Allow CoreDNS resources to be configured

[dominicgunn]

Changes

• Allows CoreDNS resources to be configured through cluster.yaml.

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Codecov Report

❗ No coverage uploaded for pull request base (master@eeb3f4e). Click here to learn what that means.
The diff coverage is 0%.

@@            Coverage Diff            @@
##             master    #1727   +/-   ##
=========================================
  Coverage          ?   25.28%           
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  Files             ?       98           
  Lines             ?     5087           
  Branches          ?        0           
=========================================
  Hits              ?     1286           
  Misses            ?     3659           
  Partials          ?      142

Impacted Files	Coverage Δ
pkg/api/types.go	0% <ø> (ø)
pkg/api/cluster.go	0% <0%> (ø)

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[davidmccormick]

/lgtm

[davidmccormick]

One last question! The dns resource sizing should be being governed on the fly by the dns-autoscaler pod - which is responsible for tweaking resource values and increasing the number of replicas in answer to the size of the cluster. Can you check to see what it is doing in your cluster? I would have hoped it would have been trying to scale it...

[dominicgunn]

I can see it scaling the number of pods, but cannot see it scaling resources for the pods. Should it be?

05 21:10:48.636587       1 k8sclient.go:250] Cluster status: SchedulableNodes[33], SchedulableCores[280]
I0905 21:10:48.636607       1 k8sclient.go:251] Replicas are not as expected : updating replicas from 2 to 3
I0905 21:20:38.626543       1 k8sclient.go:250] Cluster status: SchedulableNodes[32], SchedulableCores[276]
I0905 21:20:38.626562       1 k8sclient.go:251] Replicas are not as expected : updating replicas from 3 to 2

[davidmccormick]

@dominicgunn you are right, it only scales the number of replicas - so it sounds like your changes here are therefore super useful!