Add system CPU metrics to metrics-v3 (#19560)

endpoint: /minio/metrics/v3/system/cpu

metrics:
- minio_system_cpu_avg_idle
- minio_system_cpu_avg_iowait
- minio_system_cpu_load
- minio_system_cpu_load_perc
- minio_system_cpu_nice
- minio_system_cpu_steal
- minio_system_cpu_system
- minio_system_cpu_user

cmd/metrics-resource.go

@@ -162,14 +162,7 @@ func init() {
 	resourceCollector = newMinioResourceCollector(resourceMetricsGroups)
 }
 
-func updateResourceMetrics(subSys MetricSubsystem, name MetricName, val float64, labels map[string]string, isCumulative bool) {
-	resourceMetricsMapMu.Lock()
-	defer resourceMetricsMapMu.Unlock()
-	subsysMetrics, found := resourceMetricsMap[subSys]
-	if !found {
-		subsysMetrics = ResourceMetrics{}
-	}
-
+func getResourceKey(name MetricName, labels map[string]string) string {
 	// labels are used to uniquely identify a metric
 	// e.g. reads_per_sec_{drive} inside the map
 	sfx := ""
@@ -180,7 +173,18 @@ func updateResourceMetrics(subSys MetricSubsystem, name MetricName, val float64,
 		sfx += v
 	}
 
-	key := string(name) + "_" + sfx
+	return string(name) + "_" + sfx
+}
+
+func updateResourceMetrics(subSys MetricSubsystem, name MetricName, val float64, labels map[string]string, isCumulative bool) {
+	resourceMetricsMapMu.Lock()
+	defer resourceMetricsMapMu.Unlock()
+	subsysMetrics, found := resourceMetricsMap[subSys]
+	if !found {
+		subsysMetrics = ResourceMetrics{}
+	}
+
+	key := getResourceKey(name, labels)
 	metric, found := subsysMetrics[key]
 	if !found {
 		metric = ResourceMetric{