OCPBUGS-78154: Use HA leader election defaults for MCO on SNO

[lucaconsalvi]

- What I did

In SNO clusters, after a non-graceful node reboot the Machine Config Controller (MCC) takes ~5-6 minutes to acquire its leader lease. This is because GetLeaderElectionConfig() applies library-go's SNO leader election timings (LeaseDuration=270s, RetryPeriod=60s, worst non-graceful acquisition=330s).

Since MCO runs exactly one replica on SNO, there is zero lease contention — the inflated SNO timings provide no benefit and only add recovery latency.

This PR adds a GetDefaultLeaderElectionConfig() function that returns HA defaults (LeaseDuration=137s, RetryPeriod=26s, worst non-graceful acquisition=163s) regardless of topology. Only MCC uses it; MCO and MOB retain the existing topology-aware configuration.

Fixes: https://issues.redhat.com/browse/OCPBUGS-78154

- How to verify it

1. Deploy a SNO cluster (tested on OCP 4.20.15 and 4.22.0-ec.3)
2. Reboot the node: ssh core@<node> 'sudo systemctl reboot --force'
3. After reboot, check MCC logs: oc logs -n openshift-machine-config-operator -l k8s-app=machine-config-controller
4. Verify the log line: "SNO topology detected, using HA leader election defaults"
5. Check lease values: oc get lease -n openshift-machine-config-operator machine-config-controller -o yaml - leaseDurationSeconds should be 137 (was 270)
6. Measure lease acquisition time — expected ~2m30s (was ~5m30s)

- Description for the changelog
Use HA leader election defaults for MCO on SNO to reduce post-reboot lease acquisition delay from ~5.5min to ~2.5min

Summary by CodeRabbit

• Refactor
  • Enhanced high availability configuration handling with standardized default leader election timings independent of cluster topology.

[openshift-ci]

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[openshift-ci-robot]

@lucaconsalvi: This pull request references Jira Issue OCPBUGS-78154, which is invalid:

• expected the bug to target the "4.22.0" version, but no target version was set

Comment /jira refresh to re-evaluate validity if changes to the Jira bug are made, or edit the title of this pull request to link to a different bug.

The bug has been updated to refer to the pull request using the external bug tracker.

Details

In response to this:

- What I did

In SNO clusters, after a non-graceful node reboot the Machine Config Controller (MCC) takes ~5-6 minutes to acquire its leader lease. This is because GetLeaderElectionConfig() applies library-go's SNO leader election timings (LeaseDuration=270s, RetryPeriod=60s, worst non-graceful acquisition=330s).

Since MCO runs exactly one replica on SNO, there is zero lease contention — the inflated SNO timings provide no benefit and only add recovery latency.

This PR removes the LeaderElectionSNOConfig() override so MCO uses HA defaults (LeaseDuration=137s, RetryPeriod=26s, worst non-graceful acquisition=163s) on all topologies.

Fixes: https://issues.redhat.com/browse/OCPBUGS-78154

- How to verify it

1. Deploy a SNO cluster (tested on OCP 4.20.15 and 4.22.0-ec.3)
2. Reboot the node: ssh core@<node> 'sudo systemctl reboot --force'
3. After reboot, check MCC logs: oc logs -n openshift-machine-config-operator -l k8s-app=machine-config-controller
4. Verify the log line: "SNO topology detected, using HA leader election defaults"
5. Check lease values: oc get lease -n openshift-machine-config-operator machine-config-controller -o yaml - leaseDurationSeconds should be 137 (was 270)
6. Measure lease acquisition time — expected ~2m30s (was ~5m30s)

- Description for the changelog
Use HA leader election defaults for MCO on SNO to reduce post-reboot lease acquisition delay from ~5.5min to ~2.5min

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[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Repository: openshift/coderabbit/.coderabbit.yaml

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Run ID: 958ee88d-46b7-4933-bf9f-78de9fb6e379

📥 Commits

Reviewing files that changed from the base of the PR and between 65d648b and 34cd2aa.

