Merge branch 'main' into examples-best-practices

.github/CODEOWNERS

@@ -0,0 +1 @@
+* @ArthurSens @bwplotka @kakkoyun @vesari

.github/workflows/codeql-analysis.yml

@@ -46,11 +46,11 @@ jobs:
 
     steps:
     - name: Checkout repository
-      uses: actions/checkout@d632683dd7b4114ad314bca15554477dd762a938 # v4.2.0
+      uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
 
     # Initializes the CodeQL tools for scanning.
     - name: Initialize CodeQL
-      uses: github/codeql-action/init@e2b3eafc8d227b0241d48be5f425d47c2d750a13 # v3.26.10
+      uses: github/codeql-action/init@662472033e021d55d94146f66f6058822b0b39fd # v3.27.0
       with:
         languages: ${{ matrix.language }}
         # If you wish to specify custom queries, you can do so here or in a config file.
@@ -61,7 +61,7 @@ jobs:
     # Autobuild attempts to build any compiled languages  (C/C++, C#, or Java).
     # If this step fails, then you should remove it and run the build manually (see below)
     - name: Autobuild
-      uses: github/codeql-action/autobuild@e2b3eafc8d227b0241d48be5f425d47c2d750a13 # v3.26.10
+      uses: github/codeql-action/autobuild@662472033e021d55d94146f66f6058822b0b39fd # v3.27.0
 
     # ℹ️ Command-line programs to run using the OS shell.
     # 📚 https://git.io/JvXDl
@@ -75,4 +75,4 @@ jobs:
     #   make release
 
     - name: Perform CodeQL Analysis
-      uses: github/codeql-action/analyze@e2b3eafc8d227b0241d48be5f425d47c2d750a13 # v3.26.10
+      uses: github/codeql-action/analyze@662472033e021d55d94146f66f6058822b0b39fd # v3.27.0

.github/workflows/container_description.yml

@@ -18,7 +18,7 @@ jobs:
     if: github.repository_owner == 'prometheus' || github.repository_owner == 'prometheus-community' # Don't run this workflow on forks.
     steps:
       - name: git checkout
-        uses: actions/checkout@d632683dd7b4114ad314bca15554477dd762a938 # v4.2.0
+        uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
       - name: Set docker hub repo name
         run: echo "DOCKER_REPO_NAME=$(make docker-repo-name)" >> $GITHUB_ENV
       - name: Push README to Dockerhub
@@ -40,7 +40,7 @@ jobs:
     if: github.repository_owner == 'prometheus' || github.repository_owner == 'prometheus-community' # Don't run this workflow on forks.
     steps:
       - name: git checkout
-        uses: actions/checkout@d632683dd7b4114ad314bca15554477dd762a938 # v4.2.0
+        uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
       - name: Set quay.io org name
         run: echo "DOCKER_REPO=$(echo quay.io/${GITHUB_REPOSITORY_OWNER} | tr -d '-')" >> $GITHUB_ENV
       - name: Set quay.io repo name

.github/workflows/dagger-golangci-lint.yml

@@ -23,9 +23,9 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout repository
-        uses: actions/checkout@d632683dd7b4114ad314bca15554477dd762a938 # v4.2.0
+        uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
       - name: Lint
-        uses: dagger/dagger-for-github@fc945fa66fc7bfa72bc80f85b1a1ef4bd1d30cbb # v6.11.0
+        uses: dagger/dagger-for-github@ad6a4e308a42fb2cf9be8b060f9aba9d57d4c9aa # v6.14.0
         with:
           version: "latest"
           verb: call

.github/workflows/go.yml

@@ -24,7 +24,7 @@ jobs:
         supported_versions: ${{ steps.matrix.outputs.supported_versions }}
     steps:
       - name: Checkout code
-        uses: actions/checkout@d632683dd7b4114ad314bca15554477dd762a938 # v4.2.0
+        uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
       - name: Read supported_go_versions.txt
         id: matrix
         run: |
@@ -43,17 +43,17 @@ jobs:
 
     steps:
       - name: Checkout code
-        uses: actions/checkout@d632683dd7b4114ad314bca15554477dd762a938 # v4.2.0
+        uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
 
       - name: Run tests and check license
-        uses: dagger/dagger-for-github@fc945fa66fc7bfa72bc80f85b1a1ef4bd1d30cbb # v6.11.0
+        uses: dagger/dagger-for-github@ad6a4e308a42fb2cf9be8b060f9aba9d57d4c9aa # v6.14.0
         with:
           version: "latest"
           verb: call
           args: -vvv --src . make --go-version ${{matrix.go_version}} --args 'check_license test'
 
       - name: Run style and unused
-        uses: dagger/dagger-for-github@fc945fa66fc7bfa72bc80f85b1a1ef4bd1d30cbb # v6.11.0
+        uses: dagger/dagger-for-github@ad6a4e308a42fb2cf9be8b060f9aba9d57d4c9aa # v6.14.0
         if: ${{ matrix.go_version == '1.21' }}
         with:
           version: "latest"

.github/workflows/golangci-lint.yml

@@ -24,16 +24,16 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout repository
-        uses: actions/checkout@d632683dd7b4114ad314bca15554477dd762a938 # v4.2.0
+        uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
       - name: Install Go
-        uses: actions/setup-go@0a12ed9d6a96ab950c8f026ed9f722fe0da7ef32 # v5.0.2
+        uses: actions/setup-go@41dfa10bad2bb2ae585af6ee5bb4d7d973ad74ed # v5.1.0
         with:
           go-version: 1.23.x
       - name: Install snmp_exporter/generator dependencies
         run: sudo apt-get update && sudo apt-get -y install libsnmp-dev
         if: github.repository == 'prometheus/snmp_exporter'
       - name: Lint
-        uses: golangci/golangci-lint-action@aaa42aa0628b4ae2578232a66b541047968fac86 # v6.1.0
+        uses: golangci/golangci-lint-action@971e284b6050e8a5849b72094c50ab08da042db8 # v6.1.1
         with:
           args: --verbose
-          version: v1.60.2
+          version: v1.61.0

.github/workflows/update-go-versions.yml

@@ -13,7 +13,7 @@ jobs:
 
     steps:
       - name: Checkout repository
-        uses: actions/checkout@d632683dd7b4114ad314bca15554477dd762a938 # v4.2.0
+        uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
 
       - name: Execute bash script
         run: bash update-go-version.bash

.golangci.yml

@@ -25,11 +25,13 @@ linters:
     - ineffassign
     - misspell
     - nolintlint
+    - perfsprint
     - predeclared
     - revive
     - staticcheck
     - unconvert
     - unused
+    - usestdlibvars
     - wastedassign
 
 issues:
@@ -66,6 +68,17 @@ linters-settings:
     local-prefixes: github.com/prometheus/client_golang
   gofumpt:
     extra-rules: true
+  perfsprint:
+    # Optimizes even if it requires an int or uint type cast.
+    int-conversion: true
+    # Optimizes into `err.Error()` even if it is only equivalent for non-nil errors.
+    err-error: true
+    # Optimizes `fmt.Errorf`.
+    errorf: true
+    # Optimizes `fmt.Sprintf` with only one argument.
+    sprintf1: true
+    # Optimizes into strings concatenation.
+    strconcat: true
   revive:
     rules:
       # https://github.com/mgechev/revive/blob/master/RULES_DESCRIPTIONS.md#unused-parameter

CHANGELOG.md

@@ -1,5 +1,11 @@
 ## Unreleased
 
+## 1.20.5 / 2024-10-15
+
+* [BUGFIX] testutil: Reverted #1424; functions using compareMetricFamilies are (again) only failing if filtered metricNames are in the expected input.
+
+## 1.20.4 / 2024-09-07
+
 * [BUGFIX] histograms: Fix possible data race when appending exemplars vs metrics gather. #1623
 
 ## 1.20.3 / 2024-09-05
@@ -28,7 +34,7 @@
 * [FEATURE] promlint: Add duplicated metric lint rule. #1472
 * [BUGFIX] promlint: Relax metric type in name linter rule. #1455
 * [BUGFIX] promhttp: Make sure server instrumentation wrapping supports new and future extra responseWriter methods. #1480
-* [BUGFIX] testutil: Functions using compareMetricFamilies are now failing if filtered metricNames are not in the input. #1424
+* [BUGFIX] **breaking** testutil: Functions using compareMetricFamilies are now failing if filtered metricNames are not in the input. #1424 (reverted in 1.20.5)
 
 ## 1.19.0 / 2024-02-27
 

MAINTAINERS.md

@@ -1,3 +1,4 @@
+* Arianna Vespri <arianna.vespri@proton.me> @vesari
 * Arthur Silva Sens <arthursens2005@gmail.com> @ArthurSens
 * Bartłomiej Płotka <bwplotka@gmail.com> @bwplotka
 * Kemal Akkoyun <kakkoyun@gmail.com> @kakkoyun

Makefile.common

@@ -61,7 +61,7 @@ PROMU_URL     := https://github.com/prometheus/promu/releases/download/v$(PROMU_
 SKIP_GOLANGCI_LINT :=
 GOLANGCI_LINT :=
 GOLANGCI_LINT_OPTS ?=
-GOLANGCI_LINT_VERSION ?= v1.60.2
+GOLANGCI_LINT_VERSION ?= v1.61.0
 # golangci-lint only supports linux, darwin and windows platforms on i386/amd64/arm64.
 # windows isn't included here because of the path separator being different.
 ifeq ($(GOHOSTOS),$(filter $(GOHOSTOS),linux darwin))

VERSION

@@ -1 +1 @@
-1.20.2
+1.20.5

api/prometheus/v1/api_test.go

@@ -16,13 +16,13 @@ package v1
 import (
 	"context"
 	"errors"
-	"fmt"
 	"io"
 	"math"
 	"net/http"
 	"net/http/httptest"
 	"net/url"
 	"reflect"
+	"strconv"
 	"strings"
 	"testing"
 	"time"
@@ -260,7 +260,7 @@ func TestAPIs(t *testing.T) {
 		},
 		{
 			do:    doQuery("2", testTime),
-			inErr: fmt.Errorf("some error"),
+			inErr: errors.New("some error"),
 
 			reqMethod: "POST",
 			reqPath:   "/api/v1/query",
@@ -336,7 +336,7 @@ func TestAPIs(t *testing.T) {
 				End:   testTime,
 				Step:  1 * time.Minute,
 			}, WithTimeout(5*time.Second)),
-			inErr: fmt.Errorf("some error"),
+			inErr: errors.New("some error"),
 
 			reqMethod: "POST",
 			reqPath:   "/api/v1/query_range",
@@ -361,14 +361,14 @@ func TestAPIs(t *testing.T) {
 
 		{
 			do:        doLabelNames(nil, testTime.Add(-100*time.Hour), testTime),
-			inErr:     fmt.Errorf("some error"),
+			inErr:     errors.New("some error"),
 			reqMethod: "POST",
 			reqPath:   "/api/v1/labels",
 			err:       errors.New("some error"),
 		},
 		{
 			do:         doLabelNames(nil, testTime.Add(-100*time.Hour), testTime),
-			inErr:      fmt.Errorf("some error"),
+			inErr:      errors.New("some error"),
 			inWarnings: []string{"a"},
 			reqMethod:  "POST",
 			reqPath:    "/api/v1/labels",
@@ -400,14 +400,14 @@ func TestAPIs(t *testing.T) {
 
 		{
 			do:        doLabelValues(nil, "mylabel", testTime.Add(-100*time.Hour), testTime),
-			inErr:     fmt.Errorf("some error"),
+			inErr:     errors.New("some error"),
 			reqMethod: "GET",
 			reqPath:   "/api/v1/label/mylabel/values",
 			err:       errors.New("some error"),
 		},
 		{
 			do:         doLabelValues(nil, "mylabel", testTime.Add(-100*time.Hour), testTime),
-			inErr:      fmt.Errorf("some error"),
+			inErr:      errors.New("some error"),
 			inWarnings: []string{"a"},
 			reqMethod:  "GET",
 			reqPath:    "/api/v1/label/mylabel/values",
@@ -464,7 +464,7 @@ func TestAPIs(t *testing.T) {
 
 		{
 			do:        doSeries("up", testTime.Add(-time.Minute), testTime),
-			inErr:     fmt.Errorf("some error"),
+			inErr:     errors.New("some error"),
 			reqMethod: "POST",
 			reqPath:   "/api/v1/series",
 			err:       errors.New("some error"),
@@ -472,7 +472,7 @@ func TestAPIs(t *testing.T) {
 		// Series with error and warning.
 		{
 			do:         doSeries("up", testTime.Add(-time.Minute), testTime),
-			inErr:      fmt.Errorf("some error"),
+			inErr:      errors.New("some error"),
 			inWarnings: []string{"a"},
 			reqMethod:  "POST",
 			reqPath:    "/api/v1/series",
@@ -493,7 +493,7 @@ func TestAPIs(t *testing.T) {
 
 		{
 			do:        doSnapshot(true),
-			inErr:     fmt.Errorf("some error"),
+			inErr:     errors.New("some error"),
 			reqMethod: "POST",
 			reqPath:   "/api/v1/admin/tsdb/snapshot",
 			err:       errors.New("some error"),
@@ -507,7 +507,7 @@ func TestAPIs(t *testing.T) {
 
