prometheus/scrape/scrape_test.go

// Copyright 2016 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 scrape

import (
	"bytes"
	"compress/gzip"
	"context"
	"encoding/binary"
	"errors"
	"fmt"
	"io"
	"math"
	"net/http"
	"net/http/httptest"
	"net/url"
	"strconv"
	"strings"
	"sync"
	"testing"
	"text/template"
	"time"

	"github.com/gogo/protobuf/proto"
	"github.com/google/go-cmp/cmp"
	"github.com/grafana/regexp"
	"github.com/prometheus/client_golang/prometheus"
	prom_testutil "github.com/prometheus/client_golang/prometheus/testutil"
	dto "github.com/prometheus/client_model/go"
	config_util "github.com/prometheus/common/config"
	"github.com/prometheus/common/expfmt"
	"github.com/prometheus/common/model"
	"github.com/prometheus/common/promslog"
	"github.com/stretchr/testify/require"

	"github.com/prometheus/prometheus/config"
	"github.com/prometheus/prometheus/discovery"
	"github.com/prometheus/prometheus/discovery/targetgroup"
	"github.com/prometheus/prometheus/model/exemplar"
	"github.com/prometheus/prometheus/model/histogram"
	"github.com/prometheus/prometheus/model/labels"
	"github.com/prometheus/prometheus/model/relabel"
	"github.com/prometheus/prometheus/model/textparse"
	"github.com/prometheus/prometheus/model/timestamp"
	"github.com/prometheus/prometheus/model/value"
	"github.com/prometheus/prometheus/storage"
	"github.com/prometheus/prometheus/tsdb/chunkenc"
	"github.com/prometheus/prometheus/util/logging"
	"github.com/prometheus/prometheus/util/pool"
	"github.com/prometheus/prometheus/util/teststorage"
	"github.com/prometheus/prometheus/util/testutil"
)

func TestMain(m *testing.M) {
	testutil.TolerantVerifyLeak(m)
}

func newTestRegistryAndScrapeMetrics(t testing.TB) (*prometheus.Registry, *scrapeMetrics) {
	reg := prometheus.NewRegistry()
	metrics, err := newScrapeMetrics(reg)
	require.NoError(t, err)
	return reg, metrics
}

func newTestScrapeMetrics(t testing.TB) *scrapeMetrics {
	_, metrics := newTestRegistryAndScrapeMetrics(t)
	return metrics
}

func TestNewScrapePool(t *testing.T) {
	var (
		app   = &nopAppendable{}
		cfg   = &config.ScrapeConfig{}
		sp, _ = newScrapePool(cfg, app, 0, nil, nil, &Options{}, newTestScrapeMetrics(t))
	)

	a, ok := sp.appendable.(*nopAppendable)
	require.True(t, ok, "Failure to append.")
	require.Equal(t, app, a, "Wrong sample appender.")
	require.Equal(t, cfg, sp.config, "Wrong scrape config.")
	require.NotNil(t, sp.newLoop, "newLoop function not initialized.")
}

func TestStorageHandlesOutOfOrderTimestamps(t *testing.T) {
	// Test with default OutOfOrderTimeWindow (0)
	t.Run("Out-Of-Order Sample Disabled", func(t *testing.T) {
		s := teststorage.New(t)
		defer s.Close()

		runScrapeLoopTest(t, s, false)
	})

	// Test with specific OutOfOrderTimeWindow (600000)
	t.Run("Out-Of-Order Sample Enabled", func(t *testing.T) {
		s := teststorage.New(t, 600000)
		defer s.Close()

		runScrapeLoopTest(t, s, true)
	})
}

func runScrapeLoopTest(t *testing.T, s *teststorage.TestStorage, expectOutOfOrder bool) {
	// Create an appender for adding samples to the storage.
	app := s.Appender(context.Background())
	capp := &collectResultAppender{next: app}
	sl := newBasicScrapeLoop(t, context.Background(), nil, func(ctx context.Context) storage.Appender { return capp }, 0)

	// Current time for generating timestamps.
	now := time.Now()

