Clarify exemplar(Add|Observe) by renaming to (add|observe)WithExemplar (#1122)

* Clarify exemplarAdd by renaming to addWithExemplar

Signed-off-by: Dave Henderson <[email protected]>

* Documenting addWithExemplar

Signed-off-by: Dave Henderson <[email protected]>

* Also rename exemplarObserve to follow the same pattern

Signed-off-by: Dave Henderson <[email protected]>

Signed-off-by: Dave Henderson <[email protected]>

Author: hairyhenderson

prometheus/promhttp/instrument_client.go

@@ -73,7 +73,7 @@ func InstrumentRoundTripperCounter(counter *prometheus.CounterVec, next http.Rou
 	return func(r *http.Request) (*http.Response, error) {
 		resp, err := next.RoundTrip(r)
 		if err == nil {
-			exemplarAdd(
+			addWithExemplar(
 				counter.With(labels(code, method, r.Method, resp.StatusCode, rtOpts.extraMethods...)),
 				1,
 				rtOpts.getExemplarFn(r.Context()),
@@ -116,7 +116,7 @@ func InstrumentRoundTripperDuration(obs prometheus.ObserverVec, next http.RoundT
 		start := time.Now()
 		resp, err := next.RoundTrip(r)
 		if err == nil {
-			exemplarObserve(
+			observeWithExemplar(
 				obs.With(labels(code, method, r.Method, resp.StatusCode, rtOpts.extraMethods...)),
 				time.Since(start).Seconds(),
 				rtOpts.getExemplarFn(r.Context()),

prometheus/promhttp/instrument_server.go

@@ -28,15 +28,19 @@ import (
 // magicString is used for the hacky label test in checkLabels. Remove once fixed.
 const magicString = "zZgWfBxLqvG8kc8IMv3POi2Bb0tZI3vAnBx+gBaFi9FyPzB/CzKUer1yufDa"
 
-func exemplarObserve(obs prometheus.Observer, val float64, labels map[string]string) {
+// observeWithExemplar is a wrapper for [prometheus.ExemplarAdder.ExemplarObserver],
+// which falls back to [prometheus.Observer.Observe] if no labels are provided.
+func observeWithExemplar(obs prometheus.Observer, val float64, labels map[string]string) {
 	if labels == nil {
 		obs.Observe(val)
 		return
 	}
 	obs.(prometheus.ExemplarObserver).ObserveWithExemplar(val, labels)
 }
 
-func exemplarAdd(obs prometheus.Counter, val float64, labels map[string]string) {
+// addWithExemplar is a wrapper for [prometheus.ExemplarAdder.AddWithExemplar],
+// which falls back to [prometheus.Counter.Add] if no labels are provided.
+func addWithExemplar(obs prometheus.Counter, val float64, labels map[string]string) {
 	if labels == nil {
 		obs.Add(val)
 		return
@@ -91,7 +95,7 @@ func InstrumentHandlerDuration(obs prometheus.ObserverVec, next http.Handler, op
 			d := newDelegator(w, nil)
 			next.ServeHTTP(d, r)
 
-			exemplarObserve(
+			observeWithExemplar(
 				obs.With(labels(code, method, r.Method, d.Status(), hOpts.extraMethods...)),
 				time.Since(now).Seconds(),
 				hOpts.getExemplarFn(r.Context()),
@@ -103,7 +107,7 @@ func InstrumentHandlerDuration(obs prometheus.ObserverVec, next http.Handler, op
 		now := time.Now()
 		next.ServeHTTP(w, r)
 
-		exemplarObserve(
+		observeWithExemplar(
 			obs.With(labels(code, method, r.Method, 0, hOpts.extraMethods...)),
 			time.Since(now).Seconds(),
 			hOpts.getExemplarFn(r.Context()),
@@ -141,7 +145,7 @@ func InstrumentHandlerCounter(counter *prometheus.CounterVec, next http.Handler,
 			d := newDelegator(w, nil)
 			next.ServeHTTP(d, r)
 
-			exemplarAdd(
+			addWithExemplar(
 				counter.With(labels(code, method, r.Method, d.Status(), hOpts.extraMethods...)),
 				1,
 				hOpts.getExemplarFn(r.Context()),
@@ -151,7 +155,7 @@ func InstrumentHandlerCounter(counter *prometheus.CounterVec, next http.Handler,
 
 	return func(w http.ResponseWriter, r *http.Request) {
 		next.ServeHTTP(w, r)
-		exemplarAdd(
+		addWithExemplar(
 			counter.With(labels(code, method, r.Method, 0, hOpts.extraMethods...)),
 			1,
 			hOpts.getExemplarFn(r.Context()),
@@ -192,7 +196,7 @@ func InstrumentHandlerTimeToWriteHeader(obs prometheus.ObserverVec, next http.Ha
 	return func(w http.ResponseWriter, r *http.Request) {
 		now := time.Now()
 		d := newDelegator(w, func(status int) {
-			exemplarObserve(
+			observeWithExemplar(
 				obs.With(labels(code, method, r.Method, status, hOpts.extraMethods...)),
 				time.Since(now).Seconds(),
 				hOpts.getExemplarFn(r.Context()),
@@ -233,7 +237,7 @@ func InstrumentHandlerRequestSize(obs prometheus.ObserverVec, next http.Handler,
 			d := newDelegator(w, nil)
 			next.ServeHTTP(d, r)
 			size := computeApproximateRequestSize(r)
-			exemplarObserve(
+			observeWithExemplar(
 				obs.With(labels(code, method, r.Method, d.Status(), hOpts.extraMethods...)),
 				float64(size),
 				hOpts.getExemplarFn(r.Context()),
@@ -244,7 +248,7 @@ func InstrumentHandlerRequestSize(obs prometheus.ObserverVec, next http.Handler,
 	return func(w http.ResponseWriter, r *http.Request) {
 		next.ServeHTTP(w, r)
 		size := computeApproximateRequestSize(r)
-		exemplarObserve(
+		observeWithExemplar(
 			obs.With(labels(code, method, r.Method, 0, hOpts.extraMethods...)),
 			float64(size),
 			hOpts.getExemplarFn(r.Context()),
@@ -282,7 +286,7 @@ func InstrumentHandlerResponseSize(obs prometheus.ObserverVec, next http.Handler
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		d := newDelegator(w, nil)
 		next.ServeHTTP(d, r)
-		exemplarObserve(
+		observeWithExemplar(
 			obs.With(labels(code, method, r.Method, d.Status(), hOpts.extraMethods...)),
 			float64(d.Written()),
 			hOpts.getExemplarFn(r.Context()),