 		{
 			do:        doCleanTombstones(),
-			inErr:     fmt.Errorf("some error"),
+			inErr:     errors.New("some error"),
 			reqMethod: "POST",
 			reqPath:   "/api/v1/admin/tsdb/clean_tombstones",
 			err:       errors.New("some error"),
@@ -528,7 +528,7 @@ func TestAPIs(t *testing.T) {
 
 		{
 			do:        doDeleteSeries("up", testTime.Add(-time.Minute), testTime),
-			inErr:     fmt.Errorf("some error"),
+			inErr:     errors.New("some error"),
 			reqMethod: "POST",
 			reqPath:   "/api/v1/admin/tsdb/delete_series",
 			err:       errors.New("some error"),
@@ -550,8 +550,8 @@ func TestAPIs(t *testing.T) {
 			do:        doConfig(),
 			reqMethod: "GET",
 			reqPath:   "/api/v1/status/config",
-			inErr:     fmt.Errorf("some error"),
-			err:       fmt.Errorf("some error"),
+			inErr:     errors.New("some error"),
+			err:       errors.New("some error"),
 		},
 
 		{
@@ -578,16 +578,16 @@ func TestAPIs(t *testing.T) {
 			do:        doFlags(),
 			reqMethod: "GET",
 			reqPath:   "/api/v1/status/flags",
-			inErr:     fmt.Errorf("some error"),
-			err:       fmt.Errorf("some error"),
+			inErr:     errors.New("some error"),
+			err:       errors.New("some error"),
 		},
 
 		{
 			do:        doBuildinfo(),
 			reqMethod: "GET",
 			reqPath:   "/api/v1/status/buildinfo",
-			inErr:     fmt.Errorf("some error"),
-			err:       fmt.Errorf("some error"),
+			inErr:     errors.New("some error"),
+			err:       errors.New("some error"),
 		},
 
 		{
@@ -616,8 +616,8 @@ func TestAPIs(t *testing.T) {
 			do:        doRuntimeinfo(),
 			reqMethod: "GET",
 			reqPath:   "/api/v1/status/runtimeinfo",
-			inErr:     fmt.Errorf("some error"),
-			err:       fmt.Errorf("some error"),
+			inErr:     errors.New("some error"),
+			err:       errors.New("some error"),
 		},
 
 		{
@@ -684,8 +684,8 @@ func TestAPIs(t *testing.T) {
 			do:        doAlertManagers(),
 			reqMethod: "GET",
 			reqPath:   "/api/v1/alertmanagers",
-			inErr:     fmt.Errorf("some error"),
-			err:       fmt.Errorf("some error"),
+			inErr:     errors.New("some error"),
+			err:       errors.New("some error"),
 		},
 
 		{
@@ -891,8 +891,8 @@ func TestAPIs(t *testing.T) {
 			do:        doRules(),
 			reqMethod: "GET",
 			reqPath:   "/api/v1/rules",
-			inErr:     fmt.Errorf("some error"),
-			err:       fmt.Errorf("some error"),
+			inErr:     errors.New("some error"),
+			err:       errors.New("some error"),
 		},
 
 		{
@@ -971,8 +971,8 @@ func TestAPIs(t *testing.T) {
 			do:        doTargets(),
 			reqMethod: "GET",
 			reqPath:   "/api/v1/targets",
-			inErr:     fmt.Errorf("some error"),
-			err:       fmt.Errorf("some error"),
+			inErr:     errors.New("some error"),
+			err:       errors.New("some error"),
 		},
 
 		{
@@ -1005,7 +1005,7 @@ func TestAPIs(t *testing.T) {
 
 		{
 			do:        doTargetsMetadata("{job=\"prometheus\"}", "go_goroutines", "1"),
-			inErr:     fmt.Errorf("some error"),
+			inErr:     errors.New("some error"),
 			reqMethod: "GET",
 			reqPath:   "/api/v1/targets/metadata",
 			err:       errors.New("some error"),
@@ -1037,7 +1037,7 @@ func TestAPIs(t *testing.T) {
 
 		{
 			do:        doMetadata("", "1"),
-			inErr:     fmt.Errorf("some error"),
+			inErr:     errors.New("some error"),
 			reqMethod: "GET",
 			reqPath:   "/api/v1/metadata",
 			err:       errors.New("some error"),
@@ -1047,8 +1047,8 @@ func TestAPIs(t *testing.T) {
 			do:        doTSDB(),
 			reqMethod: "GET",
 			reqPath:   "/api/v1/status/tsdb",
-			inErr:     fmt.Errorf("some error"),
-			err:       fmt.Errorf("some error"),
+			inErr:     errors.New("some error"),
+			err:       errors.New("some error"),
 		},
 
 		{
@@ -1127,8 +1127,8 @@ func TestAPIs(t *testing.T) {
 			do:        doWalReply(),
 			reqMethod: "GET",
 			reqPath:   "/api/v1/status/walreplay",
-			inErr:     fmt.Errorf("some error"),
-			err:       fmt.Errorf("some error"),
+			inErr:     errors.New("some error"),
+			err:       errors.New("some error"),
 		},
 
 		{
@@ -1212,7 +1212,7 @@ func TestAPIs(t *testing.T) {
 	tests = append(tests, queryTests...)
 
 	for i, test := range tests {
-		t.Run(fmt.Sprintf("%d", i), func(t *testing.T) {
+		t.Run(strconv.Itoa(i), func(t *testing.T) {
 			tc.curTest = test
 
 			res, warnings, err := test.do()
@@ -1430,7 +1430,7 @@ func TestAPIClientDo(t *testing.T) {
 	}
 
 	for i, test := range tests {
-		t.Run(fmt.Sprintf("%d", i), func(t *testing.T) {
+		t.Run(strconv.Itoa(i), func(t *testing.T) {
 			tc.ch <- test
 
 			_, body, warnings, err := client.Do(context.Background(), tc.req)

api/prometheus/v1/example_test.go

@@ -199,6 +199,45 @@ func ExampleAPI_queryRangeWithAuthBearerToken() {
 	fmt.Printf("Result:\n%v\n", result)
 }
 
+func ExampleAPI_queryRangeWithAuthBearerTokenHeadersRoundTripper() {
+	client, err := api.NewClient(api.Config{
+		Address: "http://demo.robustperception.io:9090",
+		// We can use amazing github.com/prometheus/common/config helper!
+		RoundTripper: config.NewHeadersRoundTripper(
+			&config.Headers{
+				Headers: map[string]config.Header{
+					"Authorization": {
+						Values: []string{"Bearer secret"},
+					},
+				},
+			},
+			api.DefaultRoundTripper,
+		),
+	})
+	if err != nil {
+		fmt.Printf("Error creating client: %v\n", err)
+		os.Exit(1)
+	}
+
+	v1api := v1.NewAPI(client)
+	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+	defer cancel()
+	r := v1.Range{
+		Start: time.Now().Add(-time.Hour),
+		End:   time.Now(),
+		Step:  time.Minute,
+	}
+	result, warnings, err := v1api.QueryRange(ctx, "rate(prometheus_tsdb_head_samples_appended_total[5m])", r)
+	if err != nil {
+		fmt.Printf("Error querying Prometheus: %v\n", err)
+		os.Exit(1)
+	}
+	if len(warnings) > 0 {
+		fmt.Printf("Warnings: %v\n", warnings)
+	}
+	fmt.Printf("Result:\n%v\n", result)
+}
+
 func ExampleAPI_series() {
 	client, err := api.NewClient(api.Config{
 		Address: "http://demo.robustperception.io:9090",

examples/exemplars/main.go

@@ -17,10 +17,10 @@
 package main
 
 import (
-	"fmt"
 	"log"
 	"math/rand"
 	"net/http"
+	"strconv"
 	"time"
 
 	"github.com/prometheus/client_golang/prometheus"
@@ -50,7 +50,7 @@ func main() {
 			// Record fictional latency.
 			now := time.Now()
 			requestDurations.(prometheus.ExemplarObserver).ObserveWithExemplar(
-				time.Since(now).Seconds(), prometheus.Labels{"dummyID": fmt.Sprint(rand.Intn(100000))},
+				time.Since(now).Seconds(), prometheus.Labels{"dummyID": strconv.Itoa(rand.Intn(100000))},
 			)
 			time.Sleep(600 * time.Millisecond)
 		}

examples/random/main.go

@@ -18,11 +18,11 @@ package main
 
 import (
 	"flag"
-	"fmt"
 	"log"
 	"math"
 	"math/rand"
 	"net/http"
+	"strconv"
 	"time"
 
 	"github.com/prometheus/client_golang/prometheus"
@@ -116,7 +116,7 @@ func main() {
 			// the ExemplarObserver interface and thus don't need to
 			// check the outcome of the type assertion.
 			m.rpcDurationsHistogram.(prometheus.ExemplarObserver).ObserveWithExemplar(
-				v, prometheus.Labels{"dummyID": fmt.Sprint(rand.Intn(100000))},
+				v, prometheus.Labels{"dummyID": strconv.Itoa(rand.Intn(100000))},
 			)
 			time.Sleep(time.Duration(75*oscillationFactor()) * time.Millisecond)
 		}

go.mod

@@ -7,13 +7,13 @@ require (
 	github.com/cespare/xxhash/v2 v2.3.0
 	github.com/google/go-cmp v0.6.0
 	github.com/json-iterator/go v1.1.12
-	github.com/klauspost/compress v1.17.10
+	github.com/klauspost/compress v1.17.11
 	github.com/kylelemons/godebug v1.1.0
 	github.com/prometheus/client_model v0.6.1
-	github.com/prometheus/common v0.59.1
+	github.com/prometheus/common v0.60.1
 	github.com/prometheus/procfs v0.15.1
-	golang.org/x/sys v0.25.0
-	google.golang.org/protobuf v1.34.2
+	golang.org/x/sys v0.26.0
+	google.golang.org/protobuf v1.35.1
 )
 
 require (
@@ -23,9 +23,9 @@ require (
 	github.com/modern-go/reflect2 v1.0.2 // indirect
 	github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822 // indirect
 	github.com/mwitkow/go-conntrack v0.0.0-20190716064945-2f068394615f // indirect
-	golang.org/x/net v0.28.0 // indirect
-	golang.org/x/oauth2 v0.22.0 // indirect
-	golang.org/x/text v0.17.0 // indirect
+	golang.org/x/net v0.29.0 // indirect
+	golang.org/x/oauth2 v0.23.0 // indirect
+	golang.org/x/text v0.18.0 // indirect
 	gopkg.in/yaml.v2 v2.4.0 // indirect
 )
 

