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

When logtostderr is enabled, klog's legacy behavior ignores the
stderrthreshold flag. This opts into the fixed behavior introduced in
klog v2.130.0 by setting legacy_stderr_threshold_behavior=false.

See: kubernetes/klog#432
Signed-off-by: Pierluigi Lenoci <pierluigi.lenoci@gmail.com>

Author: pierluigilenoci

go.mod

@@ -26,7 +26,7 @@ require (
 	k8s.io/api v0.32.10
 	k8s.io/apimachinery v0.32.10
 	k8s.io/client-go v0.32.10
-	k8s.io/klog/v2 v2.130.1
+	k8s.io/klog/v2 v2.140.0
 )
 
 require (

go.sum

@@ -432,8 +432,8 @@ k8s.io/apimachinery v0.32.10 h1:SAg2kUPLYRcBJQj66oniP1BnXSqw+l1GvJFsJlBmVvQ=
 k8s.io/apimachinery v0.32.10/go.mod h1:GpHVgxoKlTxClKcteaeuF1Ul/lDVb74KpZcxcmLDElE=
 k8s.io/client-go v0.32.10 h1:MFmIjsKtcnn7mStjrJG1ZW2WzLsKKn6ZtL9hHM/W0xU=
 k8s.io/client-go v0.32.10/go.mod h1:qJy/Ws3zSwnu/nD75D+/of1uxbwWHxrYT5P3FuobVLI=
-k8s.io/klog/v2 v2.130.1 h1:n9Xl7H1Xvksem4KFG4PYbdQCQxqc/tTUyrgXaOhHSzk=
-k8s.io/klog/v2 v2.130.1/go.mod h1:3Jpz1GvMt720eyJH1ckRHK1EDfpxISzJ7I9OYgaDtPE=
+k8s.io/klog/v2 v2.140.0 h1:Tf+J3AH7xnUzZyVVXhTgGhEKnFqye14aadWv7bzXdzc=
+k8s.io/klog/v2 v2.140.0/go.mod h1:o+/RWfJ6PwpnFn7OyAG3QnO47BFsymfEfrz6XyYSSp0=
 k8s.io/kube-openapi v0.0.0-20241105132330-32ad38e42d3f h1:GA7//TjRY9yWGy1poLzYYJJ4JRdzg3+O6e8I+e+8T5Y=
 k8s.io/kube-openapi v0.0.0-20241105132330-32ad38e42d3f/go.mod h1:R/HEjbvWI0qdfb8viZUeVZm0X6IZnxAydC7YU42CMw4=
 k8s.io/utils v0.0.0-20241104100929-3ea5e8cea738 h1:M3sRQVHv7vB20Xc2ybTt7ODCeFj6JSWYFzOFnYeS6Ro=

main.go

@@ -147,6 +147,17 @@ func init() {
 		os.Exit(1)
 	}
 
+	// Opt into the fixed klog behavior so the --stderrthreshold flag is honored
+	// even when --logtostderr is enabled. See https://github.com/kubernetes/klog/issues/432
+	if err := flag.Set("legacy_stderr_threshold_behavior", "false"); err != nil {
+		log.Error("Can't set the legacy_stderr_threshold_behavior flag", err)
+		os.Exit(1)
+	}
+	if err := flag.Set("stderrthreshold", "INFO"); err != nil {
+		log.Error("Can't set the stderrthreshold flag", err)
+		os.Exit(1)
+	}
+
 	// Only copy the non file logging options from klog
 	copyFlag("v")
 	copyFlag("vmodule")