Remove unnecessary check if label is nil in observeWithExemplar (#1235)

* Remove unnecessary check if label is nil in observeWithExemplar instrumentation

Signed-off-by: dlituyev <[email protected]>

* Remove unnecessary check if label is nil in observeWithExemplar instrumentation

Signed-off-by: dlituyev <[email protected]>

---------

Signed-off-by: dlituyev <[email protected]>
Co-authored-by: dlituyev <[email protected]>

Author: dimonl

prometheus/promhttp/instrument_client.go

@@ -78,7 +78,7 @@ func InstrumentRoundTripperCounter(counter *prometheus.CounterVec, next http.Rou
 			for label, resolve := range rtOpts.extraLabelsFromCtx {
 				l[label] = resolve(resp.Request.Context())
 			}
-			addWithExemplar(counter.With(l), 1, rtOpts.getExemplarFn(r.Context()))
+			counter.With(l).(prometheus.ExemplarAdder).AddWithExemplar(1, rtOpts.getExemplarFn(r.Context()))
 		}
 		return resp, err
 	}
@@ -122,7 +122,7 @@ func InstrumentRoundTripperDuration(obs prometheus.ObserverVec, next http.RoundT
 			for label, resolve := range rtOpts.extraLabelsFromCtx {
 				l[label] = resolve(resp.Request.Context())
 			}
-			observeWithExemplar(obs.With(l), time.Since(start).Seconds(), rtOpts.getExemplarFn(r.Context()))
+			obs.With(l).(prometheus.ExemplarObserver).ObserveWithExemplar(time.Since(start).Seconds(), rtOpts.getExemplarFn(r.Context()))
 		}
 		return resp, err
 	}

prometheus/promhttp/instrument_server.go

@@ -28,26 +28,6 @@ import (
 // magicString is used for the hacky label test in checkLabels. Remove once fixed.
 const magicString = "zZgWfBxLqvG8kc8IMv3POi2Bb0tZI3vAnBx+gBaFi9FyPzB/CzKUer1yufDa"
 
-// 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)
-}
-
-// 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
-	}
-	obs.(prometheus.ExemplarAdder).AddWithExemplar(val, labels)
-}
-
 // InstrumentHandlerInFlight is a middleware that wraps the provided
 // http.Handler. It sets the provided prometheus.Gauge to the number of
 // requests currently handled by the wrapped http.Handler.
@@ -100,7 +80,7 @@ func InstrumentHandlerDuration(obs prometheus.ObserverVec, next http.Handler, op
 			for label, resolve := range hOpts.extraLabelsFromCtx {
 				l[label] = resolve(r.Context())
 			}
-			observeWithExemplar(obs.With(l), time.Since(now).Seconds(), hOpts.getExemplarFn(r.Context()))
+			obs.With(l).(prometheus.ExemplarObserver).ObserveWithExemplar(time.Since(now).Seconds(), hOpts.getExemplarFn(r.Context()))
 		}
 	}
 
@@ -111,7 +91,7 @@ func InstrumentHandlerDuration(obs prometheus.ObserverVec, next http.Handler, op
 		for label, resolve := range hOpts.extraLabelsFromCtx {
 			l[label] = resolve(r.Context())
 		}
-		observeWithExemplar(obs.With(l), time.Since(now).Seconds(), hOpts.getExemplarFn(r.Context()))
+		obs.With(l).(prometheus.ExemplarObserver).ObserveWithExemplar(time.Since(now).Seconds(), hOpts.getExemplarFn(r.Context()))
 	}
 }
 
@@ -150,7 +130,7 @@ func InstrumentHandlerCounter(counter *prometheus.CounterVec, next http.Handler,
 			for label, resolve := range hOpts.extraLabelsFromCtx {
 				l[label] = resolve(r.Context())
 			}
-			addWithExemplar(counter.With(l), 1, hOpts.getExemplarFn(r.Context()))
+			counter.With(l).(prometheus.ExemplarAdder).AddWithExemplar(1, hOpts.getExemplarFn(r.Context()))
 		}
 	}
 
@@ -161,7 +141,7 @@ func InstrumentHandlerCounter(counter *prometheus.CounterVec, next http.Handler,
 		for label, resolve := range hOpts.extraLabelsFromCtx {
 			l[label] = resolve(r.Context())
 		}
-		addWithExemplar(counter.With(l), 1, hOpts.getExemplarFn(r.Context()))
+		counter.With(l).(prometheus.ExemplarAdder).AddWithExemplar(1, hOpts.getExemplarFn(r.Context()))
 	}
 }
 
@@ -203,7 +183,7 @@ func InstrumentHandlerTimeToWriteHeader(obs prometheus.ObserverVec, next http.Ha
 			for label, resolve := range hOpts.extraLabelsFromCtx {
 				l[label] = resolve(r.Context())
 			}
-			observeWithExemplar(obs.With(l), time.Since(now).Seconds(), hOpts.getExemplarFn(r.Context()))
+			obs.With(l).(prometheus.ExemplarObserver).ObserveWithExemplar(time.Since(now).Seconds(), hOpts.getExemplarFn(r.Context()))
 		})
 		next.ServeHTTP(d, r)
 	}
@@ -247,7 +227,7 @@ func InstrumentHandlerRequestSize(obs prometheus.ObserverVec, next http.Handler,
 			for label, resolve := range hOpts.extraLabelsFromCtx {
 				l[label] = resolve(r.Context())
 			}
-			observeWithExemplar(obs.With(l), float64(size), hOpts.getExemplarFn(r.Context()))
+			obs.With(l).(prometheus.ExemplarObserver).ObserveWithExemplar(float64(size), hOpts.getExemplarFn(r.Context()))
 		}
 	}
 
@@ -259,7 +239,7 @@ func InstrumentHandlerRequestSize(obs prometheus.ObserverVec, next http.Handler,
 		for label, resolve := range hOpts.extraLabelsFromCtx {
 			l[label] = resolve(r.Context())
 		}
-		observeWithExemplar(obs.With(l), float64(size), hOpts.getExemplarFn(r.Context()))
+		obs.With(l).(prometheus.ExemplarObserver).ObserveWithExemplar(float64(size), hOpts.getExemplarFn(r.Context()))
 	}
 }
 
@@ -299,7 +279,7 @@ func InstrumentHandlerResponseSize(obs prometheus.ObserverVec, next http.Handler
 		for label, resolve := range hOpts.extraLabelsFromCtx {
 			l[label] = resolve(r.Context())
 		}
-		observeWithExemplar(obs.With(l), float64(d.Written()), hOpts.getExemplarFn(r.Context()))
+		obs.With(l).(prometheus.ExemplarObserver).ObserveWithExemplar(float64(d.Written()), hOpts.getExemplarFn(r.Context()))
 	})
 }