go.sum

@@ -13,8 +13,8 @@ github.com/jpillora/backoff v1.0.0 h1:uvFg412JmmHBHw7iwprIxkPMI+sGQ4kzOWsMeHnm2E
 github.com/jpillora/backoff v1.0.0/go.mod h1:J/6gKK9jxlEcS3zixgDgUAsiuZ7yrSoa/FX5e0EB2j4=
 github.com/json-iterator/go v1.1.12 h1:PV8peI4a0ysnczrg+LtxykD8LfKY9ML6u2jnxaEnrnM=
 github.com/json-iterator/go v1.1.12/go.mod h1:e30LSqwooZae/UwlEbR2852Gd8hjQvJoHmT4TnhNGBo=
-github.com/klauspost/compress v1.17.10 h1:oXAz+Vh0PMUvJczoi+flxpnBEPxoER1IaAnU/NMPtT0=
-github.com/klauspost/compress v1.17.10/go.mod h1:pMDklpSncoRMuLFrf1W9Ss9KT+0rH90U12bZKk7uwG0=
+github.com/klauspost/compress v1.17.11 h1:In6xLpyWOi1+C7tXUUWv2ot1QvBjxevKAaI6IXrJmUc=
+github.com/klauspost/compress v1.17.11/go.mod h1:pMDklpSncoRMuLFrf1W9Ss9KT+0rH90U12bZKk7uwG0=
 github.com/kr/pretty v0.3.1 h1:flRD4NNwYAUpkphVc1HcthR4KEIFJ65n8Mw5qdRn3LE=
 github.com/kr/pretty v0.3.1/go.mod h1:hoEshYVHaxMs3cyo3Yncou5ZscifuDolrwPKZanG3xk=
 github.com/kr/text v0.2.0 h1:5Nx0Ya0ZqY2ygV366QzturHI13Jq95ApcVaJBhpS+AY=
@@ -35,8 +35,8 @@ github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZb
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/prometheus/client_model v0.6.1 h1:ZKSh/rekM+n3CeS952MLRAdFwIKqeY8b62p8ais2e9E=
 github.com/prometheus/client_model v0.6.1/go.mod h1:OrxVMOVHjw3lKMa8+x6HeMGkHMQyHDk9E3jmP2AmGiY=
-github.com/prometheus/common v0.59.1 h1:LXb1quJHWm1P6wq/U824uxYi4Sg0oGvNeUm1z5dJoX0=
-github.com/prometheus/common v0.59.1/go.mod h1:GpWM7dewqmVYcd7SmRaiWVe9SSqjf0UrwnYnpEZNuT0=
+github.com/prometheus/common v0.60.1 h1:FUas6GcOw66yB/73KC+BOZoFJmbo/1pojoILArPAaSc=
+github.com/prometheus/common v0.60.1/go.mod h1:h0LYf1R1deLSKtD4Vdg8gy4RuOvENW2J/h19V5NADQw=
 github.com/prometheus/procfs v0.15.1 h1:YagwOFzUgYfKKHX6Dr+sHT7km/hxC76UB0learggepc=
 github.com/prometheus/procfs v0.15.1/go.mod h1:fB45yRUv8NstnjriLhBQLuOUt+WW4BsoGhij/e3PBqk=
 github.com/rogpeppe/go-internal v1.9.0/go.mod h1:WtVeX8xhTBvf0smdhujwtBcq4Qrzq/fJaraNFVN+nFs=
@@ -46,16 +46,16 @@ github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+
 github.com/stretchr/testify v1.3.0/go.mod h1:M5WIy9Dh21IEIfnGCwXGc5bZfKNJtfHm1UVUgZn+9EI=
 github.com/stretchr/testify v1.9.0 h1:HtqpIVDClZ4nwg75+f6Lvsy/wHu+3BoSGCbBAcpTsTg=
 github.com/stretchr/testify v1.9.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
-golang.org/x/net v0.28.0 h1:a9JDOJc5GMUJ0+UDqmLT86WiEy7iWyIhz8gz8E4e5hE=
-golang.org/x/net v0.28.0/go.mod h1:yqtgsTWOOnlGLG9GFRrK3++bGOUEkNBoHZc8MEDWPNg=
-golang.org/x/oauth2 v0.22.0 h1:BzDx2FehcG7jJwgWLELCdmLuxk2i+x9UDpSiss2u0ZA=
-golang.org/x/oauth2 v0.22.0/go.mod h1:XYTD2NtWslqkgxebSiOHnXEap4TF09sJSc7H1sXbhtI=
-golang.org/x/sys v0.25.0 h1:r+8e+loiHxRqhXVl6ML1nO3l1+oFoWbnlu2Ehimmi34=
-golang.org/x/sys v0.25.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
-golang.org/x/text v0.17.0 h1:XtiM5bkSOt+ewxlOE/aE/AKEHibwj/6gvWMl9Rsh0Qc=
-golang.org/x/text v0.17.0/go.mod h1:BuEKDfySbSR4drPmRPG/7iBdf8hvFMuRexcpahXilzY=
-google.golang.org/protobuf v1.34.2 h1:6xV6lTsCfpGD21XK49h7MhtcApnLqkfYgPcdHftf6hg=
-google.golang.org/protobuf v1.34.2/go.mod h1:qYOHts0dSfpeUzUFpOMr/WGzszTmLH+DiWniOlNbLDw=
+golang.org/x/net v0.29.0 h1:5ORfpBpCs4HzDYoodCDBbwHzdR5UrLBZ3sOnUJmFoHo=
+golang.org/x/net v0.29.0/go.mod h1:gLkgy8jTGERgjzMic6DS9+SP0ajcu6Xu3Orq/SpETg0=
+golang.org/x/oauth2 v0.23.0 h1:PbgcYx2W7i4LvjJWEbf0ngHV6qJYr86PkAV3bXdLEbs=
+golang.org/x/oauth2 v0.23.0/go.mod h1:XYTD2NtWslqkgxebSiOHnXEap4TF09sJSc7H1sXbhtI=
+golang.org/x/sys v0.26.0 h1:KHjCJyddX0LoSTb3J+vWpupP9p0oznkqVk/IfjymZbo=
+golang.org/x/sys v0.26.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
+golang.org/x/text v0.18.0 h1:XvMDiNzPAl0jr17s6W9lcaIhGUfUORdGCNsuLmPG224=
+golang.org/x/text v0.18.0/go.mod h1:BuEKDfySbSR4drPmRPG/7iBdf8hvFMuRexcpahXilzY=
+google.golang.org/protobuf v1.35.1 h1:m3LfL6/Ca+fqnjnlqQXNpFPABW1UD7mjh8KO2mKFytA=
+google.golang.org/protobuf v1.35.1/go.mod h1:9fA7Ob0pmnwhb644+1+CVWFRbNajQ6iRojtC/QF5bRE=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c h1:Hei/4ADfdWqJk1ZMxUNpqntNwaWcugrBjAiHlqqRiVk=
 gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c/go.mod h1:JHkPIbrfpd72SG/EVd6muEfDQjcINNoR0C8j2r3qZ4Q=

prometheus/atomic_update.go

@@ -0,0 +1,50 @@
+// Copyright 2014 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.
+
+package prometheus
+
+import (
+	"math"
+	"sync/atomic"
+	"time"
+)
+
+// atomicUpdateFloat atomically updates the float64 value pointed to by bits
+// using the provided updateFunc, with an exponential backoff on contention.
+func atomicUpdateFloat(bits *uint64, updateFunc func(float64) float64) {
+	const (
+		// both numbers are derived from empirical observations
+		// documented in this PR: https://github.com/prometheus/client_golang/pull/1661
+		maxBackoff     = 320 * time.Millisecond
+		initialBackoff = 10 * time.Millisecond
+	)
+	backoff := initialBackoff
+
+	for {
+		loadedBits := atomic.LoadUint64(bits)
+		oldFloat := math.Float64frombits(loadedBits)
+		newFloat := updateFunc(oldFloat)
+		newBits := math.Float64bits(newFloat)
+
+		if atomic.CompareAndSwapUint64(bits, loadedBits, newBits) {
+			break
+		} else {
+			// Exponential backoff with sleep and cap to avoid infinite wait
+			time.Sleep(backoff)
+			backoff *= 2
+			if backoff > maxBackoff {
+				backoff = maxBackoff
+			}
+		}
+	}
+}

prometheus/atomic_update_test.go

@@ -0,0 +1,167 @@
+// Copyright 2014 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.
+
+package prometheus
+
+import (
+	"math"
+	"sync"
+	"sync/atomic"
+	"testing"
+	"unsafe"
+)
+
+var output float64
+
+func TestAtomicUpdateFloat(t *testing.T) {
+	var val float64 = 0.0
+	bits := (*uint64)(unsafe.Pointer(&val))
+	var wg sync.WaitGroup
+	numGoroutines := 100000
+	increment := 1.0
+
+	for i := 0; i < numGoroutines; i++ {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			atomicUpdateFloat(bits, func(f float64) float64 {
+				return f + increment
+			})
+		}()
+	}
+
+	wg.Wait()
+	expected := float64(numGoroutines) * increment
+	if val != expected {
+		t.Errorf("Expected %f, got %f", expected, val)
+	}
+}
+
+// Benchmark for atomicUpdateFloat with single goroutine (no contention).
+func BenchmarkAtomicUpdateFloat_SingleGoroutine(b *testing.B) {
+	var val float64 = 0.0
+	bits := (*uint64)(unsafe.Pointer(&val))
+
+	for i := 0; i < b.N; i++ {
+		atomicUpdateFloat(bits, func(f float64) float64 {
+			return f + 1.0
+		})
+	}
+
+	output = val
+}
+
+// Benchmark for old implementation with single goroutine (no contention) -> to check overhead of backoff
+func BenchmarkAtomicNoBackoff_SingleGoroutine(b *testing.B) {
+	var val float64 = 0.0
+	bits := (*uint64)(unsafe.Pointer(&val))
+
+	for i := 0; i < b.N; i++ {
+		for {
+			loadedBits := atomic.LoadUint64(bits)
+			newBits := math.Float64bits(math.Float64frombits(loadedBits) + 1.0)
+			if atomic.CompareAndSwapUint64(bits, loadedBits, newBits) {
+				break
+			}
+		}
+	}
+
+	output = val
+}
+
+// Benchmark varying the number of goroutines.
+func benchmarkAtomicUpdateFloatConcurrency(b *testing.B, numGoroutines int) {
+	var val float64 = 0.0
+	bits := (*uint64)(unsafe.Pointer(&val))
+	b.SetParallelism(numGoroutines)
+
+	b.ResetTimer()
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			atomicUpdateFloat(bits, func(f float64) float64 {
+				return f + 1.0
+			})
+		}
+	})
+
+	output = val
+}
+
+func benchmarkAtomicNoBackoffFloatConcurrency(b *testing.B, numGoroutines int) {
+	var val float64 = 0.0
+	bits := (*uint64)(unsafe.Pointer(&val))
+	b.SetParallelism(numGoroutines)
+
+	b.ResetTimer()
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			for {
+				loadedBits := atomic.LoadUint64(bits)
+				newBits := math.Float64bits(math.Float64frombits(loadedBits) + 1.0)
+				if atomic.CompareAndSwapUint64(bits, loadedBits, newBits) {
+					break
+				}
+			}
+		}
+	})
+
+	output = val
+}
+
+func BenchmarkAtomicUpdateFloat_1Goroutine(b *testing.B) {
+	benchmarkAtomicUpdateFloatConcurrency(b, 1)
+}
+
+func BenchmarkAtomicNoBackoff_1Goroutine(b *testing.B) {
+	benchmarkAtomicNoBackoffFloatConcurrency(b, 1)
+}
+
+func BenchmarkAtomicUpdateFloat_2Goroutines(b *testing.B) {
+	benchmarkAtomicUpdateFloatConcurrency(b, 2)
+}
+
+func BenchmarkAtomicNoBackoff_2Goroutines(b *testing.B) {
+	benchmarkAtomicNoBackoffFloatConcurrency(b, 2)
+}
+
+func BenchmarkAtomicUpdateFloat_4Goroutines(b *testing.B) {
+	benchmarkAtomicUpdateFloatConcurrency(b, 4)
+}
+
+func BenchmarkAtomicNoBackoff_4Goroutines(b *testing.B) {
+	benchmarkAtomicNoBackoffFloatConcurrency(b, 4)
+}
+
+func BenchmarkAtomicUpdateFloat_8Goroutines(b *testing.B) {
+	benchmarkAtomicUpdateFloatConcurrency(b, 8)
+}
+
+func BenchmarkAtomicNoBackoff_8Goroutines(b *testing.B) {
+	benchmarkAtomicNoBackoffFloatConcurrency(b, 8)
+}
+
+func BenchmarkAtomicUpdateFloat_16Goroutines(b *testing.B) {
+	benchmarkAtomicUpdateFloatConcurrency(b, 16)
+}
+
+func BenchmarkAtomicNoBackoff_16Goroutines(b *testing.B) {
+	benchmarkAtomicNoBackoffFloatConcurrency(b, 16)
+}
+
+func BenchmarkAtomicUpdateFloat_32Goroutines(b *testing.B) {
+	benchmarkAtomicUpdateFloatConcurrency(b, 32)
+}
+
+func BenchmarkAtomicNoBackoff_32Goroutines(b *testing.B) {
+	benchmarkAtomicNoBackoffFloatConcurrency(b, 32)
+}

prometheus/counter.go

@@ -134,13 +134,9 @@ func (c *counter) Add(v float64) {
 		return
 	}
 
-	for {
-		oldBits := atomic.LoadUint64(&c.valBits)
-		newBits := math.Float64bits(math.Float64frombits(oldBits) + v)
-		if atomic.CompareAndSwapUint64(&c.valBits, oldBits, newBits) {
-			return
-		}
-	}
+	atomicUpdateFloat(&c.valBits, func(oldVal float64) float64 {
+		return oldVal + v
+	})
 }
 
 func (c *counter) AddWithExemplar(v float64, e Labels) {

prometheus/counter_test.go

@@ -14,7 +14,6 @@
 package prometheus
 
 import (
-	"fmt"
 	"math"
 	"strings"
 	"testing"
@@ -120,10 +119,10 @@ func TestCounterVecGetMetricWithInvalidLabelValues(t *testing.T) {
 
 		expectPanic(t, func() {
 			counterVec.WithLabelValues(labelValues...)
-		}, fmt.Sprintf("WithLabelValues: expected panic because: %s", test.desc))
+		}, "WithLabelValues: expected panic because: "+test.desc)
 		expectPanic(t, func() {
 			counterVec.With(test.labels)
-		}, fmt.Sprintf("WithLabelValues: expected panic because: %s", test.desc))
+		}, "WithLabelValues: expected panic because: "+test.desc)
 
 		if _, err := counterVec.GetMetricWithLabelValues(labelValues...); err == nil {
 			t.Errorf("GetMetricWithLabelValues: expected error because: %s", test.desc)

prometheus/gauge.go

@@ -120,13 +120,9 @@ func (g *gauge) Dec() {
 }
 
 func (g *gauge) Add(val float64) {
-	for {
-		oldBits := atomic.LoadUint64(&g.valBits)
-		newBits := math.Float64bits(math.Float64frombits(oldBits) + val)
-		if atomic.CompareAndSwapUint64(&g.valBits, oldBits, newBits) {
-			return
-		}
-	}
+	atomicUpdateFloat(&g.valBits, func(oldVal float64) float64 {
+		return oldVal + val
+	})
 }
 
 func (g *gauge) Sub(val float64) {

prometheus/histogram.go

@@ -14,6 +14,7 @@
 package prometheus
 
 import (
+	"errors"
 	"fmt"
 	"math"
 	"runtime"
@@ -28,6 +29,11 @@ import (
 	"google.golang.org/protobuf/types/known/timestamppb"
 )
 
