Use Cluster Proportional Autoscaler for CoreDNS 1.12+

[gjtempleton]

Follow the example of Kube-DNS for scaling the CoreDNS deployment by use of a cluster proportional autoscaler. Also adds a 10% maxSurge tolerance.

YAML added is near identical to the existing CPA and associate roles etc. used in https://github.com/kubernetes/kops/blob/master/upup/models/cloudup/resources/addons/kube-dns.addons.k8s.io/k8s-1.12.yaml.template

Mutually exclusive with #6797

[k8s-ci-robot]

Hi @gjtempleton. Thanks for your PR.

I'm waiting for a kubernetes member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

I understand the commands that are listed here.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[zetaab]

should this configmap exist?

[gjtempleton]

No, the proportional autoscaler creates it itself, that's why the ClusterRole has the ability to create configmaps within it.

kubernetes-sigs/cluster-proportional-autoscaler#16 has been closed due to staleness, so don't see this being resolved soon.

[zetaab]

/ok-to-test

[justinsb]

Looks great! Upstream is here https://github.com/kubernetes/kubernetes/blob/master/cluster/addons/dns-horizontal-autoscaler/dns-horizontal-autoscaler.yaml and it uses the kube-dns-autoscaler name, but that just seems wrong - it means we couldn't allow kube-dns and coredns to coexist, for example.

/approve
/lgtm

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: gjtempleton, justinsb

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [justinsb]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment