fix(systemstatsmonitor): key disk_percent_used by device_name only

disk_percent_used declared only device_name but recorded four labels
(device_name, fs_type, mount_option, state). With per-metric label
validation, Record now rejects the undeclared labels and the metric is
dropped from the export (caught by the metriconly e2e).

Record only device_name, preserving the schema NPD has exported since the
metric was introduced: the OpenCensus view aggregated by device_name and
dropped the other tags, so on the wire this metric has always had a single
label. It also maps to the Google-owned
compute.googleapis.com/guest/disk/percent_used descriptor, which can reject
writes carrying undeclared label keys. Add a regression test pinning the
schema.

Author: hakman

pkg/systemstatsmonitor/disk_collector.go

@@ -330,7 +330,13 @@ func (dc *diskCollector) collect() {
 			klog.Errorf("Failed to record used bytes for %s: %v", deviceName, err)
 		}
 		if dc.mPercentUsed != nil {
-			if err := dc.mPercentUsed.Record(map[string]string{deviceNameLabel: deviceName, fsTypeLabel: fstype, mountOptionLabel: opttypes, stateLabel: "used"}, float64(usageStat.UsedPercent)); err != nil {
+			// disk_percent_used is keyed only by device_name, matching the
+			// label schema NPD has exported since the metric was introduced
+			// (the OpenCensus view aggregated by device_name and dropped the
+			// other tags). This also keeps writes compatible with the
+			// Google-owned compute.googleapis.com/guest/disk/percent_used
+			// descriptor.
+			if err := dc.mPercentUsed.Record(map[string]string{deviceNameLabel: deviceName}, float64(usageStat.UsedPercent)); err != nil {
 				klog.Errorf("Failed to record used percent for %s: %v", deviceName, err)
 			}
 		}

pkg/systemstatsmonitor/disk_collector_test.go

@@ -19,10 +19,44 @@ package systemstatsmonitor
 import (
 	"testing"
 
+	sdkmetric "go.opentelemetry.io/otel/sdk/metric"
+
 	ssmtypes "k8s.io/node-problem-detector/pkg/systemstatsmonitor/types"
+	"k8s.io/node-problem-detector/pkg/util/metrics"
+	otelutil "k8s.io/node-problem-detector/pkg/util/otel"
 )
 
 func TestDiskCollector(t *testing.T) {
 	dc := NewDiskCollectorOrDie(&ssmtypes.DiskStatsConfig{})
 	dc.collect()
 }
+
+// TestDiskCollectorPercentUsedLabels pins the label schema of disk_percent_used
+// to device_name only. NPD has exported it that way since the metric was
+// introduced (the OpenCensus view aggregated by device_name), and it maps to the
+// Google-owned compute.googleapis.com/guest/disk/percent_used descriptor, which
+// can reject writes carrying undeclared label keys. Because Record now rejects
+// undeclared labels, widening the declared set is the only way collect() could
+// emit a wider schema — so the metric must accept device_name and reject more.
+func TestDiskCollectorPercentUsedLabels(t *testing.T) {
+	otelutil.ResetForTesting()
+	defer otelutil.ResetForTesting()
+	otelutil.AddMetricReader(sdkmetric.NewManualReader())
+	otelutil.InitializeMeterProvider()
+
+	dc := NewDiskCollectorOrDie(&ssmtypes.DiskStatsConfig{
+		MetricsConfigs: map[string]ssmtypes.MetricConfig{
+			string(metrics.DiskPercentUsedID): {DisplayName: string(metrics.DiskPercentUsedID)},
+		},
+	})
+
+	// collect() records disk_percent_used keyed only by device_name.
+	if err := dc.mPercentUsed.Record(map[string]string{deviceNameLabel: "sda1"}, 42.0); err != nil {
+		t.Fatalf("recording disk_percent_used with device_name failed: %v", err)
+	}
+
+	// A wider label set must be rejected, keeping the exported schema stable.
+	if err := dc.mPercentUsed.Record(map[string]string{deviceNameLabel: "sda1", fsTypeLabel: "ext4"}, 42.0); err == nil {
+		t.Error("disk_percent_used accepted an fs_type label; its schema must stay device_name-only")
+	}
+}