Add support for preferredDuringSchedulingIgnoredDuringExecution #73

Copilot · 2026-01-13T17:14:45Z

Adds soft node affinity constraints to complement the existing hard requiredDuringSchedulingIgnoredDuringExecution support. This enables prioritizing spot/preemptible nodes while falling back to regular nodes when unavailable.

Changes

Core implementation:

Extended NamespaceConfig with PreferredNodeSelectorTerms field (uses preferredNodeSelectorTerms in config for consistency with nodeSelectorTerms)
Added patch building logic (buildPreferredAffinityPath, buildPreferredAffinityPatch, buildPreferredAffinityInitPatch)
Updated buildPatch() to handle preferred affinity alongside required affinity
Modified config validation to accept at least one of: nodeSelectorTerms, preferredNodeSelectorTerms, or tolerations

Documentation:

Updated README with preferred affinity semantics (weights 1-100, soft scheduling)
Added example ConfigMap entries for preferred-only and combined required+preferred scenarios

Naming convention:

Field named preferredNodeSelectorTerms for consistency with existing nodeSelectorTerms field, maintaining backwards compatibility

Example Usage

Prefer spot nodes but allow fallback to any node:

testing-ns-preferred: |
  preferredNodeSelectorTerms:
    - weight: 100
      preference:
        matchExpressions:
        - key: spot
          operator: In
          values:
          - "true"

Require dedicated nodes, prefer spot subset:

testing-ns-combined: |
  nodeSelectorTerms:
    - matchExpressions:
      - key: dedicated
        operator: In
        values:
        - "true"
  preferredNodeSelectorTerms:
    - weight: 100
      preference:
        matchExpressions:
        - key: spot
          operator: In
          values:
          - "true"

The implementation follows the same JSON patch approach as existing required affinity support, ensuring consistency and compatibility.

Original prompt

This section details on the original issue you should resolve

<issue_title>Add support for preferredDuringSchedulingIgnoredDuringExecution</issue_title>
<issue_description>Hey, putting in a request for this to be added as it would be nice to have. The use case I am looking at is specifically around spot node pools in Azure/AKS. I would like to be able to prioritize using the spot node pools, but fall back on regular/dedicated nodes if the spot node pools get evicted.</issue_description>

<agent_instructions>Add support for configuring preferredDuringSchedulingIgnoredDuringExecution alongside with the currently available requiredDuringSchedulingIgnoredDuringExecution. Documentation is available here: https://kubernetes.io/docs/concepts/scheduling-eviction/assign-pod-node/</agent_instructions>

Comments on the Issue (you are @copilot in this section)
@idgenchev Hi @tadeha, didn't have much time to support the project recently but I'm planning to add this feature next month and the new release will come immediately after.

Fixes Add support for preferredDuringSchedulingIgnoredDuringExecution #40

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Co-authored-by: idgenchev <1568180+idgenchev@users.noreply.github.com>

idgenchev · 2026-01-15T13:56:16Z

README.md

 It is a replacement for the [PodNodeSelector](https://kubernetes.io/docs/reference/access-authn-authz/admission-controllers/#podnodeselector) admission controller and it is useful when using a managed k8s control plane such as [GKE](https://cloud.google.com/kubernetes-engine) or [EKS](https://aws.amazon.com/eks) where you do not have the ability to enable additional admission controller plugins and the [PodNodeSelector](https://kubernetes.io/docs/reference/access-authn-authz/admission-controllers/#podnodeselector) might not be available. The only admission controller plugin required to run the namespace-node-affinity mutating webhook is the `MutatingAdmissionWebhook` which is already enabled on most managed Kubernetes services such as [EKS](https://docs.aws.amazon.com/eks/latest/userguide/platform-versions.html).

-It might still be useful on [AKS](https://azure.microsoft.com/en-gb/services/kubernetes-service/) where the [PodNodeSelector](https://kubernetes.io/docs/reference/access-authn-authz/admission-controllers/#podnodeselector) admission controller is [readily available](https://docs.microsoft.com/en-us/azure/aks/faq#what-kubernetes-admission-controllers-does-aks-support-can-admission-controllers-be-added-or-removed) as using `namespace-node-affinity` allows a litte bit more flexibility than the node selector by allowing you to set node affinity (only `requiredDuringSchedulingIgnoredDuringExecution` is supported for now) for all pods in the namespace.
+It might still be useful on [AKS](https://azure.microsoft.com/en-gb/services/kubernetes-service/) where the [PodNodeSelector](https://kubernetes.io/docs/reference/access-authn-authz/admission-controllers/#podnodeselector) admission controller is [readily available](https://docs.microsoft.com/en-us/azure/aks/faq#what-kubernetes-admission-controllers-does-aks-support-can-admission-controllers-be-added-or-removed) as using `namespace-node-affinity` allows a litte bit more flexibility than the node selector by allowing you to set node affinity (both `requiredDuringSchedulingIgnoredDuringExecution` and `preferredDuringSchedulingIgnoredDuringExecution` are supported) for all pods in the namespace.