+const (
+	nativeHistogramSchemaMaximum = 8
+	nativeHistogramSchemaMinimum = -4
+)
+
 // nativeHistogramBounds for the frac of observed values. Only relevant for
 // schema > 0. The position in the slice is the schema. (0 is never used, just
 // here for convenience of using the schema directly as the index.)
@@ -858,15 +864,35 @@ func (h *histogram) Write(out *dto.Metric) error {
 // findBucket returns the index of the bucket for the provided value, or
 // len(h.upperBounds) for the +Inf bucket.
 func (h *histogram) findBucket(v float64) int {
-	// TODO(beorn7): For small numbers of buckets (<30), a linear search is
-	// slightly faster than the binary search. If we really care, we could
-	// switch from one search strategy to the other depending on the number
-	// of buckets.
-	//
-	// Microbenchmarks (BenchmarkHistogramNoLabels):
-	// 11 buckets: 38.3 ns/op linear - binary 48.7 ns/op
-	// 100 buckets: 78.1 ns/op linear - binary 54.9 ns/op
-	// 300 buckets: 154 ns/op linear - binary 61.6 ns/op
+	n := len(h.upperBounds)
+	if n == 0 {
+		return 0
+	}
+
+	// Early exit: if v is less than or equal to the first upper bound, return 0
+	if v <= h.upperBounds[0] {
+		return 0
+	}
+
+	// Early exit: if v is greater than the last upper bound, return len(h.upperBounds)
+	if v > h.upperBounds[n-1] {
+		return n
+	}
+
+	// For small arrays, use simple linear search
+	// "magic number" 35 is result of tests on couple different (AWS and baremetal) servers
+	// see more details here: https://github.com/prometheus/client_golang/pull/1662
+	if n < 35 {
+		for i, bound := range h.upperBounds {
+			if v <= bound {
+				return i
+			}
+		}
+		// If v is greater than all upper bounds, return len(h.upperBounds)
+		return n
+	}
+
+	// For larger arrays, use stdlib's binary search
 	return sort.SearchFloat64s(h.upperBounds, v)
 }
 
@@ -1440,9 +1466,9 @@ func pickSchema(bucketFactor float64) int32 {
 	floor := math.Floor(math.Log2(math.Log2(bucketFactor)))
 	switch {
 	case floor <= -8:
-		return 8
+		return nativeHistogramSchemaMaximum
 	case floor >= 4:
-		return -4
+		return nativeHistogramSchemaMinimum
 	default:
 		return -int32(floor)
 	}
@@ -1621,13 +1647,9 @@ func waitForCooldown(count uint64, counts *histogramCounts) {
 // atomicAddFloat adds the provided float atomically to another float
 // represented by the bit pattern the bits pointer is pointing to.
 func atomicAddFloat(bits *uint64, v float64) {
-	for {
-		loadedBits := atomic.LoadUint64(bits)
-		newBits := math.Float64bits(math.Float64frombits(loadedBits) + v)
-		if atomic.CompareAndSwapUint64(bits, loadedBits, newBits) {
-			break
-		}
-	}
+	atomicUpdateFloat(bits, func(oldVal float64) float64 {
+		return oldVal + v
+	})
 }
 
 // atomicDecUint32 atomically decrements the uint32 p points to.  See
@@ -1835,3 +1857,196 @@ func (n *nativeExemplars) addExemplar(e *dto.Exemplar) {
 		n.exemplars = append(n.exemplars[:nIdx], append([]*dto.Exemplar{e}, append(n.exemplars[nIdx:rIdx], n.exemplars[rIdx+1:]...)...)...)
 	}
 }
+
+type constNativeHistogram struct {
+	desc *Desc
+	dto.Histogram
+	labelPairs []*dto.LabelPair
+}
+
+func validateCount(sum float64, count uint64, negativeBuckets, positiveBuckets map[int]int64, zeroBucket uint64) error {
+	var bucketPopulationSum int64
+	for _, v := range positiveBuckets {
+		bucketPopulationSum += v
+	}
+	for _, v := range negativeBuckets {
+		bucketPopulationSum += v
+	}
+	bucketPopulationSum += int64(zeroBucket)
+
+	// If the sum of observations is NaN, the number of observations must be greater or equal to the sum of all bucket counts.
+	// Otherwise, the number of observations must be equal to the sum of all bucket counts .
+
+	if math.IsNaN(sum) && bucketPopulationSum > int64(count) ||
+		!math.IsNaN(sum) && bucketPopulationSum != int64(count) {
+		return errors.New("the sum of all bucket populations exceeds the count of observations")
+	}
+	return nil
+}
+
+// NewConstNativeHistogram returns a metric representing a Prometheus native histogram with
+// fixed values for the count, sum, and positive/negative/zero bucket counts. As those parameters
+// cannot be changed, the returned value does not implement the Histogram
+// interface (but only the Metric interface). Users of this package will not
+// have much use for it in regular operations. However, when implementing custom
+// OpenTelemetry Collectors, it is useful as a throw-away metric that is generated on the fly
+// to send it to Prometheus in the Collect method.
+//
+// zeroBucket counts all (positive and negative)
+// observations in the zero bucket (with an absolute value less or equal
+// the current threshold).
+// positiveBuckets and negativeBuckets are separate maps for negative and positive
+// observations. The map's value is an int64, counting observations in
+// that bucket. The map's key is the
+// index of the bucket according to the used
+// Schema. Index 0 is for an upper bound of 1 in positive buckets and for a lower bound of -1 in negative buckets.
+// NewConstNativeHistogram returns an error if
+//   - the length of labelValues is not consistent with the variable labels in Desc or if Desc is invalid.
+//   - the schema passed is not between 8 and -4
+//   - the sum of counts in all buckets including the zero bucket does not equal the count if sum is not NaN (or exceeds the count if sum is NaN)
+//
+// See https://opentelemetry.io/docs/specs/otel/compatibility/prometheus_and_openmetrics/#exponential-histograms for more details about the conversion from OTel to Prometheus.
+func NewConstNativeHistogram(
+	desc *Desc,
+	count uint64,
+	sum float64,
+	positiveBuckets, negativeBuckets map[int]int64,
+	zeroBucket uint64,
+	schema int32,
+	zeroThreshold float64,
+	createdTimestamp time.Time,
+	labelValues ...string,
+) (Metric, error) {
+	if desc.err != nil {
+		return nil, desc.err
+	}
+	if err := validateLabelValues(labelValues, len(desc.variableLabels.names)); err != nil {
+		return nil, err
+	}
+	if schema > nativeHistogramSchemaMaximum || schema < nativeHistogramSchemaMinimum {
+		return nil, errors.New("invalid native histogram schema")
+	}
+	if err := validateCount(sum, count, negativeBuckets, positiveBuckets, zeroBucket); err != nil {
+		return nil, err
+	}
+
+	NegativeSpan, NegativeDelta := makeBucketsFromMap(negativeBuckets)
+	PositiveSpan, PositiveDelta := makeBucketsFromMap(positiveBuckets)
+	ret := &constNativeHistogram{
+		desc: desc,
+		Histogram: dto.Histogram{
+			CreatedTimestamp: timestamppb.New(createdTimestamp),
+			Schema:           &schema,
+			ZeroThreshold:    &zeroThreshold,
+			SampleCount:      &count,
+			SampleSum:        &sum,
+
+			NegativeSpan:  NegativeSpan,
+			NegativeDelta: NegativeDelta,
+
+			PositiveSpan:  PositiveSpan,
+			PositiveDelta: PositiveDelta,
+
+			ZeroCount: proto.Uint64(zeroBucket),
+		},
+		labelPairs: MakeLabelPairs(desc, labelValues),
+	}
+	if *ret.ZeroThreshold == 0 && *ret.ZeroCount == 0 && len(ret.PositiveSpan) == 0 && len(ret.NegativeSpan) == 0 {
+		ret.PositiveSpan = []*dto.BucketSpan{{
+			Offset: proto.Int32(0),
+			Length: proto.Uint32(0),
+		}}
+	}
+	return ret, nil
+}
+
+// MustNewConstNativeHistogram is a version of NewConstNativeHistogram that panics where
+// NewConstNativeHistogram would have returned an error.
+func MustNewConstNativeHistogram(
+	desc *Desc,
+	count uint64,
+	sum float64,
+	positiveBuckets, negativeBuckets map[int]int64,
+	zeroBucket uint64,
+	nativeHistogramSchema int32,
+	nativeHistogramZeroThreshold float64,
+	createdTimestamp time.Time,
+	labelValues ...string,
+) Metric {
+	nativehistogram, err := NewConstNativeHistogram(desc,
+		count,
+		sum,
+		positiveBuckets,
+		negativeBuckets,
+		zeroBucket,
+		nativeHistogramSchema,
+		nativeHistogramZeroThreshold,
+		createdTimestamp,
+		labelValues...)
+	if err != nil {
+		panic(err)
+	}
+	return nativehistogram
+}
+
+func (h *constNativeHistogram) Desc() *Desc {
+	return h.desc
+}
+
+func (h *constNativeHistogram) Write(out *dto.Metric) error {
+	out.Histogram = &h.Histogram
+	out.Label = h.labelPairs
+	return nil
+}
+
+func makeBucketsFromMap(buckets map[int]int64) ([]*dto.BucketSpan, []int64) {
+	if len(buckets) == 0 {
+		return nil, nil
+	}
+	var ii []int
+	for k := range buckets {
+		ii = append(ii, k)
+	}
+	sort.Ints(ii)
+
+	var (
+		spans     []*dto.BucketSpan
+		deltas    []int64
+		prevCount int64
+		nextI     int
+	)
+
+	appendDelta := func(count int64) {
+		*spans[len(spans)-1].Length++
+		deltas = append(deltas, count-prevCount)
+		prevCount = count
+	}
+
+	for n, i := range ii {
+		count := buckets[i]
+		// Multiple spans with only small gaps in between are probably
+		// encoded more efficiently as one larger span with a few empty
+		// buckets. Needs some research to find the sweet spot. For now,
+		// we assume that gaps of one or two buckets should not create
+		// a new span.
+		iDelta := int32(i - nextI)
+		if n == 0 || iDelta > 2 {
+			// We have to create a new span, either because we are
+			// at the very beginning, or because we have found a gap
+			// of more than two buckets.
+			spans = append(spans, &dto.BucketSpan{
+				Offset: proto.Int32(iDelta),
+				Length: proto.Uint32(0),
+			})
+		} else {
+			// We have found a small gap (or no gap at all).
+			// Insert empty buckets as needed.
+			for j := int32(0); j < iDelta; j++ {
+				appendDelta(0)
+			}
+		}
+		appendDelta(count)
+		nextI = i + 1
+	}
+	return spans, deltas
+}

prometheus/histogram_test.go

@@ -25,11 +25,11 @@ import (
 	"testing/quick"
 	"time"
 
-	"github.com/prometheus/client_golang/prometheus/internal"
-
 	dto "github.com/prometheus/client_model/go"
 	"google.golang.org/protobuf/proto"
 	"google.golang.org/protobuf/types/known/timestamppb"
+
+	"github.com/prometheus/client_golang/prometheus/internal"
 )
 
