feat(metrics): Add traceID exemplar to scrape duration histogram (#121)

Signed-off-by: Dave Henderson <[email protected]>
hairyhenderson · Dec 23, 2024 · 9dff72a · 9dff72a
1 parent 6b553c1
commit 9dff72a
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Showing 2 changed files with 13 additions and 4 deletions.
diff --git a/cmd/sagemcom_fast_exporter/exporter_metrics.go b/cmd/sagemcom_fast_exporter/exporter_metrics.go
@@ -1,9 +1,11 @@
 package main
 
 import (
+	"context"
 	"time"
 
 	"github.com/prometheus/client_golang/prometheus"
+	"go.opentelemetry.io/otel/trace"
 )
 
 type scrapeObserver struct {
@@ -40,8 +42,15 @@ func newScrapeObserver() *scrapeObserver {
 	}
 }
 
-func (o *scrapeObserver) Observe(duration time.Duration, success bool) {
-	o.scrapeDuration.Observe(duration.Seconds())
+func (o *scrapeObserver) Observe(ctx context.Context, duration time.Duration, success bool) {
+	// add traceID as exemplar, if available
+	traceID := trace.SpanFromContext(ctx).SpanContext().TraceID()
+	if traceID.IsValid() {
+		o.scrapeDuration.(prometheus.ExemplarObserver).ObserveWithExemplar(duration.Seconds(),
+			prometheus.Labels{"traceID": traceID.String()})
+	} else {
+		o.scrapeDuration.Observe(duration.Seconds())
+	}
 
 	if success {
 		o.scrapeSuccess.Set(1)

diff --git a/collector/collector.go b/collector/collector.go
@@ -513,7 +513,7 @@ func initWiFiSSIDMetrics(ns string) wifiSSIDMetrics {
 }
 
 type ScrapeObserver interface {
-	Observe(duration time.Duration, success bool)
+	Observe(ctx context.Context, duration time.Duration, success bool)
 }
 
 func New(ctx context.Context, scraper client.Scraper, scrapeObserver ScrapeObserver) prometheus.Collector {
@@ -550,7 +550,7 @@ func (c *collector) Collect(ch chan<- prometheus.Metric) {
 		slog.Default().ErrorContext(ctx, "update error", "err", err)
 	}
 
-	c.scrapeObserver.Observe(time.Since(start), err == nil)
+	c.scrapeObserver.Observe(ctx, time.Since(start), err == nil)
 }
 
 func (c *collector) update(ctx context.Context, ch chan<- prometheus.Metric) error {