	// Calculate timestamps for the samples based on the current time.
	now = now.Truncate(time.Minute) // round down the now timestamp to the nearest minute
	timestampInorder1 := now
	timestampOutOfOrder := now.Add(-5 * time.Minute)
	timestampInorder2 := now.Add(5 * time.Minute)

	slApp := sl.appender(context.Background())
	_, _, _, err := sl.append(slApp, []byte(`metric_a{a="1",b="1"} 1`), "text/plain", timestampInorder1)
	require.NoError(t, err)

	_, _, _, err = sl.append(slApp, []byte(`metric_a{a="1",b="1"} 2`), "text/plain", timestampOutOfOrder)
	require.NoError(t, err)

	_, _, _, err = sl.append(slApp, []byte(`metric_a{a="1",b="1"} 3`), "text/plain", timestampInorder2)
	require.NoError(t, err)

	require.NoError(t, slApp.Commit())

	// Query the samples back from the storage.
	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()
	q, err := s.Querier(time.Time{}.UnixNano(), time.Now().UnixNano())
	require.NoError(t, err)
	defer q.Close()

	// Use a matcher to filter the metric name.
	series := q.Select(ctx, false, nil, labels.MustNewMatcher(labels.MatchRegexp, "__name__", "metric_a"))

	var results []floatSample
	for series.Next() {
		it := series.At().Iterator(nil)
		for it.Next() == chunkenc.ValFloat {
			t, v := it.At()
			results = append(results, floatSample{
				metric: series.At().Labels(),
				t:      t,
				f:      v,
			})
		}
		require.NoError(t, it.Err())
	}
	require.NoError(t, series.Err())

	// Define the expected results
	want := []floatSample{
		{
			metric: labels.FromStrings("__name__", "metric_a", "a", "1", "b", "1"),
			t:      timestamp.FromTime(timestampInorder1),
			f:      1,
		},
		{
			metric: labels.FromStrings("__name__", "metric_a", "a", "1", "b", "1"),
			t:      timestamp.FromTime(timestampInorder2),
			f:      3,
		},
	}

	if expectOutOfOrder {
		require.NotEqual(t, want, results, "Expected results to include out-of-order sample:\n%s", results)
	} else {
		require.Equal(t, want, results, "Appended samples not as expected:\n%s", results)
	}
}

func TestDroppedTargetsList(t *testing.T) {
	var (
		app = &nopAppendable{}
		cfg = &config.ScrapeConfig{
			JobName:        "dropMe",
			ScrapeInterval: model.Duration(1),
			RelabelConfigs: []*relabel.Config{
				{
					Action:       relabel.Drop,
					Regex:        relabel.MustNewRegexp("dropMe"),
					SourceLabels: model.LabelNames{"job"},
				},
			},
		}
		tgs = []*targetgroup.Group{
			{
				Targets: []model.LabelSet{
					{model.AddressLabel: "127.0.0.1:9090"},
					{model.AddressLabel: "127.0.0.1:9091"},
				},
			},
		}
		sp, _                  = newScrapePool(cfg, app, 0, nil, nil, &Options{}, newTestScrapeMetrics(t))
		expectedLabelSetString = "{__address__=\"127.0.0.1:9090\", __scrape_interval__=\"0s\", __scrape_timeout__=\"0s\", job=\"dropMe\"}"
		expectedLength         = 2
	)
	sp.Sync(tgs)
	sp.Sync(tgs)
	require.Len(t, sp.droppedTargets, expectedLength)
	require.Equal(t, expectedLength, sp.droppedTargetsCount)
	lb := labels.NewBuilder(labels.EmptyLabels())
	require.Equal(t, expectedLabelSetString, sp.droppedTargets[0].DiscoveredLabels(lb).String())

	// Check that count is still correct when we don't retain all dropped targets.
	sp.config.KeepDroppedTargets = 1
	sp.Sync(tgs)
	require.Len(t, sp.droppedTargets, 1)
	require.Equal(t, expectedLength, sp.droppedTargetsCount)
}

// TestDiscoveredLabelsUpdate checks that DiscoveredLabels are updated
// even when new labels don't affect the target `hash`.
func TestDiscoveredLabelsUpdate(t *testing.T) {
	sp := &scrapePool{
		metrics: newTestScrapeMetrics(t),
	}

	// These are used when syncing so need this to avoid a panic.
	sp.config = &config.ScrapeConfig{
		ScrapeInterval: model.Duration(1),
		ScrapeTimeout:  model.Duration(1),
	}
	sp.activeTargets = make(map[uint64]*Target)
	t1 := &Target{
		tLabels:      model.LabelSet{"label": "name"},
		scrapeConfig: sp.config,
	}
	sp.activeTargets[t1.hash()] = t1

	t2 := &Target{
		tLabels:      model.LabelSet{"labelNew": "nameNew"},
		scrapeConfig: sp.config,
	}
	sp.sync([]*Target{t2})

	lb := labels.NewBuilder(labels.EmptyLabels())
	require.Equal(t, t2.DiscoveredLabels(lb), sp.activeTargets[t1.hash()].DiscoveredLabels(lb))
}

type testLoop struct {
	startFunc    func(interval, timeout time.Duration, errc chan<- error)
	stopFunc     func()
	forcedErr    error
	forcedErrMtx sync.Mutex
	runOnce      bool
	interval     time.Duration
	timeout      time.Duration
}

func (l *testLoop) setScrapeFailureLogger(*logging.JSONFileLogger) {
}

func (l *testLoop) run(errc chan<- error) {
	if l.runOnce {
		panic("loop must be started only once")
	}
	l.runOnce = true
	l.startFunc(l.interval, l.timeout, errc)
}

func (l *testLoop) disableEndOfRunStalenessMarkers() {
}

func (l *testLoop) setForcedError(err error) {
	l.forcedErrMtx.Lock()
	defer l.forcedErrMtx.Unlock()
	l.forcedErr = err
}

func (l *testLoop) getForcedError() error {
	l.forcedErrMtx.Lock()
	defer l.forcedErrMtx.Unlock()
	return l.forcedErr
}

func (l *testLoop) stop() {
	l.stopFunc()
}

func (l *testLoop) getCache() *scrapeCache {
	return nil
}

func TestScrapePoolStop(t *testing.T) {
	sp := &scrapePool{
		activeTargets: map[uint64]*Target{},
		loops:         map[uint64]loop{},
		cancel:        func() {},
		client:        http.DefaultClient,
		metrics:       newTestScrapeMetrics(t),
	}
	var mtx sync.Mutex
	stopped := map[uint64]bool{}
	numTargets := 20

	// Stopping the scrape pool must call stop() on all scrape loops,
	// clean them and the respective targets up. It must wait until each loop's
	// stop function returned before returning itself.

	for i := 0; i < numTargets; i++ {
		t := &Target{
			labels:       labels.FromStrings(model.AddressLabel, fmt.Sprintf("example.com:%d", i)),
			scrapeConfig: &config.ScrapeConfig{},
		}
		l := &testLoop{}
		d := time.Duration((i+1)*20) * time.Millisecond
		l.stopFunc = func() {
			time.Sleep(d)

			mtx.Lock()
			stopped[t.hash()] = true
			mtx.Unlock()
		}

		sp.activeTargets[t.hash()] = t
		sp.loops[t.hash()] = l
	}

	done := make(chan struct{})
	stopTime := time.Now()

	go func() {
		sp.stop()
		close(done)
	}()

	select {
	case <-time.After(5 * time.Second):
		require.Fail(t, "scrapeLoop.stop() did not return as expected")
	case <-done:
		// This should have taken at least as long as the last target slept.
		require.GreaterOrEqual(t, time.Since(stopTime), time.Duration(numTargets*20)*time.Millisecond, "scrapeLoop.stop() exited before all targets stopped")
	}

	mtx.Lock()
	require.Len(t, stopped, numTargets, "Unexpected number of stopped loops")
	mtx.Unlock()

	require.Empty(t, sp.activeTargets, "Targets were not cleared on stopping: %d left", len(sp.activeTargets))
	require.Empty(t, sp.loops, "Loops were not cleared on stopping: %d left", len(sp.loops))
}

func TestScrapePoolReload(t *testing.T) {
	var mtx sync.Mutex
	numTargets := 20

	stopped := map[uint64]bool{}

	reloadCfg := &config.ScrapeConfig{
		ScrapeInterval: model.Duration(3 * time.Second),
		ScrapeTimeout:  model.Duration(2 * time.Second),
	}
	// On starting to run, new loops created on reload check whether their preceding
	// equivalents have been stopped.
	newLoop := func(opts scrapeLoopOptions) loop {
		l := &testLoop{interval: time.Duration(reloadCfg.ScrapeInterval), timeout: time.Duration(reloadCfg.ScrapeTimeout)}
		l.startFunc = func(interval, timeout time.Duration, errc chan<- error) {
			require.Equal(t, 3*time.Second, interval, "Unexpected scrape interval")
			require.Equal(t, 2*time.Second, timeout, "Unexpected scrape timeout")

