fix: honor --stderrthreshold flag when --logtostderr is enabled by pierluigilenoci · Pull Request #1485 · openshift/machine-api-operator

pierluigilenoci · 2026-03-28T21:46:59Z

What this PR does

When --logtostderr is enabled (which is the default in klog and explicitly set in all entry points), klog's legacy behavior silently ignores the --stderrthreshold flag. This means users cannot filter log output by severity level, even though the flag appears to be available.

This PR opts into the fixed behavior introduced in klog v2.140.0 by setting:

legacy_stderr_threshold_behavior=false — disables the legacy override
stderrthreshold=INFO — preserves the current default behavior

After this change, users can set --stderrthreshold=WARNING (or any level) and it will work as expected.

All entry points in cmd/ are updated:

cmd/machineset
cmd/nodelink-controller
cmd/vsphere
cmd/machine-api-operator (start + version subcommands)
cmd/machine-healthcheck

klog dependency updated from v2.130.1 to v2.140.0 (which introduces the legacy_stderr_threshold_behavior flag).

Why

See upstream fix: kubernetes/klog#432

Testing

Verified machine-api-operator builds successfully with updated dependency
Verified --stderrthreshold=WARNING now correctly filters output when --logtostderr is enabled

coderabbitai · 2026-03-28T21:47:14Z

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⛔ Files ignored due to path filters (10)

vendor/k8s.io/klog/v2/README.md is excluded by !vendor/**, !**/vendor/**
vendor/k8s.io/klog/v2/internal/serialize/keyvalues.go is excluded by !vendor/**, !**/vendor/**
vendor/k8s.io/klog/v2/internal/serialize/keyvalues_no_slog.go is excluded by !vendor/**, !**/vendor/**
vendor/k8s.io/klog/v2/internal/serialize/keyvalues_slog.go is excluded by !vendor/**, !**/vendor/**
vendor/k8s.io/klog/v2/klog.go is excluded by !vendor/**, !**/vendor/**
vendor/k8s.io/klog/v2/klogr.go is excluded by !vendor/**, !**/vendor/**
vendor/k8s.io/klog/v2/klogr_slog.go is excluded by !vendor/**, !**/vendor/**
vendor/k8s.io/klog/v2/textlogger/options.go is excluded by !vendor/**, !**/vendor/**
vendor/k8s.io/klog/v2/textlogger/textlogger.go is excluded by !vendor/**, !**/vendor/**
vendor/modules.txt is excluded by !vendor/**, !**/vendor/**

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Walkthrough

Added programmatic klog flag settings across multiple command entrypoints and bumped klog to v2.140.0: each entrypoint now sets logtostderr=true, disables legacy_stderr_threshold_behavior, and sets stderrthreshold=INFO (with failure handling).

Changes

Cohort / File(s)	Summary
klog Dependency Update `go.mod`	Bumped `k8s.io/klog/v2` from `v2.130.1` to `v2.140.0`.
Stderr threshold & klog flag config `cmd/machine-api-operator/start.go`, `cmd/machine-api-operator/version.go`, `cmd/machineset/main.go`, `cmd/nodelink-controller/main.go`, `cmd/vsphere/main.go`, `cmd/machine-healthcheck/main.go`	After enabling `logtostderr=true`, added `flag.Set` calls to set `legacy_stderr_threshold_behavior=false` and `stderrthreshold=INFO`; each call is checked and failure triggers `klog.Fatalf`.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Assessment against linked issues

Objective	Addressed	Explanation
Fix stderrthreshold being ignored when logtostderr=true [`#432`]	✅
Enable opt-in severity filtering via legacy_stderr_threshold_behavior flag [`#432`]	❌	Code force-sets `legacy_stderr_threshold_behavior=false` programmatically, which opts into the new behavior by default instead of leaving legacy behavior as the default opt-in state.
Set stderrthreshold to a specific level for filtering [`#432`]	✅

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openshift-ci · 2026-03-28T21:47:16Z

Hi @pierluigilenoci. Thanks for your PR.

I'm waiting for a openshift member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work.

Regular contributors should join the org to skip this step.

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pierluigilenoci · 2026-03-28T21:47:18Z

cc @JoelSpeed @damdo — This is a straightforward klog fix to honor the `--stderrthreshold` flag when `--logtostderr` is enabled. Part of a broader campaign to fix this across the Kubernetes ecosystem (see kubernetes/klog#432). Would appreciate a review when you get a chance!

openshift-ci · 2026-03-28T21:47:22Z

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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/machine-healthcheck/main.go`:
- Around line 81-89: After calling klog.InitFlags(nil) in main (klog.InitFlags),
set the logtostderr flag to "true" like the other entry points do so the stderr
threshold behavior is applied consistently; add a flag.Set("logtostderr",
"true") immediately after klog.InitFlags(nil) alongside the existing flag.Set
calls for "legacy_stderr_threshold_behavior" and "stderrthreshold" to ensure
klog writes logs to stderr as expected.

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📥 Commits

Reviewing files that changed from the base of the PR and between b8fd345 and e6831c9.