📒 Files selected for processing (2)

• cmd/common/helpers.go
• cmd/machine-config-controller/start.go

🚧 Files skipped from review as they are similar to previous changes (1)

• cmd/common/helpers.go

---

Walkthrough

Adds a new function GetDefaultLeaderElectionConfig() that returns default HA leader election timings independent of cluster topology. Updates machine-config-controller to use this new function instead of the topology-aware variant.

Changes

Cohort / File(s)	Summary
Leader Election Configuration cmd/common/helpers.go, cmd/machine-config-controller/start.go	Added GetDefaultLeaderElectionConfig() function that initializes and returns default leader election timings with logging. Updated start.go to call this new function instead of GetLeaderElectionConfig() for configuration retrieval.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~8 minutes

🚥 Pre-merge checks | ✅ 7 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 50.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (7 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title directly references the Jira ticket (OCPBUGS-78154) and clearly describes the main change: using HA leader election defaults for the Machine Config Controller on Single Node OpenShift clusters to reduce acquisition latency.
Stable And Deterministic Test Names	✅ Passed	PR modifies only non-test files (helpers.go and start.go). No Ginkgo test files are added or modified.
Test Structure And Quality	✅ Passed	No Ginkgo test files were modified in this PR, only implementation files. The custom check for test code quality is not applicable.
Microshift Test Compatibility	✅ Passed	This PR does not introduce any new Ginkgo e2e tests. Modifications are limited to two source files adding a helper function and updating the start command. No e2e tests with Ginkgo patterns are added.
Single Node Openshift (Sno) Test Compatibility	✅ Passed	PR does not add new Ginkgo e2e tests; changes only affect production code in cmd/common/helpers.go and cmd/machine-config-controller/start.go, making this check not applicable.
Ipv6 And Disconnected Network Test Compatibility	✅ Passed	This PR does not add Ginkgo e2e tests; changes are limited to implementation files modifying leader election configuration logic.

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Error: can't load config: unsupported version of the configuration: "" See https://golangci-lint.run/docs/product/migration-guide for migration instructions
The command is terminated due to an error: can't load config: unsupported version of the configuration: "" See https://golangci-lint.run/docs/product/migration-guide for migration instructions

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[openshift-ci]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: lucaconsalvi
Once this PR has been reviewed and has the lgtm label, please assign yuqi-zhang for approval. For more information see the Code Review Process.

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Inline comments:
In `@cmd/common/helpers.go`:
- Around line 72-74: When useDefaultTimings is true the code returns
defaultLeaderElection silently; add an informational log just before that return
to record that HA default timings are being forced regardless of topology (e.g.,
log.Printf or the project's logger: log.Infof/klog.Infof) and include the value
being returned (defaultLeaderElection) and the flag name useDefaultTimings so
operators can see this decision in logs; update imports if necessary and place
the log immediately above the return in the same function where
useDefaultTimings and defaultLeaderElection are referenced.

---

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Configuration used: Repository: openshift/coderabbit/.coderabbit.yaml

Review profile: CHILL

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Run ID: 204a9bcc-63b8-4156-a8c7-8d82e3e88901

📥 Commits

Reviewing files that changed from the base of the PR and between f016a8e and 165da5a.

📒 Files selected for processing (4)

• cmd/common/helpers.go
• cmd/machine-config-controller/start.go
• cmd/machine-config-operator/start.go
• cmd/machine-os-builder/start.go

[openshift-ci]

@lucaconsalvi: The following tests failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
ci/prow/e2e-gcp-op-part2	34cd2aa	link	true	/test e2e-gcp-op-part2
ci/prow/e2e-aws-ovn-upgrade	34cd2aa	link	true	/test e2e-aws-ovn-upgrade

Full PR test history. Your PR dashboard.

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