fix: honor -stderrthreshold when -logtostderr is set#850
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sudermanjr merged 2 commits intoFairwindsOps:masterfrom Apr 23, 2026
Merged
fix: honor -stderrthreshold when -logtostderr is set#850sudermanjr merged 2 commits intoFairwindsOps:masterfrom
sudermanjr merged 2 commits intoFairwindsOps:masterfrom
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klog v2 defaults -logtostderr to true, which silently causes -stderrthreshold to be ignored. klog v2.140.0 introduced the legacy_stderr_threshold_behavior flag that restores the correct interaction between the two flags (see kubernetes/klog#432). This commit sets legacy_stderr_threshold_behavior=false after klog.InitFlags in cmd/root.go and sets stderrthreshold=INFO so the default behavior is preserved but users can now override it on the command line. Ref: kubernetes/klog#212 Signed-off-by: Pierluigi Lenoci <pierluigi.lenoci@gmail.com> Signed-off-by: Pierluigi Lenoci <pierluigilenoci@gmail.com>
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What this PR does
klog v2 defaults
-logtostderrtotrue, which silently causes-stderrthresholdto be ignored — all log messages of every severity 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.
klog v2.140.0 (kubernetes/klog#432) introduces a
legacy_stderr_threshold_behaviorflag that fixes this. This PR setslegacy_stderr_threshold_behavior=falseafterklog.InitFlagsincmd/root.goand setsstderrthreshold=INFOso the default behavior is preserved but users can now override it on the command line (e.g.-stderrthreshold=WARNING).goldilocks is already on klog v2.140.0, so no dependency bump is needed.
Why it matters
In production clusters, log aggregation systems (Fluentd, Fluent Bit, Loki, Datadog, etc.) typically ingest logs from container stderr. When every log level goes to stderr indiscriminately:
The
-stderrthresholdflag exists precisely to solve this, but it has never worked under the default klog v2 configuration — until now.Changed files
cmd/root.golegacy_stderr_threshold_behavior=false+stderrthreshold=INFOafterklog.InitFlags