snapshot of https://github.com/ory/keto.git (master, 2026-09-16; blobs > 131072B omitted)

oryx/prometheusx/exemplar.go

@@ -0,0 +1,61 @@
+// Copyright © 2026 Ory Corp
+// SPDX-License-Identifier: Apache-2.0
+
+package prometheusx
+
+import (
+	"context"
+
+	"github.com/prometheus/client_golang/prometheus"
+	"go.opentelemetry.io/otel/trace"
+)
+
+// ExemplarFromContext returns exemplar labels (trace_id, span_id) for the
+// sampled trace span in ctx, or nil when there is none. The nil return makes
+// it directly usable with promhttp.WithExemplarFromContext.
+func ExemplarFromContext(ctx context.Context) prometheus.Labels {
+	sc := trace.SpanContextFromContext(ctx)
+	if !sc.IsValid() || !sc.IsSampled() {
+		return nil
+	}
+	return prometheus.Labels{
+		"trace_id": sc.TraceID().String(),
+		"span_id":  sc.SpanID().String(),
+	}
+}
+
+// AddWithExemplar adds v to counter. When ctx carries a sampled trace span,
+// the addition carries a trace exemplar so dashboards can link the counter
+// to the trace. Any panic from exemplar validation is swallowed: a lost
+// exemplar must never break the recording path, and client_golang applies
+// the addition before validating the exemplar, so the count is recorded
+// either way.
+func AddWithExemplar(ctx context.Context, counter prometheus.Counter, v float64) {
+	exemplar := ExemplarFromContext(ctx)
+	adder, ok := counter.(prometheus.ExemplarAdder)
+	if exemplar == nil || !ok {
+		counter.Add(v)
+		return
+	}
+	defer func() {
+		_ = recover()
+	}()
+	adder.AddWithExemplar(v, exemplar)
+}
+
+// ObserveWithExemplar records v on obs. When ctx carries a sampled trace
+// span, the observation carries a trace exemplar on the histogram bucket it
+// falls into. The same panic-swallowing rationale as AddWithExemplar
+// applies.
+func ObserveWithExemplar(ctx context.Context, obs prometheus.Observer, v float64) {
+	exemplar := ExemplarFromContext(ctx)
+	observer, ok := obs.(prometheus.ExemplarObserver)
+	if exemplar == nil || !ok {
+		obs.Observe(v)
+		return
+	}
+	defer func() {
+		_ = recover()
+	}()
+	observer.ObserveWithExemplar(v, exemplar)
+}