Remove -Inf buckets from go collector histograms (#1049)

* Remove -Inf buckets from go collector histograms

Signed-off-by: Kemal Akkoyun <kakkoyun@gmail.com>

* Update prometheus/collectors/go_collector_latest_test.go

Co-authored-by: Bartlomiej Plotka <bwplotka@gmail.com>
Signed-off-by: Kemal Akkoyun <kakkoyun@gmail.com>

* Simplify

Signed-off-by: Kemal Akkoyun <kakkoyun@gmail.com>

Co-authored-by: Bartlomiej Plotka <bwplotka@gmail.com>

prometheus/collectors/go_collector_latest_test.go

@@ -0,0 +1,39 @@
+// Copyright 2021 The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//go:build go1.17
+// +build go1.17
+
+package collectors
+
+import (
+	"encoding/json"
+	"testing"
+
+	"github.com/prometheus/client_golang/prometheus"
+)
+
+func TestGoCollectorMarshalling(t *testing.T) {
+	reg := prometheus.NewRegistry()
+	reg.MustRegister(NewGoCollector(
+		WithGoCollections(GoRuntimeMemStatsCollection | GoRuntimeMetricsCollection),
+	))
+	result, err := reg.Gather()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if _, err := json.Marshal(result); err != nil {
+		t.Errorf("json marshalling shoud not fail, %v", err)
+	}
+}

prometheus/go_collector_latest.go

@@ -25,8 +25,9 @@ import (
 
 	//nolint:staticcheck // Ignore SA1019. Need to keep deprecated package for compatibility.
 	"github.com/golang/protobuf/proto"
-	"github.com/prometheus/client_golang/prometheus/internal"
 	dto "github.com/prometheus/client_model/go"
+
+	"github.com/prometheus/client_golang/prometheus/internal"
 )
 
 const (
@@ -429,6 +430,11 @@ type batchHistogram struct {
 // buckets must always be from the runtime/metrics package, following
 // the same conventions.
 func newBatchHistogram(desc *Desc, buckets []float64, hasSum bool) *batchHistogram {
+	// We need to remove -Inf values. runtime/metrics keeps them around.
+	// But -Inf bucket should not be allowed for prometheus histograms.
+	if buckets[0] == math.Inf(-1) {
+		buckets = buckets[1:]
+	}
 	h := &batchHistogram{
 		desc:    desc,
 		buckets: buckets,
@@ -487,9 +493,11 @@ func (h *batchHistogram) Write(out *dto.Metric) error {
 	for i, count := range h.counts {
 		totalCount += count
 		if !h.hasSum {
+			if count != 0 {
 				// N.B. This computed sum is an underestimate.
 				sum += h.buckets[i] * float64(count)
 			}
+		}
 
 		// Skip the +Inf bucket, but only for the bucket list.
 		// It must still count for sum and totalCount.

prometheus/go_collector_metrics_go117_test.go

@@ -38,4 +38,4 @@ var expectedRuntimeMetrics = map[string]string{
 	"/sched/latencies:seconds":                    "go_sched_latencies_seconds",
 }
 
-const expectedRuntimeMetricsCardinality = 79
+const expectedRuntimeMetricsCardinality = 77

prometheus/go_collector_metrics_go118_test.go

@@ -38,4 +38,4 @@ var expectedRuntimeMetrics = map[string]string{
 	"/sched/latencies:seconds":                    "go_sched_latencies_seconds",
 }
 
-const expectedRuntimeMetricsCardinality = 79
+const expectedRuntimeMetricsCardinality = 77