Honor stderrthreshold when logtostderr is enabled

[pierluigilenoci]

What this PR does

Fixes the -stderrthreshold flag so it is honored even when -logtostderr=true (the klog v2 default).

Problem

klog v2 defaults -logtostderr to true. When this flag is active, the -stderrthreshold flag is silently ignored — all log messages (INFO, WARNING, ERROR, FATAL) are unconditionally written to stderr. There is no way for users to filter which severity levels reach stderr.

This has been an open issue since 2020: kubernetes/klog#212.

Fix

PR kubernetes/klog#432 introduced the fix in klog v2.140.0 via a new flag legacy_stderr_threshold_behavior. This PR:

1. Bumps klog from v2.130.1 to v2.140.0
2. Opts into the fixed behavior by setting legacy_stderr_threshold_behavior=false and stderrthreshold=INFO after every klog.InitFlags() call

Setting stderrthreshold=INFO preserves the current default behavior (all logs go to stderr). Users can now override it on the command line (e.g., -stderrthreshold=WARNING) and it will actually work.

Changes

• cmd/cadvisor.go: Main binary entry point
• client/clientexample/main.go: Client example
• utils/oomparser/oomexample/main.go: OOM parser example
• integration/runner/runner.go: Integration test runner
• integration/tests/api/test_utils.go: API test utilities
• integration/tests/crio/test_utils.go: CRI-O test utilities
• integration/tests/healthz/test_utils.go: Healthz test utilities
• go.mod / go.sum: Bump k8s.io/klog/v2 v2.130.1 → v2.140.0

Ref: kubernetes/klog#212, kubernetes/klog#432

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[pierluigilenoci]

Hi @vmarmol, @dashpole, @rjnagal -- would you be willing to review? Thank you!

[pierluigilenoci]

@googlebot I signed it.

[pierluigilenoci]

@googlebot I signed it.

[pierluigilenoci]

Hi @vmarmol @dashpole @rjnagal — friendly follow-up. The CLA check is passing. This is a small change to opt into the fixed klog stderrthreshold behavior.

Would you be able to review when you get a chance? Thank you!

[dashpole]

I don't work on cAdvisor anymore.

[pierluigilenoci]

Thank you for letting me know, @dashpole! Could @vmarmol or @rjnagal point me to the right person to review this? I see @thaJeztah and @olyazavr have been active recently — would either of you be able to take a look? It's a small klog stderrthreshold fix. Thank you!

[pierluigilenoci]

Hi @dims — friendly ping on this PR. It fixes the klog stderrthreshold behavior when logtostderr is enabled. Happy to address any feedback. Thanks!

[pierluigilenoci]

Hi @dims — gentle reminder on this PR. It fixes the klog stderrthreshold behavior when logtostderr is enabled (same fix as adopted in other k8s ecosystem projects). Happy to address any feedback. Thanks!

[pierluigilenoci]

Hi — friendly follow-up. CI is green and all checks pass. Would you be able to review when you get a chance? Thank you!