DNS queries, responds to health checks, and provides metrics.

my-web-service.my-kube-namespace.svc.cluster.local

refer

The pods’ dns server is coredns in k8s,
/etc/resolv.conf
[service kube-dns cluster ip]

coredns config
config