			mtx.Lock()
			targetScraper := opts.scraper.(*targetScraper)
			require.True(t, stopped[targetScraper.hash()], "Scrape loop for %v not stopped yet", targetScraper)
			mtx.Unlock()
		}
		return l
	}

	reg, metrics := newTestRegistryAndScrapeMetrics(t)
	sp := &scrapePool{
		appendable:    &nopAppendable{},
		activeTargets: map[uint64]*Target{},
		loops:         map[uint64]loop{},
		newLoop:       newLoop,
		logger:        nil,
		client:        http.DefaultClient,
		metrics:       metrics,
		symbolTable:   labels.NewSymbolTable(),
	}

	// Reloading a scrape pool with a new scrape configuration must stop all scrape
	// loops and start new ones. A new loop must not be started before the preceding
	// one terminated.

	for i := 0; i < numTargets; i++ {
		labels := labels.FromStrings(model.AddressLabel, fmt.Sprintf("example.com:%d", i))
		t := &Target{
			labels:       labels,
			scrapeConfig: &config.ScrapeConfig{},
		}
		l := &testLoop{}
		d := time.Duration((i+1)*20) * time.Millisecond
		l.stopFunc = func() {
			time.Sleep(d)

			mtx.Lock()
			stopped[t.hash()] = true
			mtx.Unlock()
		}

		sp.activeTargets[t.hash()] = t
		sp.loops[t.hash()] = l
	}
	done := make(chan struct{})

	beforeTargets := map[uint64]*Target{}
	for h, t := range sp.activeTargets {
		beforeTargets[h] = t
	}

	reloadTime := time.Now()

	go func() {
		sp.reload(reloadCfg)
		close(done)
	}()

	select {
	case <-time.After(5 * time.Second):
		require.FailNow(t, "scrapeLoop.reload() did not return as expected")
	case <-done:
		// This should have taken at least as long as the last target slept.
		require.GreaterOrEqual(t, time.Since(reloadTime), time.Duration(numTargets*20)*time.Millisecond, "scrapeLoop.stop() exited before all targets stopped")
	}

	mtx.Lock()
	require.Len(t, stopped, numTargets, "Unexpected number of stopped loops")
	mtx.Unlock()

	require.Equal(t, sp.activeTargets, beforeTargets, "Reloading affected target states unexpectedly")
	require.Len(t, sp.loops, numTargets, "Unexpected number of stopped loops after reload")

	got, err := gatherLabels(reg, "prometheus_target_reload_length_seconds")
	require.NoError(t, err)
	expectedName, expectedValue := "interval", "3s"
	require.Equal(t, [][]*dto.LabelPair{{{Name: &expectedName, Value: &expectedValue}}}, got)
	require.Equal(t, 1.0, prom_testutil.ToFloat64(sp.metrics.targetScrapePoolReloads))
}

func TestScrapePoolReloadPreserveRelabeledIntervalTimeout(t *testing.T) {
	reloadCfg := &config.ScrapeConfig{
		ScrapeInterval: model.Duration(3 * time.Second),
		ScrapeTimeout:  model.Duration(2 * time.Second),
	}
	newLoop := func(opts scrapeLoopOptions) loop {
		l := &testLoop{interval: opts.interval, timeout: opts.timeout}
		l.startFunc = func(interval, timeout time.Duration, errc chan<- error) {
			require.Equal(t, 5*time.Second, interval, "Unexpected scrape interval")
			require.Equal(t, 3*time.Second, timeout, "Unexpected scrape timeout")
		}
		return l
	}
	reg, metrics := newTestRegistryAndScrapeMetrics(t)
	sp := &scrapePool{
		appendable: &nopAppendable{},
		activeTargets: map[uint64]*Target{
			1: {
				labels: labels.FromStrings(model.ScrapeIntervalLabel, "5s", model.ScrapeTimeoutLabel, "3s"),
			},
		},
		loops: map[uint64]loop{
			1: noopLoop(),
		},
		newLoop:     newLoop,
		logger:      nil,
		client:      http.DefaultClient,
		metrics:     metrics,
		symbolTable: labels.NewSymbolTable(),
	}