 func benchmarkHistogramObserve(w int, b *testing.B) {
@@ -1455,3 +1455,632 @@ func compareNativeExemplarValues(t *testing.T, exps []*dto.Exemplar, values []fl
 		}
 	}
 }
+
+var resultFindBucket int
+
+func benchmarkFindBucket(b *testing.B, l int) {
+	h := &histogram{upperBounds: make([]float64, l)}
+	for i := range h.upperBounds {
+		h.upperBounds[i] = float64(i)
+	}
+	v := float64(l / 2)
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		resultFindBucket = h.findBucket(v)
+	}
+}
+
+func BenchmarkFindBucketShort(b *testing.B) {
+	benchmarkFindBucket(b, 20)
+}
+
+func BenchmarkFindBucketMid(b *testing.B) {
+	benchmarkFindBucket(b, 40)
+}
+
+func BenchmarkFindBucketLarge(b *testing.B) {
+	benchmarkFindBucket(b, 100)
+}
+
+func BenchmarkFindBucketHuge(b *testing.B) {
+	benchmarkFindBucket(b, 500)
+}
+
+func BenchmarkFindBucketInf(b *testing.B) {
+	h := &histogram{upperBounds: make([]float64, 500)}
+	for i := range h.upperBounds {
+		h.upperBounds[i] = float64(i)
+	}
+	v := 1000.5
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		resultFindBucket = h.findBucket(v)
+	}
+}
+
+func BenchmarkFindBucketLow(b *testing.B) {
+	h := &histogram{upperBounds: make([]float64, 500)}
+	for i := range h.upperBounds {
+		h.upperBounds[i] = float64(i)
+	}
+	v := -1.1
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		resultFindBucket = h.findBucket(v)
+	}
+}
+
+func TestFindBucket(t *testing.T) {
+	smallHistogram := &histogram{upperBounds: []float64{1, 2, 3, 4, 5}}
+	largeHistogram := &histogram{upperBounds: make([]float64, 50)}
+	for i := range largeHistogram.upperBounds {
+		largeHistogram.upperBounds[i] = float64(i)
+	}
+
+	tests := []struct {
+		h        *histogram
+		v        float64
+		expected int
+	}{
+		{smallHistogram, -1, 0},
+		{smallHistogram, 0.5, 0},
+		{smallHistogram, 2.5, 2},
+		{smallHistogram, 5.5, 5},
+		{largeHistogram, -1, 0},
+		{largeHistogram, 25.5, 26},
+		{largeHistogram, 49.5, 50},
+		{largeHistogram, 50.5, 50},
+		{largeHistogram, 5000.5, 50},
+	}
+
+	for _, tt := range tests {
+		result := tt.h.findBucket(tt.v)
+		if result != tt.expected {
+			t.Errorf("findBucket(%v) = %d; expected %d", tt.v, result, tt.expected)
+		}
+	}
+}
+
+func syncMapToMap(syncmap *sync.Map) (m map[int]int64) {
+	m = map[int]int64{}
+	syncmap.Range(func(key, value any) bool {
+		m[key.(int)] = *value.(*int64)
+		return true
+	})
+	return m
+}
+
+func TestConstNativeHistogram(t *testing.T) {
+	now := time.Now()
+
+	scenarios := []struct {
+		name             string
+		observations     []float64 // With simulated interval of 1m.
+		factor           float64
+		zeroThreshold    float64
+		maxBuckets       uint32
+		minResetDuration time.Duration
+		maxZeroThreshold float64
+		want             *dto.Histogram
+	}{
+		{
+			name:   "no observations",
+			factor: 1.1,
+			want: &dto.Histogram{
+				SampleCount:      proto.Uint64(0),
+				SampleSum:        proto.Float64(0),
+				Schema:           proto.Int32(3),
+				ZeroThreshold:    proto.Float64(2.938735877055719e-39),
+				ZeroCount:        proto.Uint64(0),
+				CreatedTimestamp: timestamppb.New(now),
+			},
+		},
+		{
+			name:          "no observations and zero threshold of zero resulting in no-op span",
+			factor:        1.1,
+			zeroThreshold: NativeHistogramZeroThresholdZero,
+			want: &dto.Histogram{
+				SampleCount:   proto.Uint64(0),
+				SampleSum:     proto.Float64(0),
+				Schema:        proto.Int32(3),
+				ZeroThreshold: proto.Float64(0),
+				ZeroCount:     proto.Uint64(0),
+				PositiveSpan: []*dto.BucketSpan{
+					{Offset: proto.Int32(0), Length: proto.Uint32(0)},
+				},
+				CreatedTimestamp: timestamppb.New(now),
+			},
+		},
+		{
+			name:         "factor 1.1 results in schema 3",
+			observations: []float64{0, 1, 2, 3},
+			factor:       1.1,
+			want: &dto.Histogram{
+				SampleCount:   proto.Uint64(4),
+				SampleSum:     proto.Float64(6),
+				Schema:        proto.Int32(3),
+				ZeroThreshold: proto.Float64(2.938735877055719e-39),
+				ZeroCount:     proto.Uint64(1),
+				PositiveSpan: []*dto.BucketSpan{
+					{Offset: proto.Int32(0), Length: proto.Uint32(1)},
+					{Offset: proto.Int32(7), Length: proto.Uint32(1)},
+					{Offset: proto.Int32(4), Length: proto.Uint32(1)},
+				},
+				PositiveDelta:    []int64{1, 0, 0},
+				CreatedTimestamp: timestamppb.New(now),
+			},
+		},
+		{
+			name:         "factor 1.2 results in schema 2",
+			observations: []float64{0, 1, 1.2, 1.4, 1.8, 2},
+			factor:       1.2,
+			want: &dto.Histogram{
+				SampleCount:   proto.Uint64(6),
+				SampleSum:     proto.Float64(7.4),
+				Schema:        proto.Int32(2),
+				ZeroThreshold: proto.Float64(2.938735877055719e-39),
+				ZeroCount:     proto.Uint64(1),
+				PositiveSpan: []*dto.BucketSpan{
+					{Offset: proto.Int32(0), Length: proto.Uint32(5)},
+				},
+				PositiveDelta:    []int64{1, -1, 2, -2, 2},
+				CreatedTimestamp: timestamppb.New(now),
+			},
+		},
+		{
+			name: "factor 4 results in schema -1",
+			observations: []float64{
+				0.0156251, 0.0625, // Bucket -2: (0.015625, 0.0625)
+				0.1, 0.25, // Bucket -1: (0.0625, 0.25]
+				0.5, 1, // Bucket 0: (0.25, 1]
+				1.5, 2, 3, 3.5, // Bucket 1: (1, 4]
+				5, 6, 7, // Bucket 2: (4, 16]
+				33.33, // Bucket 3: (16, 64]
+			},
+			factor: 4,
+			want: &dto.Histogram{
+				SampleCount:   proto.Uint64(14),
+				SampleSum:     proto.Float64(63.2581251),
+				Schema:        proto.Int32(-1),
+				ZeroThreshold: proto.Float64(2.938735877055719e-39),
+				ZeroCount:     proto.Uint64(0),
+				PositiveSpan: []*dto.BucketSpan{
+					{Offset: proto.Int32(-2), Length: proto.Uint32(6)},
+				},
+				PositiveDelta:    []int64{2, 0, 0, 2, -1, -2},
+				CreatedTimestamp: timestamppb.New(now),
+			},
+		},
+		{
+			name: "factor 17 results in schema -2",
+			observations: []float64{
+				0.0156251, 0.0625, // Bucket -1: (0.015625, 0.0625]
+				0.1, 0.25, 0.5, 1, // Bucket 0: (0.0625, 1]
+				1.5, 2, 3, 3.5, 5, 6, 7, // Bucket 1: (1, 16]
+				33.33, // Bucket 2: (16, 256]
+			},
+			factor: 17,
+			want: &dto.Histogram{
+				SampleCount:   proto.Uint64(14),
+				SampleSum:     proto.Float64(63.2581251),
+				Schema:        proto.Int32(-2),
+				ZeroThreshold: proto.Float64(2.938735877055719e-39),
+				ZeroCount:     proto.Uint64(0),
+				PositiveSpan: []*dto.BucketSpan{
+					{Offset: proto.Int32(-1), Length: proto.Uint32(4)},
+				},
+				PositiveDelta:    []int64{2, 2, 3, -6},
+				CreatedTimestamp: timestamppb.New(now),
+			},
+		},
+		{
+			name:         "negative buckets",
+			observations: []float64{0, -1, -1.2, -1.4, -1.8, -2},
+			factor:       1.2,
+			want: &dto.Histogram{
+				SampleCount:   proto.Uint64(6),
+				SampleSum:     proto.Float64(-7.4),
+				Schema:        proto.Int32(2),
+				ZeroThreshold: proto.Float64(2.938735877055719e-39),
+				ZeroCount:     proto.Uint64(1),
+				NegativeSpan: []*dto.BucketSpan{
+					{Offset: proto.Int32(0), Length: proto.Uint32(5)},
+				},
+				NegativeDelta:    []int64{1, -1, 2, -2, 2},
+				CreatedTimestamp: timestamppb.New(now),
+			},
+		},
+		{
+			name:         "negative and positive buckets",
+			observations: []float64{0, -1, -1.2, -1.4, -1.8, -2, 1, 1.2, 1.4, 1.8, 2},
+			factor:       1.2,
+			want: &dto.Histogram{
+				SampleCount:   proto.Uint64(11),
+				SampleSum:     proto.Float64(0),
+				Schema:        proto.Int32(2),
+				ZeroThreshold: proto.Float64(2.938735877055719e-39),
+				ZeroCount:     proto.Uint64(1),
+				NegativeSpan: []*dto.BucketSpan{
+					{Offset: proto.Int32(0), Length: proto.Uint32(5)},
+				},
+				NegativeDelta: []int64{1, -1, 2, -2, 2},
+				PositiveSpan: []*dto.BucketSpan{
+					{Offset: proto.Int32(0), Length: proto.Uint32(5)},
+				},
+				PositiveDelta:    []int64{1, -1, 2, -2, 2},
+				CreatedTimestamp: timestamppb.New(now),
+			},
+		},
+		{
+			name:          "wide zero bucket",
+			observations:  []float64{0, -1, -1.2, -1.4, -1.8, -2, 1, 1.2, 1.4, 1.8, 2},
+			factor:        1.2,
+			zeroThreshold: 1.4,
+			want: &dto.Histogram{
+				SampleCount:   proto.Uint64(11),
+				SampleSum:     proto.Float64(0),
+				Schema:        proto.Int32(2),
+				ZeroThreshold: proto.Float64(1.4),
+				ZeroCount:     proto.Uint64(7),
+				NegativeSpan: []*dto.BucketSpan{
+					{Offset: proto.Int32(4), Length: proto.Uint32(1)},
+				},
+				NegativeDelta: []int64{2},
+				PositiveSpan: []*dto.BucketSpan{
+					{Offset: proto.Int32(4), Length: proto.Uint32(1)},
+				},
+				PositiveDelta:    []int64{2},
+				CreatedTimestamp: timestamppb.New(now),
+			},
+		},
+		{
+			name:         "NaN observation",
+			observations: []float64{0, 1, 1.2, 1.4, 1.8, 2, math.NaN()},
+			factor:       1.2,
+			want: &dto.Histogram{
+				SampleCount:   proto.Uint64(7),
+				SampleSum:     proto.Float64(math.NaN()),
+				Schema:        proto.Int32(2),
+				ZeroThreshold: proto.Float64(2.938735877055719e-39),
+				ZeroCount:     proto.Uint64(1),
+				PositiveSpan: []*dto.BucketSpan{
+					{Offset: proto.Int32(0), Length: proto.Uint32(5)},
+				},
+				PositiveDelta:    []int64{1, -1, 2, -2, 2},
+				CreatedTimestamp: timestamppb.New(now),
+			},
+		},
+		{
+			name:         "+Inf observation",
+			observations: []float64{0, 1, 1.2, 1.4, 1.8, 2, math.Inf(+1)},
+			factor:       1.2,
+			want: &dto.Histogram{
+				SampleCount:   proto.Uint64(7),
+				SampleSum:     proto.Float64(math.Inf(+1)),
+				Schema:        proto.Int32(2),
+				ZeroThreshold: proto.Float64(2.938735877055719e-39),
+				ZeroCount:     proto.Uint64(1),
+				PositiveSpan: []*dto.BucketSpan{
+					{Offset: proto.Int32(0), Length: proto.Uint32(5)},
+					{Offset: proto.Int32(4092), Length: proto.Uint32(1)},
+				},
+				PositiveDelta:    []int64{1, -1, 2, -2, 2, -1},
+				CreatedTimestamp: timestamppb.New(now),
+			},
+		},
+		{
+			name:         "-Inf observation",
+			observations: []float64{0, 1, 1.2, 1.4, 1.8, 2, math.Inf(-1)},
+			factor:       1.2,
+			want: &dto.Histogram{
+				SampleCount:   proto.Uint64(7),
+				SampleSum:     proto.Float64(math.Inf(-1)),
+				Schema:        proto.Int32(2),
+				ZeroThreshold: proto.Float64(2.938735877055719e-39),
+				ZeroCount:     proto.Uint64(1),
+				NegativeSpan: []*dto.BucketSpan{
+					{Offset: proto.Int32(4097), Length: proto.Uint32(1)},
+				},
+				NegativeDelta: []int64{1},
+				PositiveSpan: []*dto.BucketSpan{
+					{Offset: proto.Int32(0), Length: proto.Uint32(5)},
+				},
+				PositiveDelta:    []int64{1, -1, 2, -2, 2},
+				CreatedTimestamp: timestamppb.New(now),
+			},
+		},
+		{
+			name:         "limited buckets but nothing triggered",
+			observations: []float64{0, 1, 1.2, 1.4, 1.8, 2},
+			factor:       1.2,
+			maxBuckets:   4,
+			want: &dto.Histogram{
+				SampleCount:   proto.Uint64(6),
+				SampleSum:     proto.Float64(7.4),
+				Schema:        proto.Int32(2),
+				ZeroThreshold: proto.Float64(2.938735877055719e-39),
+				ZeroCount:     proto.Uint64(1),
+				PositiveSpan: []*dto.BucketSpan{
+					{Offset: proto.Int32(0), Length: proto.Uint32(5)},
+				},
+				PositiveDelta:    []int64{1, -1, 2, -2, 2},
+				CreatedTimestamp: timestamppb.New(now),
+			},
+		},
+		{
+			name:         "buckets limited by halving resolution",
+			observations: []float64{0, 1, 1.1, 1.2, 1.4, 1.8, 2, 3},
+			factor:       1.2,
+			maxBuckets:   4,
+			want: &dto.Histogram{
+				SampleCount:   proto.Uint64(8),
+				SampleSum:     proto.Float64(11.5),
+				Schema:        proto.Int32(1),
+				ZeroThreshold: proto.Float64(2.938735877055719e-39),
+				ZeroCount:     proto.Uint64(1),
+				PositiveSpan: []*dto.BucketSpan{
+					{Offset: proto.Int32(0), Length: proto.Uint32(5)},
+				},
+				PositiveDelta:    []int64{1, 2, -1, -2, 1},
+				CreatedTimestamp: timestamppb.New(now),
+			},
+		},
+		{
+			name:             "buckets limited by widening the zero bucket",
+			observations:     []float64{0, 1, 1.1, 1.2, 1.4, 1.8, 2, 3},
+			factor:           1.2,
+			maxBuckets:       4,
+			maxZeroThreshold: 1.2,
+			want: &dto.Histogram{
+				SampleCount:   proto.Uint64(8),
+				SampleSum:     proto.Float64(11.5),
+				Schema:        proto.Int32(2),
+				ZeroThreshold: proto.Float64(1),
+				ZeroCount:     proto.Uint64(2),
+				PositiveSpan: []*dto.BucketSpan{
+					{Offset: proto.Int32(1), Length: proto.Uint32(7)},
+				},
+				PositiveDelta:    []int64{1, 1, -2, 2, -2, 0, 1},
+				CreatedTimestamp: timestamppb.New(now),
+			},
+		},
+		{
+			name:             "buckets limited by widening the zero bucket twice",
+			observations:     []float64{0, 1, 1.1, 1.2, 1.4, 1.8, 2, 3, 4},
+			factor:           1.2,
+			maxBuckets:       4,
+			maxZeroThreshold: 1.2,
+			want: &dto.Histogram{
+				SampleCount:   proto.Uint64(9),
+				SampleSum:     proto.Float64(15.5),
+				Schema:        proto.Int32(2),
+				ZeroThreshold: proto.Float64(1.189207115002721),
+				ZeroCount:     proto.Uint64(3),
+				PositiveSpan: []*dto.BucketSpan{
+					{Offset: proto.Int32(2), Length: proto.Uint32(7)},
+				},
+				PositiveDelta:    []int64{2, -2, 2, -2, 0, 1, 0},
+				CreatedTimestamp: timestamppb.New(now),
+			},
+		},
+		{
+			name:             "buckets limited by reset",
+			observations:     []float64{0, 1, 1.1, 1.2, 1.4, 1.8, 2, 3, 4},
+			factor:           1.2,
+			maxBuckets:       4,
+			maxZeroThreshold: 1.2,
+			minResetDuration: 5 * time.Minute,
+			want: &dto.Histogram{
+				SampleCount:   proto.Uint64(2),
+				SampleSum:     proto.Float64(7),
+				Schema:        proto.Int32(2),
+				ZeroThreshold: proto.Float64(2.938735877055719e-39),
+				ZeroCount:     proto.Uint64(0),
+				PositiveSpan: []*dto.BucketSpan{
+					{Offset: proto.Int32(7), Length: proto.Uint32(2)},
+				},
+				PositiveDelta:    []int64{1, 0},
+				CreatedTimestamp: timestamppb.New(now.Add(8 * time.Minute)), // We expect reset to happen after 8 observations.
+			},
+		},
+		{
+			name:         "limited buckets but nothing triggered, negative observations",
+			observations: []float64{0, -1, -1.2, -1.4, -1.8, -2},
+			factor:       1.2,
+			maxBuckets:   4,
+			want: &dto.Histogram{
+				SampleCount:   proto.Uint64(6),
+				SampleSum:     proto.Float64(-7.4),
+				Schema:        proto.Int32(2),
+				ZeroThreshold: proto.Float64(2.938735877055719e-39),
+				ZeroCount:     proto.Uint64(1),
+				NegativeSpan: []*dto.BucketSpan{
+					{Offset: proto.Int32(0), Length: proto.Uint32(5)},
+				},
+				NegativeDelta:    []int64{1, -1, 2, -2, 2},
+				CreatedTimestamp: timestamppb.New(now),
+			},
+		},
+		{
+			name:         "buckets limited by halving resolution, negative observations",
+			observations: []float64{0, -1, -1.1, -1.2, -1.4, -1.8, -2, -3},
+			factor:       1.2,
+			maxBuckets:   4,
+			want: &dto.Histogram{
+				SampleCount:   proto.Uint64(8),
+				SampleSum:     proto.Float64(-11.5),
+				Schema:        proto.Int32(1),
+				ZeroThreshold: proto.Float64(2.938735877055719e-39),
+				ZeroCount:     proto.Uint64(1),
+				NegativeSpan: []*dto.BucketSpan{
+					{Offset: proto.Int32(0), Length: proto.Uint32(5)},
+				},
+				NegativeDelta:    []int64{1, 2, -1, -2, 1},
+				CreatedTimestamp: timestamppb.New(now),
+			},
+		},
+		{
+			name:             "buckets limited by widening the zero bucket, negative observations",
+			observations:     []float64{0, -1, -1.1, -1.2, -1.4, -1.8, -2, -3},
+			factor:           1.2,
+			maxBuckets:       4,
+			maxZeroThreshold: 1.2,
+			want: &dto.Histogram{
+				SampleCount:   proto.Uint64(8),
+				SampleSum:     proto.Float64(-11.5),
+				Schema:        proto.Int32(2),
+				ZeroThreshold: proto.Float64(1),
+				ZeroCount:     proto.Uint64(2),
+				NegativeSpan: []*dto.BucketSpan{
+					{Offset: proto.Int32(1), Length: proto.Uint32(7)},
+				},
+				NegativeDelta:    []int64{1, 1, -2, 2, -2, 0, 1},
+				CreatedTimestamp: timestamppb.New(now),
+			},
+		},
+		{
+			name:             "buckets limited by widening the zero bucket twice, negative observations",
+			observations:     []float64{0, -1, -1.1, -1.2, -1.4, -1.8, -2, -3, -4},
+			factor:           1.2,
+			maxBuckets:       4,
+			maxZeroThreshold: 1.2,
+			want: &dto.Histogram{
+				SampleCount:   proto.Uint64(9),
+				SampleSum:     proto.Float64(-15.5),
+				Schema:        proto.Int32(2),
+				ZeroThreshold: proto.Float64(1.189207115002721),
+				ZeroCount:     proto.Uint64(3),
+				NegativeSpan: []*dto.BucketSpan{
+					{Offset: proto.Int32(2), Length: proto.Uint32(7)},
+				},
+				NegativeDelta:    []int64{2, -2, 2, -2, 0, 1, 0},
+				CreatedTimestamp: timestamppb.New(now),
+			},
+		},
+		{
+			name:             "buckets limited by reset, negative observations",
+			observations:     []float64{0, -1, -1.1, -1.2, -1.4, -1.8, -2, -3, -4},
+			factor:           1.2,
+			maxBuckets:       4,
+			maxZeroThreshold: 1.2,
+			minResetDuration: 5 * time.Minute,
+			want: &dto.Histogram{
+				SampleCount:   proto.Uint64(2),
+				SampleSum:     proto.Float64(-7),
+				Schema:        proto.Int32(2),
+				ZeroThreshold: proto.Float64(2.938735877055719e-39),
+				ZeroCount:     proto.Uint64(0),
+				NegativeSpan: []*dto.BucketSpan{
+					{Offset: proto.Int32(7), Length: proto.Uint32(2)},
+				},
+				NegativeDelta:    []int64{1, 0},
+				CreatedTimestamp: timestamppb.New(now.Add(8 * time.Minute)), // We expect reset to happen after 8 observations.
+			},
+		},
+		{
+			name:             "buckets limited by halving resolution, then reset",
+			observations:     []float64{0, 1, 1.1, 1.2, 1.4, 1.8, 2, 5, 5.1, 3, 4},
+			factor:           1.2,
+			maxBuckets:       4,
+			minResetDuration: 9 * time.Minute,
+			want: &dto.Histogram{
+				SampleCount:   proto.Uint64(3),
+				SampleSum:     proto.Float64(12.1),
+				Schema:        proto.Int32(2),
+				ZeroThreshold: proto.Float64(2.938735877055719e-39),
+				ZeroCount:     proto.Uint64(0),
+				PositiveSpan: []*dto.BucketSpan{
+					{Offset: proto.Int32(7), Length: proto.Uint32(4)},
+				},
+				PositiveDelta:    []int64{1, 0, -1, 1},
+				CreatedTimestamp: timestamppb.New(now.Add(9 * time.Minute)), // We expect reset to happen after 8 minutes.
+			},
+		},
+		{
+			name:             "buckets limited by widening the zero bucket, then reset",
+			observations:     []float64{0, 1, 1.1, 1.2, 1.4, 1.8, 2, 5, 5.1, 3, 4},
+			factor:           1.2,
+			maxBuckets:       4,
+			maxZeroThreshold: 1.2,
+			minResetDuration: 9 * time.Minute,
+			want: &dto.Histogram{
+				SampleCount:   proto.Uint64(3),
+				SampleSum:     proto.Float64(12.1),
+				Schema:        proto.Int32(2),
+				ZeroThreshold: proto.Float64(2.938735877055719e-39),
+				ZeroCount:     proto.Uint64(0),
+				PositiveSpan: []*dto.BucketSpan{
+					{Offset: proto.Int32(7), Length: proto.Uint32(4)},
+				},
+				PositiveDelta:    []int64{1, 0, -1, 1},
+				CreatedTimestamp: timestamppb.New(now.Add(9 * time.Minute)), // We expect reset to happen after 8 minutes.
+			},
+		},
+	}
+
+	for _, s := range scenarios {
+		t.Run(s.name, func(t *testing.T) {
+			var (
+				ts         = now
+				funcToCall func()
+				whenToCall time.Duration
+			)
+
+			his := NewHistogram(HistogramOpts{
+				Name:                            "name",
+				Help:                            "help",
+				NativeHistogramBucketFactor:     s.factor,
+				NativeHistogramZeroThreshold:    s.zeroThreshold,
+				NativeHistogramMaxBucketNumber:  s.maxBuckets,
+				NativeHistogramMinResetDuration: s.minResetDuration,
+				NativeHistogramMaxZeroThreshold: s.maxZeroThreshold,
+				now:                             func() time.Time { return ts },
+				afterFunc: func(d time.Duration, f func()) *time.Timer {
+					funcToCall = f
+					whenToCall = d
+					return nil
+				},
+			})
+
+			ts = ts.Add(time.Minute)
+			for _, o := range s.observations {
+				his.Observe(o)
+				ts = ts.Add(time.Minute)
+				whenToCall -= time.Minute
+				if funcToCall != nil && whenToCall <= 0 {
+					funcToCall()
+					funcToCall = nil
+				}
+			}
+			_his := his.(*histogram)
+			n := atomic.LoadUint64(&_his.countAndHotIdx)
+			hotIdx := n >> 63
+			cold := _his.counts[hotIdx]
+			consthist, err := NewConstNativeHistogram(_his.Desc(),
+				cold.count,
+				math.Float64frombits(cold.sumBits),
+				syncMapToMap(&cold.nativeHistogramBucketsPositive),
+				syncMapToMap(&cold.nativeHistogramBucketsNegative),
+				cold.nativeHistogramZeroBucket,
+				cold.nativeHistogramSchema,
+				math.Float64frombits(cold.nativeHistogramZeroThresholdBits),
+				_his.lastResetTime,
+			)
+			if err != nil {
+				t.Fatal("unexpected error writing metric", err)
+			}
+			m2 := &dto.Metric{}
+
+			if err := consthist.Write(m2); err != nil {
+				t.Fatal("unexpected error writing metric", err)
+			}
+			got := m2.Histogram
+			if !proto.Equal(s.want, got) {
+				t.Errorf("want histogram %q, got %q", s.want, got)
+			}
+		})
+	}
+}

