Adding nodeSelector option for PodSpec

[aignatov]

No description provided.

[shamil]

@aignatov not sure this is needed, there is already Affinity in the spec that can do that

[aignatov]

@aignatov not sure this is needed, there is already Affinity in the spec that can do that

@shamil thanks for your reply. My use case is as follows:

• My redis pods has to be scheduled only to specific nodes with specific labels
• I also use anitiAffininty option not to collocate two pods with similar labels

Unfortunately I didn't find better way how to organize such deployment w/o nodeSelector option.

[shamil]

I've similar requirement, this is what I put in affinity block

affinity:
  nodeAffinity:
    requiredDuringSchedulingIgnoredDuringExecution:
      nodeSelectorTerms:
      - matchExpressions:
        - key: dedicated
          operator: In
          values: ['redis']
  podAntiAffinity:
    requiredDuringSchedulingIgnoredDuringExecution:
    - labelSelector:
        matchLabels:
          app.kubernetes.io/instance: tokens
          app.kubernetes.io/name: redis
      topologyKey: kubernetes.io/hostname

[aignatov]

@shamil you're right, it's possible to do so but I'm worried about performance of old k8s clusters with several hundreds of nodes. Here is a opened discussion about it:
kubernetes/kubernetes#72479

Also nodeSelector looks like straightforward option (just like clear node filtering by labels) for other cases which may not requiring complex affinity rules. I mean why not have this option if k8s allows it. :)

[toha10]

LGTM

[toha10]

@nrvnrvn or somebody with permissions on merge, please take a look

[nrvnrvn]

@aignatov thanks for the contribution
@toha10 thanks for the heads up ;)