External-dns: CoreDNS as a DNS provider

[mattymo]

CoreDNS is an alternative for on-prem deployments where google/aws are not available. It has some support as a Federation DNS backend now: https://github.com/kubernetes/kubernetes/blob/master/federation/pkg/dnsprovider/providers/coredns/coredns.go

Can it be added as a valid external DNS source as well?

[ideahitme]

Yes this is something we have in our future plans https://github.com/kubernetes-incubator/external-dns/blob/master/docs/initial-design.md

But we will probably focus on integrating with AWS and Google first and based on that we will evaluate the ways to integrate CoreDNS as a possible DNS provider

[mattymo]

Thanks for the quick reply! Exposing dns data to coredns is as simple as writing info to etcd, so I hope it's not a big challenge.

[linki]

CoreDNS already supports ingesting Kubernetes resources via one of its middlewares (https://github.com/coredns/coredns/tree/master/middleware/kubernetes) and exposes DNS records the way KubeDNS uses to.

I was wondering if ExternalDNS like features can be implemented as a CoreDNS middleware. It basically just has to understand ExternalDNS's annotation semantics and expose DNS records accordingly.

[lsjostro]

I've written a terraform provider for coredns which might inspire someone to add this feature here.
https://github.com/shelmangroup/terraform-coredns

When we have NodePort support I might give it a go.

[istalker2]

I took an opportunity to write CoreDNS provider, which also happens to be SkyDNS provider.
Here is my PR: https://github.com/kubernetes-incubator/external-dns/pull/246

Probably the same can be achieved by writing new CoreDNS middleware rather than external-dns provider, but I do believe that duplicating external-dns functionality elsewhere is not a step in the right direction.

[lsjostro]

@istalker2 awesome! 👊🏻

[pigmej]

btw. #246 was replaced by #253

[calder]

253 seems to have stalled.

[hjacobs]

@calder @istalker2 anybody interested in picking up the PR (#253)?

[cedvan]

Hi,

I am very interested in this feature. But need some documentation to use CoreDNS ...