Merge branch 'main' into sparsehistogram

Author: beorn7

examples/gocollector/main.go

@@ -22,6 +22,7 @@ import (
 	"fmt"
 	"log"
 	"net/http"
+	"regexp"
 
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/client_golang/prometheus/collectors"
@@ -39,7 +40,7 @@ func main() {
 	// Add Go module build info.
 	reg.MustRegister(collectors.NewBuildInfoCollector())
 	reg.MustRegister(collectors.NewGoCollector(
-		collectors.WithGoCollections(collectors.GoRuntimeMemStatsCollection | collectors.GoRuntimeMetricsCollection),
+		collectors.WithGoCollectorRuntimeMetrics(collectors.GoRuntimeMetricsRule{Matcher: regexp.MustCompile("/.*")}),
 	))
 
 	// Expose the registered metrics via HTTP.

prometheus/counter.go

@@ -140,12 +140,13 @@ func (c *counter) get() float64 {
 }
 
 func (c *counter) Write(out *dto.Metric) error {
-	val := c.get()
-
+	// Read the Exemplar first and the value second. This is to avoid a race condition
+	// where users see an exemplar for a not-yet-existing observation.
 	var exemplar *dto.Exemplar
 	if e := c.exemplar.Load(); e != nil {
 		exemplar = e.(*dto.Exemplar)
 	}
+	val := c.get()
 
 	return populateMetric(CounterValue, val, c.labelPairs, exemplar, out)
 }

prometheus/histogram.go

@@ -1170,7 +1170,7 @@ func (h *constHistogram) Write(out *dto.Metric) error {
 // to send it to Prometheus in the Collect method.
 //
 // buckets is a map of upper bounds to cumulative counts, excluding the +Inf
-// bucket.
+// bucket. The +Inf bucket is implicit, and its value is equal to the provided count.
 //
 // NewConstHistogram returns an error if the length of labelValues is not
 // consistent with the variable labels in Desc or if Desc is invalid.

prometheus/metric.go

@@ -187,7 +187,7 @@ func (m *withExemplarsMetric) Write(pb *dto.Metric) error {
 			} else {
 				// The +Inf bucket should be explicitly added if there is an exemplar for it, similar to non-const histogram logic in https://github.com/prometheus/client_golang/blob/main/prometheus/histogram.go#L357-L365.
 				b := &dto.Bucket{
-					CumulativeCount: proto.Uint64(pb.Histogram.Bucket[len(pb.Histogram.GetBucket())-1].GetCumulativeCount()),
+					CumulativeCount: proto.Uint64(pb.Histogram.GetSampleCount()),
 					UpperBound:      proto.Float64(math.Inf(1)),
 					Exemplar:        e,
 				}

prometheus/metric_test.go

@@ -79,10 +79,14 @@ func TestWithExemplarsMetric(t *testing.T) {
 			}
 		}
 
-		infBucket := metric.GetHistogram().Bucket[len(metric.GetHistogram().Bucket)-1].GetUpperBound()
+		infBucket := metric.GetHistogram().Bucket[len(metric.GetHistogram().Bucket)-1]
 
-		if infBucket != math.Inf(1) {
-			t.Errorf("want %v, got %v", math.Inf(1), infBucket)
+		if want, got := math.Inf(1), infBucket.GetUpperBound(); want != got {
+			t.Errorf("want %v, got %v", want, got)
+		}
+
+		if want, got := uint64(4711), infBucket.GetCumulativeCount(); want != got {
+			t.Errorf("want %v, got %v", want, got)
 		}
 	})
 }

prometheus/promauto/auto.go

@@ -14,13 +14,13 @@
 // Package promauto provides alternative constructors for the fundamental
 // Prometheus metric types and their …Vec and …Func variants. The difference to
 // their counterparts in the prometheus package is that the promauto
-// constructors return Collectors that are already registered with a
-// registry. There are two sets of constructors. The constructors in the first
-// set are top-level functions, while the constructors in the other set are
-// methods of the Factory type. The top-level function return Collectors
-// registered with the global registry (prometheus.DefaultRegisterer), while the
-// methods return Collectors registered with the registry the Factory was
-// constructed with. All constructors panic if the registration fails.
+// constructors register the Collectors with a registry before returning them.
+// There are two sets of constructors. The constructors in the first set are
+// top-level functions, while the constructors in the other set are methods of
+// the Factory type. The top-level function return Collectors registered with
+// the global registry (prometheus.DefaultRegisterer), while the methods return
+// Collectors registered with the registry the Factory was constructed with. All
+// constructors panic if the registration fails.
 //
 // The following example is a complete program to create a histogram of normally
 // distributed random numbers from the math/rand package: