Fix prometheus histogram and summary merging (#6756)

plugins/serializers/prometheus/collection.go

@@ -52,12 +52,32 @@ type Histogram struct {
 	Sum     float64
 }
 
+func (h *Histogram) merge(b Bucket) {
+	for i := range h.Buckets {
+		if h.Buckets[i].Bound == b.Bound {
+			h.Buckets[i].Count = b.Count
+			return
+		}
+	}
+	h.Buckets = append(h.Buckets, b)
+}
+
 type Summary struct {
 	Quantiles []Quantile
 	Count     uint64
 	Sum       float64
 }
 
+func (s *Summary) merge(q Quantile) {
+	for i := range s.Quantiles {
+		if s.Quantiles[i].Quantile == q.Quantile {
+			s.Quantiles[i].Value = q.Value
+			return
+		}
+	}
+	s.Quantiles = append(s.Quantiles, q)
+}
+
 type MetricKey uint64
 
 func MakeMetricKey(labels []LabelPair) MetricKey {
@@ -210,7 +230,6 @@ func (c *Collection) Add(metric telegraf.Metric) {
 				Scaler: &Scaler{Value: value},
 			}
 
-			// what if already here
 			entry.Metrics[metricKey] = m
 		case telegraf.Histogram:
 			if m == nil {
@@ -236,7 +255,7 @@ func (c *Collection) Add(metric telegraf.Metric) {
 					continue
 				}
 
-				m.Histogram.Buckets = append(m.Histogram.Buckets, Bucket{
+				m.Histogram.merge(Bucket{
 					Bound: bound,
 					Count: count,
 				})
@@ -297,7 +316,7 @@ func (c *Collection) Add(metric telegraf.Metric) {
 					continue
 				}
 
-				m.Summary.Quantiles = append(m.Summary.Quantiles, Quantile{
+				m.Summary.merge(Quantile{
 					Quantile: quantile,
 					Value:    value,
 				})