	err := sp.reload(reloadCfg)
	if err != nil {
		t.Fatalf("unable to reload configuration: %s", err)
	}
	// Check that the reload metric is labeled with the pool interval, not the overridden interval.
	got, err := gatherLabels(reg, "prometheus_target_reload_length_seconds")
	require.NoError(t, err)
	expectedName, expectedValue := "interval", "3s"
	require.Equal(t, [][]*dto.LabelPair{{{Name: &expectedName, Value: &expectedValue}}}, got)
}

// Gather metrics from the provided Gatherer with specified familyName,
// and return all sets of name/value pairs.
func gatherLabels(g prometheus.Gatherer, familyName string) ([][]*dto.LabelPair, error) {
	families, err := g.Gather()
	if err != nil {
		return nil, err
	}
	ret := make([][]*dto.LabelPair, 0)
	for _, f := range families {
		if f.GetName() == familyName {
			for _, m := range f.GetMetric() {
				ret = append(ret, m.GetLabel())
			}
			break
		}
	}
	return ret, nil
}

func TestScrapePoolTargetLimit(t *testing.T) {
	var wg sync.WaitGroup
	// On starting to run, new loops created on reload check whether their preceding
	// equivalents have been stopped.
	newLoop := func(opts scrapeLoopOptions) loop {
		wg.Add(1)
		l := &testLoop{
			startFunc: func(interval, timeout time.Duration, errc chan<- error) {
				wg.Done()
			},
			stopFunc: func() {},
		}
		return l
	}
	sp := &scrapePool{
		appendable:    &nopAppendable{},
		activeTargets: map[uint64]*Target{},
		loops:         map[uint64]loop{},
		newLoop:       newLoop,
		logger:        promslog.NewNopLogger(),
		client:        http.DefaultClient,
		metrics:       newTestScrapeMetrics(t),
		symbolTable:   labels.NewSymbolTable(),
	}

	tgs := []*targetgroup.Group{}
	for i := 0; i < 50; i++ {
		tgs = append(tgs,
			&targetgroup.Group{
				Targets: []model.LabelSet{
					{model.AddressLabel: model.LabelValue(fmt.Sprintf("127.0.0.1:%d", 9090+i))},
				},
			},
		)
	}

	var limit uint
	reloadWithLimit := func(l uint) {
		limit = l
		require.NoError(t, sp.reload(&config.ScrapeConfig{
			ScrapeInterval: model.Duration(3 * time.Second),
			ScrapeTimeout:  model.Duration(2 * time.Second),
			TargetLimit:    l,
		}))
	}

	var targets int
	loadTargets := func(n int) {
		targets = n
		sp.Sync(tgs[:n])
	}

	validateIsRunning := func() {
		wg.Wait()
		for _, l := range sp.loops {
			require.True(t, l.(*testLoop).runOnce, "loop should be running")
		}
	}

	validateErrorMessage := func(shouldErr bool) {
		for _, l := range sp.loops {
			lerr := l.(*testLoop).getForcedError()
			if shouldErr {
				require.Error(t, lerr, "error was expected for %d targets with a limit of %d", targets, limit)
				require.EqualError(t, lerr, fmt.Sprintf("target_limit exceeded (number of targets: %d, limit: %d)", targets, limit))
			} else {
				require.NoError(t, lerr)
			}
		}
	}

	reloadWithLimit(0)
	loadTargets(50)
	validateIsRunning()

	// Simulate an initial config with a limit.
	sp.config.TargetLimit = 30
	limit = 30
	loadTargets(50)
	validateIsRunning()
	validateErrorMessage(true)

	reloadWithLimit(50)
	validateIsRunning()
	validateErrorMessage(false)

	reloadWithLimit(40)
	validateIsRunning()
	validateErrorMessage(true)

	loadTargets(30)
	validateIsRunning()
	validateErrorMessage(false)

	loadTargets(40)
	validateIsRunning()
	validateErrorMessage(false)

	loadTargets(41)
	validateIsRunning()
	validateErrorMessage(true)

	reloadWithLimit(0)
	validateIsRunning()
	validateErrorMessage(false)