prometheus/internal/difflib.go

@@ -22,6 +22,7 @@ import (
 	"bytes"
 	"fmt"
 	"io"
+	"strconv"
 	"strings"
 )
 
@@ -524,7 +525,7 @@ func formatRangeUnified(start, stop int) string {
 	beginning := start + 1 // lines start numbering with one
 	length := stop - start
 	if length == 1 {
-		return fmt.Sprintf("%d", beginning)
+		return strconv.Itoa(beginning)
 	}
 	if length == 0 {
 		beginning-- // empty ranges begin at line just before the range

prometheus/metric.go

@@ -108,15 +108,23 @@ func BuildFQName(namespace, subsystem, name string) string {
 	if name == "" {
 		return ""
 	}
-	switch {
-	case namespace != "" && subsystem != "":
-		return strings.Join([]string{namespace, subsystem, name}, "_")
-	case namespace != "":
-		return strings.Join([]string{namespace, name}, "_")
-	case subsystem != "":
-		return strings.Join([]string{subsystem, name}, "_")
+
+	sb := strings.Builder{}
+	sb.Grow(len(namespace) + len(subsystem) + len(name) + 2)
+
+	if namespace != "" {
+		sb.WriteString(namespace)
+		sb.WriteString("_")
 	}
-	return name
+
+	if subsystem != "" {
+		sb.WriteString(subsystem)
+		sb.WriteString("_")
+	}
+
+	sb.WriteString(name)
+
+	return sb.String()
 }
 
 type invalidMetric struct {

prometheus/process_collector_cgo_darwin.c

@@ -15,12 +15,16 @@
 
 #include <mach/mach_init.h>
 #include <mach/task.h>
-// Compiler warns that shared_memory_server.h is deprecated, use this instead.
-// But this doesn't define SHARED_DATA_REGION_SIZE or SHARED_TEXT_REGION_SIZE.
-//#include <mach/shared_region.h>
-#include <mach/shared_memory_server.h>
 #include <mach/mach_vm.h>
 
