feat(chart): add PodDisruptionBudget for high availability

[vishnukothakapu]

Description

This adds an optional PodDisruptionBudget to the Helm chart (charts/node-readiness-controller). Since the controller manages node taints, it's critical infrastructure. Adding a PDB allows users running multiple replicas to ensure the controller remains highly available during node drains, cluster upgrades, or other evictions.

The PDB is disabled by default (podDisruptionBudget.enabled: false). Existing installations that do not explicitly opt-in to this feature will see no changes in rendered manifests.

Related Issue

Fixes #410

Type of Change

/kind feature

Testing

• Added helm-unittest coverage in charts/node-readiness-controller/tests/pdb_test.yaml to ensure it only renders when enabled, respects minAvailable / maxUnavailable, and correctly inherits the selector labels.

Checklist

• make test passes
• make lint passes

Does this PR introduce a user-facing change?

Helm chart: Added `podDisruptionBudget` configuration options for high availability during node drains and evictions.

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[kubernetes-prow]

Hi @vishnukothakapu. Thanks for your PR.

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[Ayush4958]

It's seems good to me
@ajaysundark can review for further review

[vitorfloriano]

/test pull-node-readiness-controller-junit-report-canary

[AvineshTripathi]

/ok-to-test

[ajaysundark]

same as #437 (comment). I want to better understand what level of preconfiguration will be handled at the helm chart. Could you help us with some research? Thanks!

[ajaysundark]

@Ayush4958 had some references at #437.

It's good to add to our charts. Thanks @vishnukothakapu .

/lgtm

[ajaysundark]

the helm tests are failing and need your second look

/assign @vishnukothakapu

[ajaysundark]

/ok-to-test

[ajaysundark]

/lgtm
/approve

[kubernetes-prow]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: ajaysundark, Ayush4958, vishnukothakapu

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