Use an atomic label write

Signed-off-by: Tuomas Katila <[email protected]>

Author: tkatila

cmd/internal/labeler/labeler.go

@@ -379,6 +379,26 @@ func createNumaNodeMappingLabel(mapping map[int][]string) string {
 	return strings.Join(parts, "_")
 }
 
+func (l *labeler) atomicPrintLabelsToFile(labelFile string) error {
+	baseDir := filepath.Dir(labelFile)
+
+	d, err := os.MkdirTemp(baseDir, "labels")
+	if err != nil {
+		klog.Warning("could not create temporary directory, writing directly to destination")
+
+		return l.printLabelsToFile(labelFile)
+	}
+	defer os.RemoveAll(d)
+
+	tmpFile := filepath.Join(d, "labels.txt")
+
+	if err := l.printLabelsToFile(tmpFile); err != nil {
+		return err
+	}
+
+	return os.Rename(tmpFile, labelFile)
+}
+
 func (l *labeler) printLabelsToFile(labelFile string) error {
 	f, err := os.OpenFile(labelFile, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)
 	if err != nil {
@@ -448,7 +468,7 @@ func Run(sysfsDrmDir, nfdFeatureFile string, updateInterval time.Duration, scanR
 		if l.labelsChanged {
 			klog.V(1).Info("Writing labels")
 
-			if err := l.printLabelsToFile(nfdFeatureFile); err != nil {
+			if err := l.atomicPrintLabelsToFile(nfdFeatureFile); err != nil {
 				klog.Warningf("failed to write labels to file: %+v", err)
 
 				// Reset labels so that next time the labeler runs the writing is retried.