Honor stderrthreshold when logtostderr is enabled by pierluigilenoci · Pull Request #2109 · GoogleContainerTools/config-sync

pierluigilenoci · 2026-03-26T23:16:28Z

Summary

After klog.InitFlags, opt into the fixed stderrthreshold behavior introduced in klog v2.140.0
Bump k8s.io/klog/v2 from v2.130.1 to v2.140.0
Applied to four non-test call sites:
- cmd/nomos/nomos.go (uses named fs flagset)
- cmd/junit-report/main.go
- pkg/util/log/setup.go
- pkg/resourcegroup/controllers/log/setup.go
Updated vendored dependencies

Motivation

When logtostderr is enabled (the default), klog historically suppressed the stderrthreshold flag, meaning that WARNING and ERROR messages could not be selectively filtered. klog v2.140.0 introduced new flags (legacy_stderr_threshold_behavior) to opt into the corrected behavior where stderrthreshold is properly honored.

Reference: kubernetes/klog#212

Test plan

Verify the application still logs to stderr as expected
Confirm stderrthreshold flag can be used to control which severity levels appear on stderr

After calling klog.InitFlags, opt into the fixed stderrthreshold behavior added in klog v2.140.0 so that severe-enough messages are still mirrored to stderr when logtostderr is set. Reference: kubernetes/klog#212 Signed-off-by: Pierluigi Lenoci <pierluigi.lenoci@gmail.com>

google-oss-prow · 2026-03-26T23:16:38Z

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google-cla · 2026-03-26T23:16:39Z

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google-oss-prow · 2026-03-26T23:16:39Z

Hi @pierluigilenoci. Thanks for your PR.

I'm waiting for a GoogleContainerTools 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 · 2026-03-26T23:16:59Z

cc @sdowell for review

gemini-code-assist

Code Review

This pull request updates the k8s.io/klog/v2 dependency to v2.140.0 and configures several entry points to opt into the new stderrthreshold behavior by disabling legacy_stderr_threshold_behavior. The vendored klog code includes significant refactoring of key-value serialization to handle deduplication and adds a new WithHeader option to the textlogger. Feedback across multiple files indicates that errors returned by flag.Set are being ignored, which could lead to silent configuration failures and is inconsistent with existing error handling in the codebase.

gemini-code-assist · 2026-03-26T23:17:42Z

cmd/junit-report/main.go

+	_ = flag.Set("legacy_stderr_threshold_behavior", "false")
+	_ = flag.Set("stderrthreshold", "INFO")


The error returned by flag.Set is being ignored. If setting these flags fails (for example, if the klog version is incorrect and the flags don't exist), the application will continue with incorrect logging behavior silently. This defeats the purpose of this change. The error should be handled, probably by logging and exiting, similar to how other errors are handled in this application.

if err := flag.Set("legacy_stderr_threshold_behavior", "false"); err != nil { klog.Fatalf("Failed to set flag %q: %v", "legacy_stderr_threshold_behavior", err) } if err := flag.Set("stderrthreshold", "INFO"); err != nil { klog.Fatalf("Failed to set flag %q: %v", "stderrthreshold", err) }

gemini-code-assist · 2026-03-26T23:17:42Z

cmd/nomos/nomos.go

+	_ = fs.Set("legacy_stderr_threshold_behavior", "false")
+	_ = fs.Set("stderrthreshold", "INFO")


The error returned by fs.Set is being ignored. If setting these flags fails, the application will silently fall back to the old logging behavior, which is undesirable. The error should be handled to ensure the logging is configured as expected. A fatal log on error would be appropriate here.

Suggested change

_ = fs.Set("legacy_stderr_threshold_behavior", "false")

_ = fs.Set("stderrthreshold", "INFO")

if err := fs.Set("legacy_stderr_threshold_behavior", "false"); err != nil {

klog.Fatalf("Failed to set flag %q: %v", "legacy_stderr_threshold_behavior", err)

}

if err := fs.Set("stderrthreshold", "INFO"); err != nil {

klog.Fatalf("Failed to set flag %q: %v", "stderrthreshold", err)

}

gemini-code-assist · 2026-03-26T23:17:42Z

pkg/resourcegroup/controllers/log/setup.go

+	_ = flag.Set("legacy_stderr_threshold_behavior", "false")
+	_ = flag.Set("stderrthreshold", "INFO")


