fix: convert prometheus metrics to use gauge type (#640)

Author: titilambert

internal/metric/metric.go

@@ -18,19 +18,19 @@ func initRegistry() *Registry {
 
 	registry := &Registry{
 		reg: prometheus.NewRegistry(),
-		backupBytesProcessed: prometheus.NewSummaryVec(prometheus.SummaryOpts{
+		backupBytesProcessed: prometheus.NewGaugeVec(prometheus.GaugeOpts{
 			Name: "backrest_backup_bytes_processed",
 			Help: "The total number of bytes processed during a backup",
 		}, commonDims),
-		backupBytesAdded: prometheus.NewSummaryVec(prometheus.SummaryOpts{
+		backupBytesAdded: prometheus.NewGaugeVec(prometheus.GaugeOpts{
 			Name: "backrest_backup_bytes_added",
 			Help: "The total number of bytes added during a backup",
 		}, commonDims),
-		backupFileWarnings: prometheus.NewSummaryVec(prometheus.SummaryOpts{
+		backupFileWarnings: prometheus.NewGaugeVec(prometheus.GaugeOpts{
 			Name: "backrest_backup_file_warnings",
 			Help: "The total number of file warnings during a backup",
 		}, commonDims),
-		tasksDuration: prometheus.NewSummaryVec(prometheus.SummaryOpts{
+		tasksDuration: prometheus.NewGaugeVec(prometheus.GaugeOpts{
 			Name: "backrest_tasks_duration_secs",
 			Help: "The duration of a task in seconds",
 		}, append(slices.Clone(commonDims), "task_type")),
@@ -55,10 +55,10 @@ func GetRegistry() *Registry {
 
 type Registry struct {
 	reg                  *prometheus.Registry
-	backupBytesProcessed *prometheus.SummaryVec
-	backupBytesAdded     *prometheus.SummaryVec
-	backupFileWarnings   *prometheus.SummaryVec
-	tasksDuration        *prometheus.SummaryVec
+	backupBytesProcessed *prometheus.GaugeVec
+	backupBytesAdded     *prometheus.GaugeVec
+	backupFileWarnings   *prometheus.GaugeVec
+	tasksDuration        *prometheus.GaugeVec
 	tasksRun             *prometheus.CounterVec
 }
 
@@ -73,12 +73,13 @@ func (r *Registry) RecordTaskRun(repoID, planID, taskType string, duration_secs
 	if planID == "" {
 		planID = "_unassociated_"
 	}
+	r.tasksRun.DeletePartialMatch(prometheus.Labels{"repo_id": repoID, "plan_id": planID, "task_type": taskType})
 	r.tasksRun.WithLabelValues(repoID, planID, taskType, status).Inc()
-	r.tasksDuration.WithLabelValues(repoID, planID, taskType).Observe(duration_secs)
+	r.tasksDuration.WithLabelValues(repoID, planID, taskType).Set(duration_secs)
 }
 
 func (r *Registry) RecordBackupSummary(repoID, planID string, bytesProcessed, bytesAdded int64, fileWarnings int64) {
-	r.backupBytesProcessed.WithLabelValues(repoID, planID).Observe(float64(bytesProcessed))
-	r.backupBytesAdded.WithLabelValues(repoID, planID).Observe(float64(bytesAdded))
-	r.backupFileWarnings.WithLabelValues(repoID, planID).Observe(float64(fileWarnings))
+	r.backupBytesProcessed.WithLabelValues(repoID, planID).Set(float64(bytesProcessed))
+	r.backupBytesAdded.WithLabelValues(repoID, planID).Set(float64(bytesAdded))
+	r.backupFileWarnings.WithLabelValues(repoID, planID).Set(float64(fileWarnings))
 }