	reloadWithLimit(51)
	validateIsRunning()
	validateErrorMessage(false)

	tgs = append(tgs,
		&targetgroup.Group{
			Targets: []model.LabelSet{
				{model.AddressLabel: model.LabelValue("127.0.0.1:1090")},
			},
		},
		&targetgroup.Group{
			Targets: []model.LabelSet{
				{model.AddressLabel: model.LabelValue("127.0.0.1:1090")},
			},
		},
	)

	sp.Sync(tgs)
	validateIsRunning()
	validateErrorMessage(false)
}

func TestScrapePoolAppender(t *testing.T) {
	cfg := &config.ScrapeConfig{}
	app := &nopAppendable{}
	sp, _ := newScrapePool(cfg, app, 0, nil, nil, &Options{}, newTestScrapeMetrics(t))

	loop := sp.newLoop(scrapeLoopOptions{
		target: &Target{},
	})
	appl, ok := loop.(*scrapeLoop)
	require.True(t, ok, "Expected scrapeLoop but got %T", loop)

	wrapped := appender(appl.appender(context.Background()), 0, 0, histogram.ExponentialSchemaMax)

	tl, ok := wrapped.(*timeLimitAppender)
	require.True(t, ok, "Expected timeLimitAppender but got %T", wrapped)

	_, ok = tl.Appender.(nopAppender)
	require.True(t, ok, "Expected base appender but got %T", tl.Appender)

	sampleLimit := 100
	loop = sp.newLoop(scrapeLoopOptions{
		target:      &Target{},
		sampleLimit: sampleLimit,
	})
	appl, ok = loop.(*scrapeLoop)
	require.True(t, ok, "Expected scrapeLoop but got %T", loop)

	wrapped = appender(appl.appender(context.Background()), sampleLimit, 0, histogram.ExponentialSchemaMax)

	sl, ok := wrapped.(*limitAppender)
	require.True(t, ok, "Expected limitAppender but got %T", wrapped)

	tl, ok = sl.Appender.(*timeLimitAppender)
	require.True(t, ok, "Expected timeLimitAppender but got %T", sl.Appender)

	_, ok = tl.Appender.(nopAppender)
	require.True(t, ok, "Expected base appender but got %T", tl.Appender)

	wrapped = appender(appl.appender(context.Background()), sampleLimit, 100, histogram.ExponentialSchemaMax)

	bl, ok := wrapped.(*bucketLimitAppender)
	require.True(t, ok, "Expected bucketLimitAppender but got %T", wrapped)

	sl, ok = bl.Appender.(*limitAppender)
	require.True(t, ok, "Expected limitAppender but got %T", bl)

	tl, ok = sl.Appender.(*timeLimitAppender)
	require.True(t, ok, "Expected timeLimitAppender but got %T", sl.Appender)

	_, ok = tl.Appender.(nopAppender)
	require.True(t, ok, "Expected base appender but got %T", tl.Appender)

	wrapped = appender(appl.appender(context.Background()), sampleLimit, 100, 0)

	ml, ok := wrapped.(*maxSchemaAppender)
	require.True(t, ok, "Expected maxSchemaAppender but got %T", wrapped)

	bl, ok = ml.Appender.(*bucketLimitAppender)
	require.True(t, ok, "Expected bucketLimitAppender but got %T", wrapped)

	sl, ok = bl.Appender.(*limitAppender)
	require.True(t, ok, "Expected limitAppender but got %T", bl)

	tl, ok = sl.Appender.(*timeLimitAppender)
	require.True(t, ok, "Expected timeLimitAppender but got %T", sl.Appender)

	_, ok = tl.Appender.(nopAppender)
	require.True(t, ok, "Expected base appender but got %T", tl.Appender)
}

func TestScrapePoolRaces(t *testing.T) {
	interval, _ := model.ParseDuration("1s")
	timeout, _ := model.ParseDuration("500ms")
	newConfig := func() *config.ScrapeConfig {
		return &config.ScrapeConfig{ScrapeInterval: interval, ScrapeTimeout: timeout}
	}
	sp, _ := newScrapePool(newConfig(), &nopAppendable{}, 0, nil, nil, &Options{}, newTestScrapeMetrics(t))
	tgts := []*targetgroup.Group{
		{
			Targets: []model.LabelSet{
				{model.AddressLabel: "127.0.0.1:9090"},
				{model.AddressLabel: "127.0.0.2:9090"},
				{model.AddressLabel: "127.0.0.3:9090"},
				{model.AddressLabel: "127.0.0.4:9090"},
				{model.AddressLabel: "127.0.0.5:9090"},
				{model.AddressLabel: "127.0.0.6:9090"},
				{model.AddressLabel: "127.0.0.7:9090"},
				{model.AddressLabel: "127.0.0.8:9090"},
			},
		},
	}