The errors returned by flag.Set are being ignored. This is inconsistent with the error handling for flag.Set("v", "1") just a few lines below. To ensure logging is configured correctly and to maintain consistency, these errors should be handled.

if err := flag.Set("legacy_stderr_threshold_behavior", "false"); err != nil { klog.Fatalf("Failed to set flag %q: %v", "legacy_stderr_threshold_behavior", err) } if err := flag.Set("stderrthreshold", "INFO"); err != nil { klog.Fatalf("Failed to set flag %q: %v", "stderrthreshold", err) }

gemini-code-assist · 2026-03-26T23:17:42Z

pkg/util/log/setup.go

+	_ = flag.Set("legacy_stderr_threshold_behavior", "false")
+	_ = flag.Set("stderrthreshold", "INFO")


The errors returned by flag.Set are being ignored, which is inconsistent with the error handling for flag.Set("logtostderr", "true") that follows. To ensure robust initialization, these errors should be handled, for example by calling klog.Fatal(err).

Suggested change

_ = flag.Set("legacy_stderr_threshold_behavior", "false")

_ = flag.Set("stderrthreshold", "INFO")

if err := flag.Set("legacy_stderr_threshold_behavior", "false"); err != nil {

klog.Fatal(err)

}

if err := flag.Set("stderrthreshold", "INFO"); err != nil {

klog.Fatal(err)

}

pierluigilenoci · 2026-03-27T00:20:19Z

@googlebot I signed it.

Address review feedback by wrapping flag.Set() calls with proper error checking instead of silently discarding errors. Signed-off-by: Pierluigi Lenoci <pierluigi.lenoci@gmail.com>

pierluigilenoci · 2026-03-27T17:38:42Z

I've addressed the review feedback — all flag.Set() / fs.Set() calls are now wrapped with proper error handling instead of discarding errors with _ =. The updated code uses if err := ...; err != nil { klog.Fatalf(...) } pattern consistently across all 4 files.

Could an org member run /ok-to-test to trigger CI? Thank you!

Camila-B · 2026-03-27T19:58:45Z

/ok-to-test

google-oss-prow bot requested review from cowsking and tiffanny29631 March 26, 2026 23:16

google-oss-prow bot added needs-ok-to-test size/L labels Mar 26, 2026

gemini-code-assist bot reviewed Mar 26, 2026

View reviewed changes

fix: add error handling for flag.Set calls

f0d4d73

Address review feedback by wrapping flag.Set() calls with proper error checking instead of silently discarding errors. Signed-off-by: Pierluigi Lenoci <pierluigi.lenoci@gmail.com>

google-oss-prow bot added ok-to-test and removed needs-ok-to-test labels Mar 27, 2026

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Honor stderrthreshold when logtostderr is enabled#2109

Honor stderrthreshold when logtostderr is enabled#2109
pierluigilenoci wants to merge 2 commits intoGoogleContainerTools:mainfrom
pierluigilenoci:fix/honor-stderrthreshold

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		_ = flag.Set("legacy_stderr_threshold_behavior", "false")
		_ = flag.Set("stderrthreshold", "INFO")

		_ = fs.Set("legacy_stderr_threshold_behavior", "false")
		_ = fs.Set("stderrthreshold", "INFO")

-	_ = fs.Set("legacy_stderr_threshold_behavior", "false")
-	_ = fs.Set("stderrthreshold", "INFO")
+if err := fs.Set("legacy_stderr_threshold_behavior", "false"); err != nil {
+		klog.Fatalf("Failed to set flag %q: %v", "legacy_stderr_threshold_behavior", err)
+	}
+	if err := fs.Set("stderrthreshold", "INFO"); err != nil {
+		klog.Fatalf("Failed to set flag %q: %v", "stderrthreshold", err)
+	}

-	_ = flag.Set("legacy_stderr_threshold_behavior", "false")
-	_ = flag.Set("stderrthreshold", "INFO")
+if err := flag.Set("legacy_stderr_threshold_behavior", "false"); err != nil {
+		klog.Fatal(err)
+	}
+	if err := flag.Set("stderrthreshold", "INFO"); err != nil {
+		klog.Fatal(err)
+	}

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pierluigilenoci commented Mar 26, 2026

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