No need to specify that requiredDuringSchedulingIgnoredDuringExecution and preferredDuringSchedulingIgnoredDuringExecution are supported anymore as these are the only two options.

Updated to remove the specific mention of the two types in commit 40b3f35.

idgenchev · 2026-01-15T14:00:41Z

examples/sample_configmap.yaml

        operator: "Exists"
        effect: "NoSchedule"
+  testing-ns-preferred: |
+    preferredDuringSchedulingIgnoredDuringExecution:


Naming here becomes inconsistent and confusing. Something like preferredNodeSelectorTerms will work better as we already have nodeSelectorTerms and I'd like to keep that as is for backwards compatibility.

Renamed from preferredDuringSchedulingIgnoredDuringExecution to preferredNodeSelectorTerms in commit 40b3f35 for naming consistency.

idgenchev · 2026-01-15T14:08:42Z

injector/injector.go

+	AddPreferredDuringScheduling   = "/spec/affinity/nodeAffinity/preferredDuringSchedulingIgnoredDuringExecution"
+	AddToPreferredDuringScheduling = "/spec/affinity/nodeAffinity/preferredDuringSchedulingIgnoredDuringExecution/-"


Same here, with the naming. Maybe something like AddPreferredNodeSelectorTerms will work better here.

Renamed constants to AddPreferredNodeSelectorTerms and AddToPreferredNodeSelectorTerms in commit 40b3f35.

idgenchev · 2026-01-15T14:09:24Z

injector/injector.go

-	Tolerations       []corev1.Toleration       `json:"tolerations"`
-	ExcludedLabels    map[string]string         `json:"excludedLabels"`
+	NodeSelectorTerms                               []corev1.NodeSelectorTerm        `json:"nodeSelectorTerms"`
+	PreferredDuringSchedulingIgnoredDuringExecution []corev1.PreferredSchedulingTerm `json:"preferredDuringSchedulingIgnoredDuringExecution"`


Here as well - PreferredNodeSelectorTerms will work better if the NodeSelectorTerms filed is kept as is for backwards compatibility.

Updated struct field to PreferredNodeSelectorTerms in commit 40b3f35 to maintain consistency with NodeSelectorTerms.

Co-authored-by: idgenchev <1568180+idgenchev@users.noreply.github.com>

codecov-commenter · 2026-01-15T14:22:36Z

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Codecov Report

❌ Patch coverage is 91.93548% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 84.65%. Comparing base (cfcfe8e) to head (40b3f35).

Files with missing lines	Patch %	Lines
injector/injector.go	91.93%	4 Missing and 1 partial ⚠️
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@@            Coverage Diff             @@
##             main      #73      +/-   ##
==========================================
+ Coverage   83.27%   84.65%   +1.37%     
==========================================
  Files           3        3              
  Lines         305      365      +60     
==========================================
+ Hits          254      309      +55     
- Misses         48       52       +4     
- Partials        3        4       +1

Flag	Coverage Δ
unittests	`84.65% <91.93%> (+1.37%)`	⬆️

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Initial plan

35b3549

Copilot AI assigned Copilot and idgenchev Jan 13, 2026

Copilot started work on behalf of idgenchev January 13, 2026 17:15 View session

Copilot AI and others added 2 commits January 13, 2026 17:22

Add support for preferredDuringSchedulingIgnoredDuringExecution

ba9a37f

Co-authored-by: idgenchev <1568180+idgenchev@users.noreply.github.com>

Remove unused constant preferredAffinityKey

3c7c8dd

Co-authored-by: idgenchev <1568180+idgenchev@users.noreply.github.com>

Copilot AI changed the title ~~[WIP] Add support for preferredDuringSchedulingIgnoredDuringExecution~~ Add support for preferredDuringSchedulingIgnoredDuringExecution Jan 13, 2026

Copilot AI requested a review from idgenchev January 13, 2026 17:27

Copilot finished work on behalf of idgenchev January 13, 2026 17:27

idgenchev requested changes Jan 15, 2026

View reviewed changes

Copilot started work on behalf of idgenchev January 15, 2026 14:10 View session

Rename to preferredNodeSelectorTerms for consistency

40b3f35

Co-authored-by: idgenchev <1568180+idgenchev@users.noreply.github.com>

idgenchev marked this pull request as ready for review January 15, 2026 14:30

Copilot AI requested a review from idgenchev January 15, 2026 14:30

Copilot finished work on behalf of idgenchev January 15, 2026 14:30

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		AddPreferredDuringScheduling = "/spec/affinity/nodeAffinity/preferredDuringSchedulingIgnoredDuringExecution"
		AddToPreferredDuringScheduling = "/spec/affinity/nodeAffinity/preferredDuringSchedulingIgnoredDuringExecution/-"

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