+// The compiler warns that mach/shared_memory_server.h is deprecated, and to use
+// mach/shared_region.h instead.  But that doesn't define
+// SHARED_DATA_REGION_SIZE or SHARED_TEXT_REGION_SIZE, so redefine them here and
+// avoid a warning message when running tests.
+#define GLOBAL_SHARED_TEXT_SEGMENT      0x90000000U
+#define SHARED_DATA_REGION_SIZE         0x10000000
+#define SHARED_TEXT_REGION_SIZE         0x10000000
+
 
 int get_memory_info(unsigned long long *rss, unsigned long long *vsize)
 {

prometheus/process_collector_cgo_darwin.go

@@ -22,9 +22,7 @@ import "C"
 import "fmt"
 
 func getMemory() (*memoryInfo, error) {
-	var (
-		rss, vsize C.ulonglong
-	)
+	var rss, vsize C.ulonglong
 
 	if err := C.get_memory_info(&rss, &vsize); err != 0 {
 		return nil, fmt.Errorf("task_info() failed with 0x%x", int(err))

prometheus/process_collector_darwin.go

@@ -25,7 +25,7 @@ import (
 
 // notImplementedErr is returned by stub functions that replace cgo functions, when cgo
 // isn't available.
-var notImplementedErr = fmt.Errorf("not implemented")
+var notImplementedErr = errors.New("not implemented")
 
 type memoryInfo struct {
 	vsize uint64 // Virtual memory size in bytes

prometheus/promhttp/http_test.go

@@ -98,7 +98,7 @@ func readCompressedBody(r io.Reader, comp Compression) (string, error) {
 		got, err := io.ReadAll(reader)
 		return string(got), err
 	}
-	return "", fmt.Errorf("Unsupported compression")
+	return "", errors.New("Unsupported compression")
 }
 
 func TestHandlerErrorHandling(t *testing.T) {
@@ -131,7 +131,7 @@ func TestHandlerErrorHandling(t *testing.T) {
 	logger := log.New(logBuf, "", 0)
 
 	writer := httptest.NewRecorder()
-	request, _ := http.NewRequest("GET", "/", nil)
+	request, _ := http.NewRequest(http.MethodGet, "/", nil)
 	request.Header.Add("Accept", "test/plain")
 
 	mReg := &mockTransactionGatherer{g: reg}
@@ -252,7 +252,7 @@ func TestInstrumentMetricHandler(t *testing.T) {
 	// Do it again to test idempotency.
 	InstrumentMetricHandler(reg, HandlerForTransactional(mReg, HandlerOpts{}))
 	writer := httptest.NewRecorder()
-	request, _ := http.NewRequest("GET", "/", nil)
+	request, _ := http.NewRequest(http.MethodGet, "/", nil)
 	request.Header.Add(acceptHeader, acceptTextPlain)
 
 	handler.ServeHTTP(writer, request)
@@ -311,7 +311,7 @@ func TestHandlerMaxRequestsInFlight(t *testing.T) {
 	w1 := httptest.NewRecorder()
 	w2 := httptest.NewRecorder()
 	w3 := httptest.NewRecorder()
-	request, _ := http.NewRequest("GET", "/", nil)
+	request, _ := http.NewRequest(http.MethodGet, "/", nil)
 	request.Header.Add(acceptHeader, acceptTextPlain)
 
 	c := blockingCollector{Block: make(chan struct{}), CollectStarted: make(chan struct{}, 1)}
@@ -348,7 +348,7 @@ func TestHandlerTimeout(t *testing.T) {
 	handler := HandlerFor(reg, HandlerOpts{Timeout: time.Millisecond})
 	w := httptest.NewRecorder()
 
-	request, _ := http.NewRequest("GET", "/", nil)
+	request, _ := http.NewRequest(http.MethodGet, "/", nil)
 	request.Header.Add("Accept", "test/plain")
 
 	c := blockingCollector{Block: make(chan struct{}), CollectStarted: make(chan struct{}, 1)}
@@ -372,7 +372,7 @@ func TestInstrumentMetricHandlerWithCompression(t *testing.T) {
 	handler := InstrumentMetricHandler(reg, HandlerForTransactional(mReg, HandlerOpts{DisableCompression: false}))
 	compression := Zstd
 	writer := httptest.NewRecorder()
-	request, _ := http.NewRequest("GET", "/", nil)
+	request, _ := http.NewRequest(http.MethodGet, "/", nil)
 	request.Header.Add(acceptHeader, acceptTextPlain)
 	request.Header.Add(acceptEncodingHeader, string(compression))
 
@@ -533,7 +533,7 @@ func TestNegotiateEncodingWriter(t *testing.T) {
 	}
 
 	for _, test := range testCases {
-		request, _ := http.NewRequest("GET", "/", nil)
+		request, _ := http.NewRequest(http.MethodGet, "/", nil)
 		request.Header.Add(acceptEncodingHeader, test.acceptEncoding)
 		rr := httptest.NewRecorder()
 		_, encodingHeader, _, err := negotiateEncodingWriter(request, rr, test.offeredCompressions)
@@ -631,7 +631,7 @@ func BenchmarkCompression(b *testing.B) {
 			b.Run(benchmark.name+"_"+size.name, func(b *testing.B) {
 				for i := 0; i < b.N; i++ {
 					writer := httptest.NewRecorder()
-					request, _ := http.NewRequest("GET", "/", nil)
+					request, _ := http.NewRequest(http.MethodGet, "/", nil)
 					request.Header.Add(acceptEncodingHeader, benchmark.compressionType)
 					handler.ServeHTTP(writer, request)
 				}

prometheus/promhttp/instrument_client_test.go

@@ -223,7 +223,7 @@ func TestClientMiddlewareAPI_WithRequestContext(t *testing.T) {
 	}))
 	defer backend.Close()
 
-	req, err := http.NewRequest("GET", backend.URL, nil)
+	req, err := http.NewRequest(http.MethodGet, backend.URL, nil)
 	if err != nil {
 		t.Fatalf("%v", err)
 	}
@@ -276,7 +276,7 @@ func TestClientMiddlewareAPIWithRequestContextTimeout(t *testing.T) {
 	}))
 	defer backend.Close()
 
-	req, err := http.NewRequest("GET", backend.URL, nil)
+	req, err := http.NewRequest(http.MethodGet, backend.URL, nil)
 	if err != nil {
 		t.Fatalf("%v", err)
 	}

prometheus/promhttp/instrument_server_test.go

@@ -418,7 +418,7 @@ func TestMiddlewareAPI(t *testing.T) {
 		_, _ = w.Write([]byte("OK"))
 	})
 
-	r, _ := http.NewRequest("GET", "www.example.com", nil)
+	r, _ := http.NewRequest(http.MethodGet, "www.example.com", nil)
 	w := httptest.NewRecorder()
 	chain.ServeHTTP(w, r)
 
@@ -432,7 +432,7 @@ func TestMiddlewareAPI_WithExemplars(t *testing.T) {
 		_, _ = w.Write([]byte("OK"))
 	}, WithExemplarFromContext(func(_ context.Context) prometheus.Labels { return exemplar }))
 
-	r, _ := http.NewRequest("GET", "www.example.com", nil)
+	r, _ := http.NewRequest(http.MethodGet, "www.example.com", nil)
 	w := httptest.NewRecorder()
 	chain.ServeHTTP(w, r)
 

prometheus/registry_test.go

@@ -27,6 +27,7 @@ import (
 	"net/http"
 	"net/http/httptest"
 	"os"
+	"strconv"
 	"sync"
 	"testing"
 	"time"
@@ -713,7 +714,7 @@ collected metric "broken_metric" { label:<name:"foo" value:"bar" > label:<name:"
 		}
 		writer := httptest.NewRecorder()
 		handler := promhttp.HandlerFor(gatherer, promhttp.HandlerOpts{})
-		request, _ := http.NewRequest("GET", "/", nil)
+		request, _ := http.NewRequest(http.MethodGet, "/", nil)
 		for key, value := range scenario.headers {
 			request.Header.Add(key, value)
 		}
@@ -1282,7 +1283,7 @@ func ExampleRegistry_grouping() {
 				ConstLabels: prometheus.Labels{
 					// Generate a label unique to this worker so its metric doesn't
 					// collide with the metrics from other workers.
-					"worker_id": fmt.Sprintf("%d", workerID),
+					"worker_id": strconv.Itoa(workerID),
 				},
 			})
 			workerReg.MustRegister(workTime)

prometheus/summary.go

@@ -243,6 +243,7 @@ func newSummary(desc *Desc, opts SummaryOpts, labelValues ...string) Summary {
 
 	s := &summary{
 		desc: desc,
+		now:  opts.now,
 
 		objectives:       opts.Objectives,
 		sortedObjectives: make([]float64, 0, len(opts.Objectives)),
@@ -280,6 +281,8 @@ type summary struct {
 
 	desc *Desc
 
+	now func() time.Time
+
 	objectives       map[float64]float64
 	sortedObjectives []float64
 
@@ -307,7 +310,7 @@ func (s *summary) Observe(v float64) {
 	s.bufMtx.Lock()
 	defer s.bufMtx.Unlock()
 
-	now := time.Now()
+	now := s.now()
 	if now.After(s.hotBufExpTime) {
 		s.asyncFlush(now)
 	}
@@ -326,7 +329,7 @@ func (s *summary) Write(out *dto.Metric) error {
 	s.bufMtx.Lock()
 	s.mtx.Lock()
 	// Swap bufs even if hotBuf is empty to set new hotBufExpTime.
-	s.swapBufs(time.Now())
+	s.swapBufs(s.now())
 	s.bufMtx.Unlock()
 
 	s.flushColdBuf()
@@ -468,13 +471,9 @@ func (s *noObjectivesSummary) Observe(v float64) {
 	n := atomic.AddUint64(&s.countAndHotIdx, 1)
 	hotCounts := s.counts[n>>63]
 
-	for {
-		oldBits := atomic.LoadUint64(&hotCounts.sumBits)
-		newBits := math.Float64bits(math.Float64frombits(oldBits) + v)
-		if atomic.CompareAndSwapUint64(&hotCounts.sumBits, oldBits, newBits) {
-			break
-		}
-	}
+	atomicUpdateFloat(&hotCounts.sumBits, func(oldVal float64) float64 {
+		return oldVal + v
+	})
 	// Increment count last as we take it as a signal that the observation
 	// is complete.
 	atomic.AddUint64(&hotCounts.count, 1)
@@ -516,14 +515,13 @@ func (s *noObjectivesSummary) Write(out *dto.Metric) error {
 	// Finally add all the cold counts to the new hot counts and reset the cold counts.
 	atomic.AddUint64(&hotCounts.count, count)
 	atomic.StoreUint64(&coldCounts.count, 0)
-	for {
-		oldBits := atomic.LoadUint64(&hotCounts.sumBits)
-		newBits := math.Float64bits(math.Float64frombits(oldBits) + sum.GetSampleSum())
-		if atomic.CompareAndSwapUint64(&hotCounts.sumBits, oldBits, newBits) {
+
+	// Use atomicUpdateFloat to update hotCounts.sumBits atomically.
+	atomicUpdateFloat(&hotCounts.sumBits, func(oldVal float64) float64 {
+		return oldVal + sum.GetSampleSum()
+	})
 	atomic.StoreUint64(&coldCounts.sumBits, 0)
-			break
-		}
-	}
+
 	return nil
 }
 

prometheus/summary_test.go

@@ -371,10 +371,7 @@ func TestSummaryVecConcurrency(t *testing.T) {
 }
 
 func TestSummaryDecay(t *testing.T) {
-	if testing.Short() {
-		t.Skip("Skipping test in short mode.")
-		// More because it depends on timing than because it is particularly long...
-	}
+	now := time.Now()
 
 	sum := NewSummary(SummaryOpts{
 		Name:       "test_summary",
@@ -382,28 +379,28 @@ func TestSummaryDecay(t *testing.T) {
 		MaxAge:     100 * time.Millisecond,
 		Objectives: map[float64]float64{0.1: 0.001},
 		AgeBuckets: 10,
+		now: func() time.Time {
+			return now
+		},
 	})
 
