Service discovery and DNS overview

This topic describes how GKE on Azure interacts with Domain Name Services (DNS).

Service discovery

Service discovery is the process where workloads discover services without knowing the service's IP address. This section describes how GKE on Azure implements service discovery and managed DNS.

Kubernetes automatically generates service names that use the following specification :

service . namespace .svc.cluster.local

Where:

• service : your service's name
• namespace : your service's Namespace

Workloads also access external services— for example example.net — using DNS names. For more information on the behavior of DNS in Kubernetes, see DNS for Services and Pods .

CoreDNS

GKE on Azure uses CoreDNS to resolve DNS names within clusters. CoreDNS runs as a redundant, scaled Deployment in the kube-system namespace. The CoreDNS deployment has a Service that groups the CoreDNS Pods and gives them a single IP address. The CoreDNS Deployment scales with the cluster's size and usage.

NodeLocal DNSCache

GKE on Azure uses NodeLocal DNSCache to improve DNS lookup performance. NodeLocal DNSCache runs as a DaemonSet on each node in your cluster. When a Pod makes a DNS request, the request first goes to the DNS cache on the same node. If the cache can't resolve the DNS request, the cache forwards the request to either:

• CoreDNS for an internal name— for example foo.bar.svc.cluster.local

What's next

• For an overview of how DNS is used in Kubernetes clusters, see DNS for Services and Pods .