Design

Cant use a configmap to pass data from zoneforge to coredns since they are read only

Probably need to get into CRDs and a controller or operator design?

Design:

zoneforge writes to a CRD resource via k8s api.
- resource=zone, has a records key (array). Each record has discreet fields that map to zoneforge objects
controller component (separate?)
- watches for new CRD resources
- manages a configmap (one per zone?) of zone files for coredns

Problems:

if zoneforge is writing config to CRD resources, whats the source of truth?
- kubernetes resourceVersion is the answer, we get concurrency conflict handling for free
  - load zone by pulling CRD resource. if out of date, k8s api wouldnt let us save
  - https://kubernetes.io/docs/reference/using-api/api-concepts/#resource-versions
coredns reloading data
- by default, coredns will only reload a file source every 60s.
- kubelets will only refresh the configmap every 60-90s + jitter
- this is probably okay to have as an issue initially
- could write a custom CoreDNS plugin to solve this long term (pull from CRDs/k8s api not configmap mount)
  - https://coredns.io/2017/03/01/how-to-add-plugins-to-coredns/
  - could we watch each zone resource to immediate update?

Resources:

investigate kubernetes integration #94