 	m := &dto.Metric{}
-	i := 0
-	tick := time.NewTicker(time.Millisecond)
-	for range tick.C {
-		i++
+	for i := 1; i <= 1000; i++ {
+		now = now.Add(time.Millisecond)
 		sum.Observe(float64(i))
 		if i%10 == 0 {
 			sum.Write(m)
-			if got, want := *m.Summary.Quantile[0].Value, math.Max(float64(i)/10, float64(i-90)); math.Abs(got-want) > 20 {
+			got := *m.Summary.Quantile[0].Value
+			want := math.Max(float64(i)/10, float64(i-90))
+			if math.Abs(got-want) > 20 {
 				t.Errorf("%d. got %f, want %f", i, got, want)
 			}
 			m.Reset()
 		}
-		if i >= 1000 {
-			break
 	}
-	}
-	tick.Stop()
-	// Wait for MaxAge without observations and make sure quantiles are NaN.
-	time.Sleep(100 * time.Millisecond)
+
+	// Simulate waiting for MaxAge without observations
+	now = now.Add(100 * time.Millisecond)
 	sum.Write(m)
 	if got := *m.Summary.Quantile[0].Value; !math.IsNaN(got) {
 		t.Errorf("got %f, want NaN after expiration", got)

prometheus/testutil/promlint/promlint_test.go

@@ -14,6 +14,7 @@
 package promlint_test
 
 import (
+	"errors"
 	"fmt"
 	"reflect"
 	"strings"
@@ -733,7 +734,7 @@ request_duration_seconds{httpService="foo"} 10
 func TestLintUnitAbbreviations(t *testing.T) {
 	genTest := func(n string) test {
 		return test{
-			name: fmt.Sprintf("%s with abbreviated unit", n),
+			name: n + " with abbreviated unit",
 			in: fmt.Sprintf(`
 # HELP %s Test metric.
 # TYPE %s gauge
@@ -820,7 +821,7 @@ mc_something_total 10
 
 	prefixValidation := func(mf *dto.MetricFamily) []error {
 		if !strings.HasPrefix(mf.GetName(), "memcached_") {
-			return []error{fmt.Errorf("expected metric name to start with 'memcached_'")}
+			return []error{errors.New("expected metric name to start with 'memcached_'")}
 		}
 		return nil
 	}

prometheus/testutil/promlint/validations/duplicate_validations.go

@@ -14,7 +14,7 @@
 package validations
 
 import (
-	"fmt"
+	"errors"
 	"reflect"
 
 	dto "github.com/prometheus/client_model/go"
@@ -27,7 +27,7 @@ func LintDuplicateMetric(mf *dto.MetricFamily) []error {
 	for i, m := range mf.Metric {
 		for _, k := range mf.Metric[i+1:] {
 			if reflect.DeepEqual(m.Label, k.Label) {
-				problems = append(problems, fmt.Errorf("metric not unique"))
+				problems = append(problems, errors.New("metric not unique"))
 				break
 			}
 		}

prometheus/testutil/testutil.go

@@ -160,6 +160,9 @@ func GatherAndCount(g prometheus.Gatherer, metricNames ...string) (int, error) {
 // ScrapeAndCompare calls a remote exporter's endpoint which is expected to return some metrics in
 // plain text format. Then it compares it with the results that the `expected` would return.
 // If the `metricNames` is not empty it would filter the comparison only to the given metric names.
+//
+// NOTE: Be mindful of accidental discrepancies between expected and metricNames; metricNames filter
+// both expected and scraped metrics. See https://github.com/prometheus/client_golang/issues/1351.
 func ScrapeAndCompare(url string, expected io.Reader, metricNames ...string) error {
 	resp, err := http.Get(url)
 	if err != nil {
@@ -187,6 +190,9 @@ func ScrapeAndCompare(url string, expected io.Reader, metricNames ...string) err
 
 // CollectAndCompare collects the metrics identified by `metricNames` and compares them in the Prometheus text
 // exposition format to the data read from expected.
+//
+// NOTE: Be mindful of accidental discrepancies between expected and metricNames; metricNames filter
+// both expected and collected metrics. See https://github.com/prometheus/client_golang/issues/1351.
 func CollectAndCompare(c prometheus.Collector, expected io.Reader, metricNames ...string) error {
 	reg := prometheus.NewPedanticRegistry()
 	if err := reg.Register(c); err != nil {
@@ -199,6 +205,9 @@ func CollectAndCompare(c prometheus.Collector, expected io.Reader, metricNames .
 // it to an expected output read from the provided Reader in the Prometheus text
 // exposition format. If any metricNames are provided, only metrics with those
 // names are compared.
+//
+// NOTE: Be mindful of accidental discrepancies between expected and metricNames; metricNames filter
+// both expected and gathered metrics. See https://github.com/prometheus/client_golang/issues/1351.
 func GatherAndCompare(g prometheus.Gatherer, expected io.Reader, metricNames ...string) error {
 	return TransactionalGatherAndCompare(prometheus.ToTransactionalGatherer(g), expected, metricNames...)
 }
@@ -207,6 +216,9 @@ func GatherAndCompare(g prometheus.Gatherer, expected io.Reader, metricNames ...
 // it to an expected output read from the provided Reader in the Prometheus text
 // exposition format. If any metricNames are provided, only metrics with those
 // names are compared.
+//
+// NOTE: Be mindful of accidental discrepancies between expected and metricNames; metricNames filter
+// both expected and gathered metrics. See https://github.com/prometheus/client_golang/issues/1351.
 func TransactionalGatherAndCompare(g prometheus.TransactionalGatherer, expected io.Reader, metricNames ...string) error {
 	got, done, err := g.Gather()
 	defer done()
@@ -279,15 +291,6 @@ func compareMetricFamilies(got, expected []*dto.MetricFamily, metricNames ...str
 	if metricNames != nil {
 		got = filterMetrics(got, metricNames)
 		expected = filterMetrics(expected, metricNames)
-		if len(metricNames) > len(got) {
-			var missingMetricNames []string
-			for _, name := range metricNames {
-				if ok := hasMetricByName(got, name); !ok {
-					missingMetricNames = append(missingMetricNames, name)
-				}
-			}
-			return fmt.Errorf("expected metric name(s) not found: %v", missingMetricNames)
-		}
 	}
 
 	return compare(got, expected)
@@ -329,12 +332,3 @@ func filterMetrics(metrics []*dto.MetricFamily, names []string) []*dto.MetricFam
 	}
 	return filtered
 }
-
-func hasMetricByName(metrics []*dto.MetricFamily, name string) bool {
-	for _, mf := range metrics {
-		if mf.GetName() == name {
-			return true
-		}
-	}
-	return false
-}

prometheus/testutil/testutil_test.go

@@ -328,94 +328,51 @@ func TestMetricNotFound(t *testing.T) {
 }
 
 func TestScrapeAndCompare(t *testing.T) {
-	scenarios := map[string]struct {
-		want        string
-		metricNames []string
-		// expectedErr if empty, means no fail is expected for the comparison.
-		expectedErr string
-	}{
-		"empty metric Names": {
-			want: `
+	const expected = `
 		# HELP some_total A value that represents a counter.
 		# TYPE some_total counter
 
 		some_total{ label1 = "value1" } 1
-	`,
-			metricNames: []string{},
-		},
-		"one metric": {
-			want: `
-		# HELP some_total A value that represents a counter.
-		# TYPE some_total counter
+	`
 
-		some_total{ label1 = "value1" } 1
-	`,
-			metricNames: []string{"some_total"},
-		},
-		"multiple expected": {
-			want: `
-		# HELP some_total A value that represents a counter.
-		# TYPE some_total counter
-
-		some_total{ label1 = "value1" } 1
-
-		# HELP some_total2 A value that represents a counter.
-		# TYPE some_total2 counter
-
-		some_total2{ label2 = "value2" } 1
-	`,
-			metricNames: []string{"some_total2"},
-		},
-		"expected metric name is not scraped": {
-			want: `
-		# HELP some_total A value that represents a counter.
-		# TYPE some_total counter
-
-		some_total{ label1 = "value1" } 1
-
-		# HELP some_total2 A value that represents a counter.
-		# TYPE some_total2 counter
-
-		some_total2{ label2 = "value2" } 1
-	`,
-			metricNames: []string{"some_total3"},
-			expectedErr: "expected metric name(s) not found: [some_total3]",
-		},
-		"one of multiple expected metric names is not scraped": {
-			want: `
-		# HELP some_total A value that represents a counter.
-		# TYPE some_total counter
-
-		some_total{ label1 = "value1" } 1
-
-		# HELP some_total2 A value that represents a counter.
-		# TYPE some_total2 counter
-
-		some_total2{ label2 = "value2" } 1
-	`,
-			metricNames: []string{"some_total1", "some_total3"},
-			expectedErr: "expected metric name(s) not found: [some_total1 some_total3]",
-		},
-	}
-	for name, scenario := range scenarios {
-		t.Run(name, func(t *testing.T) {
-			expectedReader := strings.NewReader(scenario.want)
+	expectedReader := strings.NewReader(expected)
 
 	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-				fmt.Fprintln(w, scenario.want)
+		fmt.Fprintln(w, expected)
 	}))
 	defer ts.Close()
-			if err := ScrapeAndCompare(ts.URL, expectedReader, scenario.metricNames...); err != nil {
-				if scenario.expectedErr == "" || err.Error() != scenario.expectedErr {
-					t.Errorf("unexpected error happened: %s", err)
+
+	if err := ScrapeAndCompare(ts.URL, expectedReader, "some_total"); err != nil {
+		t.Errorf("unexpected scraping result:\n%s", err)
 	}
-			} else if scenario.expectedErr != "" {
-				t.Errorf("expected an error but got nil")
-			}
-		})
 }
 
-	t.Run("fetching fail", func(t *testing.T) {
+func TestScrapeAndCompareWithMultipleExpected(t *testing.T) {
+	const expected = `
+		# HELP some_total A value that represents a counter.
+		# TYPE some_total counter
+
+		some_total{ label1 = "value1" } 1
+
+		# HELP some_total2 A value that represents a counter.
+		# TYPE some_total2 counter
+
+		some_total2{ label2 = "value2" } 1
+	`
+
+	expectedReader := strings.NewReader(expected)
+
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		fmt.Fprintln(w, expected)
+	}))
+	defer ts.Close()
+
+	if err := ScrapeAndCompare(ts.URL, expectedReader, "some_total2"); err != nil {
+		t.Errorf("unexpected scraping result:\n%s", err)
+	}
+}
+
+func TestScrapeAndCompareFetchingFail(t *testing.T) {
 	err := ScrapeAndCompare("some_url", strings.NewReader("some expectation"), "some_total")
 	if err == nil {
 		t.Errorf("expected an error but got nil")
@@ -423,9 +380,9 @@ func TestScrapeAndCompare(t *testing.T) {
 	if !strings.HasPrefix(err.Error(), "scraping metrics failed") {
 		t.Errorf("unexpected error happened: %s", err)
 	}
-	})
+}
 
-	t.Run("bad status code", func(t *testing.T) {
+func TestScrapeAndCompareBadStatusCode(t *testing.T) {
 	const expected = `
 		# HELP some_total A value that represents a counter.
 		# TYPE some_total counter
@@ -448,7 +405,6 @@ func TestScrapeAndCompare(t *testing.T) {
 	if !strings.HasPrefix(err.Error(), "the scraping target returned a status code other than 200") {
 		t.Errorf("unexpected error happened: %s", err)
 	}
-	})
 }
 
 func TestCollectAndCount(t *testing.T) {

prometheus/value_test.go

@@ -14,7 +14,6 @@
 package prometheus
 
 import (
-	"fmt"
 	"testing"
 	"time"
 
@@ -51,7 +50,7 @@ func TestNewConstMetricInvalidLabelValues(t *testing.T) {
 
 		expectPanic(t, func() {
 			MustNewConstMetric(metricDesc, CounterValue, 0.3, "\xFF")
-		}, fmt.Sprintf("WithLabelValues: expected panic because: %s", test.desc))
+		}, "WithLabelValues: expected panic because: "+test.desc)
 
 		if _, err := NewConstMetric(metricDesc, CounterValue, 0.3, "\xFF"); err == nil {
 			t.Errorf("NewConstMetric: expected error because: %s", test.desc)

prometheus/vec_test.go

@@ -16,6 +16,7 @@ package prometheus
 import (
 	"fmt"
 	"reflect"
+	"strconv"
 	"testing"
 
 	dto "github.com/prometheus/client_model/go"
@@ -291,7 +292,7 @@ func testMetricVec(t *testing.T, vec *GaugeVec) {
 	expected := map[[2]string]int{}
 
 	for i := 0; i < 1000; i++ {
-		pair[0], pair[1] = fmt.Sprint(i%4), fmt.Sprint(i%5) // Varying combinations multiples.
+		pair[0], pair[1] = strconv.Itoa(i%4), strconv.Itoa(i%5) // Varying combinations multiples.
 		expected[pair]++
 		vec.WithLabelValues(pair[0], pair[1]).Inc()
 
@@ -363,7 +364,7 @@ func testConstrainedMetricVec(t *testing.T, vec *GaugeVec, constrain func(string
 	expected := map[[2]string]int{}
 
 	for i := 0; i < 1000; i++ {
-		pair[0], pair[1] = fmt.Sprint(i%4), fmt.Sprint(i%5) // Varying combinations multiples.
+		pair[0], pair[1] = strconv.Itoa(i%4), strconv.Itoa(i%5) // Varying combinations multiples.
 		expected[[2]string{pair[0], constrain(pair[1])}]++
 		vec.WithLabelValues(pair[0], pair[1]).Inc()