[deco] use DeleteLabelValues properly with a caching solution to remo…

…ve defunct metrics

cmd/file-exporter/files.go

@@ -43,7 +43,6 @@ func readFiles() error {
 			return nil
 		}
 
-		fmt.Printf("visited file or dir: %q\n", path)
 		err = processFile(path)
 		if err != nil {
 			return err

cmd/file-exporter/main.go

@@ -12,7 +12,7 @@ import (
 
 func Version(c *gin.Context) {
 	rs := map[string]any{
-		"version": "v0.0.8",
+		"version": "v0.0.9",
 	}
 	c.AbortWithStatusJSON(200, rs)
 }
@@ -32,7 +32,9 @@ func livenessHandler() http.HandlerFunc {
 func Metrics() http.HandlerFunc {
 	return func(writer http.ResponseWriter, request *http.Request) {
 		for key := range global_labels {
-			global_labels[key] = false
+			tmp := global_labels[key]
+			tmp.Valid = false
+			global_labels[key] = tmp
 		}
 
 		err := readFiles()
@@ -43,9 +45,12 @@ func Metrics() http.HandlerFunc {
 		}
 
 		for key, val := range global_labels {
-			log.Println(key, val)
-			if !val {
-				global_metrics[key].Reset()
+			if !val.Valid {
+				ok := global_metrics[key].DeleteLabelValues(val.Labels...)
+				if ok {
+					delete(global_metrics, key)
+					delete(global_labels, key)
+				}
 			}
 		}
 

cmd/file-exporter/metrics.go

@@ -1,14 +1,20 @@
 package main
 
 import (
+	"errors"
 	"strings"
 
 	"github.com/DictumMortuum/servus-extapi/pkg/util"
 	"github.com/prometheus/client_golang/prometheus"
 )
 
+type CachedLabels struct {
+	Labels []string
+	Valid  bool
+}
+
 var (
-	global_labels  = map[string]bool{}
+	global_labels  = map[string]CachedLabels{}
 	global_metrics = map[string]*prometheus.MetricVec{}
 )
 
@@ -36,10 +42,19 @@ func toMetric(raw string) error {
 	)
 
 	val := util.Atof(raw_val)
-	prometheus.Unregister(metric)
-	prometheus.MustRegister(metric)
-	global_labels[key_name+"_"+key_namespace] = true
-	global_metrics[key_name+"_"+key_namespace] = metric.MetricVec
+	are := &prometheus.AlreadyRegisteredError{}
+	err := prometheus.Register(metric)
+	if errors.As(err, are) {
+		metric = are.ExistingCollector.(*prometheus.GaugeVec)
+	} else if err != nil {
+		return err
+	}
+	// prometheus.MustRegister(metric)
+	global_labels[s[0]] = CachedLabels{
+		Valid:  true,
+		Labels: vals,
+	}
+	global_metrics[s[0]] = metric.MetricVec
 	metric.WithLabelValues(vals...).Set(val)
 
 	return nil