Use actual lease duration from Kubernetes object in leader election

[Copilot]

LeaderElector.TryAcquireOrRenew was using the locally configured lease duration instead of the value from the Kubernetes object, breaking graceful step-downs where leaders signal their departure by setting lease duration to 1 second.

Changes

• Use oldLeaderElectionRecord.LeaseDurationSeconds from the Kubernetes object instead of config.LeaseDuration when checking lease expiration
• Add unit test LeaderElectionUsesActualLeaseDurationFromKubernetesObject to verify the fix

// Before: ignores actual lease duration from K8s
if (!string.IsNullOrEmpty(oldLeaderElectionRecord.HolderIdentity)
    && observedTime + config.LeaseDuration > DateTimeOffset.Now
    && !IsLeader())

// After: respects actual lease duration from K8s object
if (!string.IsNullOrEmpty(oldLeaderElectionRecord.HolderIdentity)
    && observedTime + TimeSpan.FromSeconds(oldLeaderElectionRecord.LeaseDurationSeconds) > DateTimeOffset.Now
    && !IsLeader())

This aligns the C# implementation with the Go client-go behavior.

Testing

• ✅ All 7 leader election tests pass
• ✅ New test validates that actual lease duration (1 second for graceful step-down) is respected instead of configured duration (10 seconds)

Original prompt

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This section details on the original issue you should resolve

<issue_title>Actual lease duration is ignored in LeaderElector.TryAcquireOrRenew</issue_title>
<issue_description>Describe the bug
LeaderElector.TryAcquireOrRenew uses the lease duration from the local configuration, instead of the Kubernetes object, assuming that the two values are the same.

This might not be true during graceful step downs, as libraries like the one for Golang set the lease duration to 1 second as a way to signal the leader has stepped down. C# clients would ignore this and still wait for the entire pre-configured duration of the lease before trying to acquire the lease.

This behaviour also differs from the Golang library, which uses the lease duration from the actual Kubernetes object.

Kubernetes C# SDK Client Version
14.0.2

Server Kubernetes Version
1.30.13

Dotnet Runtime Version
net8

To Reproduce
Create a lease and change its duration to 1s

Expected behavior
Non-leader C# clients should try to take the lease

Where do you run your app with Kubernetes SDK (please complete the following information):

• OS: Linux
• Environment: Container
• Cloud: AWS and on-prem
  </issue_description>

<agent_instructions>fix this</agent_instructions>

Comments on the Issue (you are @copilot in this section)

@tg123 agreed, there is some gap between the golang and .net and those should be filled, let me take a look @k8s-ci-robot @k8s-triage-robot: Closing this issue, marking it as "Not Planned".

Details

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/close not-planned

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• Fixes Actual lease duration is ignored in LeaderElector.TryAcquireOrRenew #1640

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[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: Copilot
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[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: Copilot
Once this PR has been reviewed and has the lgtm label, please ask for approval from tg123. For more information see the Code Review Process.

The full list of commands accepted by this bot can be found here.

Details

Needs approval from an approver in each of these files:

• OWNERS

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[tg123]

@copilot could you please add ut

[Copilot]

@copilot could you please add ut

Added unit test in commit 826586f. The test LeaderElectionUsesActualLeaseDurationFromKubernetesObject validates that the actual lease duration from the Kubernetes object (1 second for graceful step-down) is respected instead of the configured duration (10 seconds). All 7 leader election tests pass.

[Copilot]

Pull request overview

This PR fixes a bug where the leader election mechanism was using the locally configured lease duration instead of the actual lease duration from the Kubernetes object. This prevented proper handling of graceful leader step-downs, where outgoing leaders signal their departure by setting the lease duration to 1 second. The fix aligns the C# implementation with the Go client-go behavior.

Key changes:

• Modified lease expiration check to use the actual LeaseDurationSeconds value from the Kubernetes object instead of the configured duration
• Added comprehensive unit test to validate that graceful step-downs with 1-second lease durations work correctly

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
src/KubernetesClient/LeaderElection/LeaderElector.cs	Updated TryAcquireOrRenew method to use oldLeaderElectionRecord.LeaseDurationSeconds instead of config.LeaseDuration when checking if a lease has expired
tests/KubernetesClient.Tests/LeaderElection/LeaderElectionTests.cs	Added test LeaderElectionUsesActualLeaseDurationFromKubernetesObject that validates the fix by ensuring a 1-second lease duration from the Kubernetes object is respected instead of a 10-second configured duration

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