The Service Registry

The job of a service registry is to maintain a list of Service names and their associated IP addresses. Apps use it to convert Service names into IP addresses.

Cluster DNS

Every Kubernetes cluster has a built-in cluster DNS that it uses as its service registry. It’s a Kubernetes-native application running on the control plane of every Kubernetes cluster as two or more Pods managed by a Deployment and fronted by a Service. The Deployment is usually called coredns or kube-dns, and the Service is always called kube-dns.

The following figure shows the service registry architecture. It also shows a Service registering its name and IP and two containers using it for service discovery. As you’ll find out later, service registration and service discovery are both automatic.