DNS Horizontal Autoscaler enables horizontal autoscaling feature for DNS service in Kubernetes clusters. This autoscaler runs as a Deployment. It collects cluster status from the APIServer, horizontally scales the number of DNS backends based on demand. Autoscaling parameters could be tuned by modifying the kube-dns-autoscaler ConfigMap in kube-system namespace.

Learn more about:

Usage: http://kubernetes.io/docs/tasks/administer-cluster/dns-horizontal-autoscaling/
Implementation: https://github.com/kubernetes-incubator/cluster-proportional-autoscaler/