⛔ Files ignored due to path filters (11)

go.sum is excluded by !**/*.sum
vendor/k8s.io/klog/v2/README.md is excluded by !vendor/**, !**/vendor/**
vendor/k8s.io/klog/v2/internal/serialize/keyvalues.go is excluded by !vendor/**, !**/vendor/**
vendor/k8s.io/klog/v2/internal/serialize/keyvalues_no_slog.go is excluded by !vendor/**, !**/vendor/**
vendor/k8s.io/klog/v2/internal/serialize/keyvalues_slog.go is excluded by !vendor/**, !**/vendor/**
vendor/k8s.io/klog/v2/klog.go is excluded by !vendor/**, !**/vendor/**
vendor/k8s.io/klog/v2/klogr.go is excluded by !vendor/**, !**/vendor/**
vendor/k8s.io/klog/v2/klogr_slog.go is excluded by !vendor/**, !**/vendor/**
vendor/k8s.io/klog/v2/textlogger/options.go is excluded by !vendor/**, !**/vendor/**
vendor/k8s.io/klog/v2/textlogger/textlogger.go is excluded by !vendor/**, !**/vendor/**
vendor/modules.txt is excluded by !vendor/**, !**/vendor/**

📒 Files selected for processing (7)

cmd/machine-api-operator/start.go
cmd/machine-api-operator/version.go
cmd/machine-healthcheck/main.go
cmd/machineset/main.go
cmd/nodelink-controller/main.go
cmd/vsphere/main.go
go.mod

cmd/machine-healthcheck/main.go

All five entry points (vsphere, machineset, machine-api-operator start/version, nodelink-controller) set logtostderr=true, which causes klog's legacy behavior to silently ignore the stderrthreshold flag. This opts into the fixed behavior introduced in klog v2.130.0 by setting legacy_stderr_threshold_behavior=false in all entry points. See: kubernetes/klog#432 Signed-off-by: Pierluigi Lenoci <pierluigi.lenoci@gmail.com>

The machine-healthcheck binary was missing the logtostderr and stderrthreshold flag.Set calls that were added to all other binaries. Signed-off-by: Pierluigi Lenoci <pierluigi.lenoci@gmail.com>

JoelSpeed · 2026-03-31T09:50:52Z

/ok-to-test

openshift-ci · 2026-03-31T10:21:06Z

@pierluigilenoci: 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/verify-deps	`b66c2e6`	link	true	`/test verify-deps`
ci/prow/e2e-aws-ovn-upgrade	`b66c2e6`	link	true	`/test e2e-aws-ovn-upgrade`
ci/prow/e2e-aws-operator	`b66c2e6`	link	true	`/test e2e-aws-operator`
ci/prow/golint	`b66c2e6`	link	true	`/test golint`
ci/prow/e2e-metal-ipi-virtualmedia	`b66c2e6`	link	true	`/test e2e-metal-ipi-virtualmedia`
ci/prow/unit	`b66c2e6`	link	true	`/test unit`
ci/prow/e2e-aws-ovn	`b66c2e6`	link	true	`/test e2e-aws-ovn`
ci/prow/regression-clusterinfra-aws-ipi-mapi	`b66c2e6`	link	false	`/test regression-clusterinfra-aws-ipi-mapi`
ci/prow/verify-crds-sync	`b66c2e6`	link	true	`/test verify-crds-sync`
ci/prow/e2e-metal-ipi	`b66c2e6`	link	true	`/test e2e-metal-ipi`
ci/prow/okd-scos-images	`b66c2e6`	link	true	`/test okd-scos-images`

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JoelSpeed · 2026-03-31T10:25:20Z

@pierluigilenoci Vendor is inconsistent, please run go mod vendor and commit the diff as a separate commit

Signed-off-by: Pierluigi Lenoci <pierluigi.lenoci@gmail.com>

pierluigilenoci · 2026-03-31T12:10:29Z

@JoelSpeed Done — I've run go mod vendor and committed the diff as a separate commit (f83e339). The vendor directory should now be consistent. Thank you for the review!

JoelSpeed · 2026-03-31T12:18:53Z

Changes LGTM assuming the E2Es run through ok and we can still see the expected logs

openshift-ci bot added the needs-ok-to-test Indicates a PR that requires an org member to verify it is safe to test. label Mar 28, 2026

openshift-ci bot requested review from damdo and nrb March 28, 2026 21:47

coderabbitai bot reviewed Mar 28, 2026

View reviewed changes

cmd/machine-healthcheck/main.go Show resolved Hide resolved

pierluigilenoci force-pushed the fix/honor-stderrthreshold branch from e6831c9 to 994d225 Compare March 28, 2026 22:19

fix: add stderrthreshold flags to machine-healthcheck binary

b66c2e6

The machine-healthcheck binary was missing the logtostderr and stderrthreshold flag.Set calls that were added to all other binaries. Signed-off-by: Pierluigi Lenoci <pierluigi.lenoci@gmail.com>

openshift-ci bot added ok-to-test Indicates a non-member PR verified by an org member that is safe to test. and removed needs-ok-to-test Indicates a PR that requires an org member to verify it is safe to test. labels Mar 31, 2026

chore: run go mod vendor for klog/v2 bump

f83e339

Signed-off-by: Pierluigi Lenoci <pierluigi.lenoci@gmail.com>

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fix: honor --stderrthreshold flag when --logtostderr is enabled#1485

fix: honor --stderrthreshold flag when --logtostderr is enabled#1485
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pierluigilenoci commented Mar 28, 2026

What this PR does

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