feat: ProtobufParse.formatOpenMetricsFloat: improve float formatting by using strconv.AppendFloat instead of fmt.Sprint

Signed-off-by: machine424 <ayoubmrini424@gmail.com>

model/textparse/protobufparse.go

@@ -20,7 +20,9 @@ import (
 	"fmt"
 	"io"
 	"math"
+	"strconv"
 	"strings"
+	"sync"
 	"unicode/utf8"
 
 	"github.com/gogo/protobuf/proto"
@@ -34,6 +36,15 @@ import (
 	dto "github.com/prometheus/prometheus/prompb/io/prometheus/client"
 )
 
+// floatFormatBufPool is exclusively used in formatOpenMetricsFloat.
+var floatFormatBufPool = sync.Pool{
+	New: func() interface{} {
+		// To contain at most 17 digits and additional syntax for a float64.
+		b := make([]byte, 0, 24)
+		return &b
+	},
+}
+
 // ProtobufParser is a very inefficient way of unmarshaling the old Prometheus
 // protobuf format and then present it as it if were parsed by a
 // Prometheus-2-style text parser. This is only done so that we can easily plug
@@ -629,11 +640,15 @@ func formatOpenMetricsFloat(f float64) string {
 	case math.IsInf(f, -1):
 		return "-Inf"
 	}
-	s := fmt.Sprint(f)
+	bp := floatFormatBufPool.Get().(*[]byte)
-	if strings.ContainsAny(s, "e.") {
+	defer floatFormatBufPool.Put(bp)
-		return s
+
+	*bp = strconv.AppendFloat((*bp)[:0], f, 'g', -1, 64)
+	if bytes.ContainsAny(*bp, "e.") {
+		return string(*bp)
 	}
-	return s + ".0"
+	*bp = append(*bp, '.', '0')
+	return string(*bp)
 }
 
 // isNativeHistogram returns false iff the provided histograms has no spans at

model/textparse/protobufparse_test.go

@@ -409,6 +409,49 @@ metric: <
   >
 >
 
+`,
+		`name: "test_histogram3"
+help: "Similar histogram as before but now with integer buckets."
+type: HISTOGRAM
+metric: <
+  histogram: <
+    sample_count: 6
+    sample_sum: 50
+    bucket: <
+      cumulative_count: 2
+      upper_bound: -20
+    >
+    bucket: <
+      cumulative_count: 4
+      upper_bound: 20
+      exemplar: <
+        label: <
+          name: "dummyID"
+          value: "59727"
+        >
+        value: 15
+        timestamp: <
+          seconds: 1625851153
+          nanos: 146848499
+        >
+      >
+    >
+    bucket: <
+      cumulative_count: 6
+      upper_bound: 30
+      exemplar: <
+        label: <
+          name: "dummyID"
+          value: "5617"
+        >
+        value: 25
+      >
+    >
+    schema: 0
+    zero_threshold: 0
+  >
+>
+
 `,
 		`name: "test_histogram_family"
 help: "Test histogram metric family with two very simple histograms."
@@ -1050,6 +1093,66 @@ func TestProtobufParse(t *testing.T) {
 						"le", "+Inf",
 					),
 				},
+				{
+					m:    "test_histogram3",
+					help: "Similar histogram as before but now with integer buckets.",
+				},
+				{
+					m:   "test_histogram3",
+					typ: model.MetricTypeHistogram,
+				},
+				{
+					m: "test_histogram3_count",
+					v: 6,
+					lset: labels.FromStrings(
+						"__name__", "test_histogram3_count",
+					),
+				},
+				{
+					m: "test_histogram3_sum",
+					v: 50,
+					lset: labels.FromStrings(
+						"__name__", "test_histogram3_sum",
+					),
+				},
+				{
+					m: "test_histogram3_bucket\xffle\xff-20.0",
+					v: 2,
+					lset: labels.FromStrings(
+						"__name__", "test_histogram3_bucket",
+						"le", "-20.0",
+					),
+				},
+				{
+					m: "test_histogram3_bucket\xffle\xff20.0",
+					v: 4,
+					lset: labels.FromStrings(
+						"__name__", "test_histogram3_bucket",
+						"le", "20.0",
+					),
+					es: []exemplar.Exemplar{
+						{Labels: labels.FromStrings("dummyID", "59727"), Value: 15, HasTs: true, Ts: 1625851153146},
+					},
+				},
+				{
+					m: "test_histogram3_bucket\xffle\xff30.0",
+					v: 6,
+					lset: labels.FromStrings(
+						"__name__", "test_histogram3_bucket",
+						"le", "30.0",
+					),
+					es: []exemplar.Exemplar{
+						{Labels: labels.FromStrings("dummyID", "5617"), Value: 25, HasTs: false},
+					},
+				},
+				{
+					m: "test_histogram3_bucket\xffle\xff+Inf",
+					v: 6,
+					lset: labels.FromStrings(
+						"__name__", "test_histogram3_bucket",
+						"le", "+Inf",
+					),
+				},
 				{
 					m:    "test_histogram_family",
 					help: "Test histogram metric family with two very simple histograms.",
@@ -1857,6 +1960,66 @@ func TestProtobufParse(t *testing.T) {
 						"le", "+Inf",
 					),
 				},
+				{
+					m:    "test_histogram3",
+					help: "Similar histogram as before but now with integer buckets.",
+				},
+				{
+					m:   "test_histogram3",
+					typ: model.MetricTypeHistogram,
+				},
+				{
+					m: "test_histogram3_count",
+					v: 6,
+					lset: labels.FromStrings(
+						"__name__", "test_histogram3_count",
+					),
+				},
+				{
+					m: "test_histogram3_sum",
+					v: 50,
+					lset: labels.FromStrings(
+						"__name__", "test_histogram3_sum",
+					),
+				},
+				{
+					m: "test_histogram3_bucket\xffle\xff-20.0",
+					v: 2,
+					lset: labels.FromStrings(
+						"__name__", "test_histogram3_bucket",
+						"le", "-20.0",
+					),
+				},
+				{
+					m: "test_histogram3_bucket\xffle\xff20.0",
+					v: 4,
+					lset: labels.FromStrings(
+						"__name__", "test_histogram3_bucket",
+						"le", "20.0",
+					),
+					es: []exemplar.Exemplar{
+						{Labels: labels.FromStrings("dummyID", "59727"), Value: 15, HasTs: true, Ts: 1625851153146},
+					},
+				},
+				{
+					m: "test_histogram3_bucket\xffle\xff30.0",
+					v: 6,
+					lset: labels.FromStrings(
+						"__name__", "test_histogram3_bucket",
+						"le", "30.0",
+					),
+					es: []exemplar.Exemplar{
+						{Labels: labels.FromStrings("dummyID", "5617"), Value: 25, HasTs: false},
+					},
+				},
+				{
+					m: "test_histogram3_bucket\xffle\xff+Inf",
+					v: 6,
+					lset: labels.FromStrings(
+						"__name__", "test_histogram3_bucket",
+						"le", "+Inf",
+					),
+				},
 				{
 					m:    "test_histogram_family",
 					help: "Test histogram metric family with two very simple histograms.",