	sp.Sync(tgts)
	active := sp.ActiveTargets()
	dropped := sp.DroppedTargets()
	expectedActive, expectedDropped := len(tgts[0].Targets), 0

	require.Len(t, active, expectedActive, "Invalid number of active targets")
	require.Len(t, dropped, expectedDropped, "Invalid number of dropped targets")

	for i := 0; i < 20; i++ {
		time.Sleep(10 * time.Millisecond)
		sp.reload(newConfig())
	}
	sp.stop()
}

func TestScrapePoolScrapeLoopsStarted(t *testing.T) {
	var wg sync.WaitGroup
	newLoop := func(opts scrapeLoopOptions) loop {
		wg.Add(1)
		l := &testLoop{
			startFunc: func(interval, timeout time.Duration, errc chan<- error) {
				wg.Done()
			},
			stopFunc: func() {},
		}
		return l
	}
	sp := &scrapePool{
		appendable:    &nopAppendable{},
		activeTargets: map[uint64]*Target{},
		loops:         map[uint64]loop{},
		newLoop:       newLoop,
		logger:        nil,
		client:        http.DefaultClient,
		metrics:       newTestScrapeMetrics(t),
		symbolTable:   labels.NewSymbolTable(),
	}

	tgs := []*targetgroup.Group{
		{
			Targets: []model.LabelSet{
				{model.AddressLabel: model.LabelValue("127.0.0.1:9090")},
			},
		},
		{
			Targets: []model.LabelSet{
				{model.AddressLabel: model.LabelValue("127.0.0.1:9090")},
			},
		},
	}

	require.NoError(t, sp.reload(&config.ScrapeConfig{
		ScrapeInterval: model.Duration(3 * time.Second),
		ScrapeTimeout:  model.Duration(2 * time.Second),
	}))
	sp.Sync(tgs)

	require.Len(t, sp.loops, 1)

	wg.Wait()
	for _, l := range sp.loops {
		require.True(t, l.(*testLoop).runOnce, "loop should be running")
	}
}

func newBasicScrapeLoop(t testing.TB, ctx context.Context, scraper scraper, app func(ctx context.Context) storage.Appender, interval time.Duration) *scrapeLoop {
	return newBasicScrapeLoopWithFallback(t, ctx, scraper, app, interval, "")
}

func newBasicScrapeLoopWithFallback(t testing.TB, ctx context.Context, scraper scraper, app func(ctx context.Context) storage.Appender, interval time.Duration, fallback string) *scrapeLoop {
	return newScrapeLoop(ctx,
		scraper,
		nil, nil,
		nopMutator,
		nopMutator,
		app,
		nil,
		labels.NewSymbolTable(),
		0,
		true,
		false,
		true,
		0, 0, histogram.ExponentialSchemaMax,
		nil,
		interval,
		time.Hour,
		false,
		false,
		false,
		false,
		false,
		false,
		nil,
		false,
		newTestScrapeMetrics(t),
		false,
		model.LegacyValidation,
		fallback,
	)
}

func TestScrapeLoopStopBeforeRun(t *testing.T) {
	scraper := &testScraper{}
	sl := newBasicScrapeLoop(t, context.Background(), scraper, nil, 1)

	// The scrape pool synchronizes on stopping scrape loops. However, new scrape
	// loops are started asynchronously. Thus it's possible, that a loop is stopped
	// again before having started properly.
	// Stopping not-yet-started loops must block until the run method was called and exited.
	// The run method must exit immediately.

	stopDone := make(chan struct{})
	go func() {
		sl.stop()
		close(stopDone)
	}()

	select {
	case <-stopDone:
		require.FailNow(t, "Stopping terminated before run exited successfully.")
	case <-time.After(500 * time.Millisecond):
	}

	// Running the scrape loop must exit before calling the scraper even once.
	scraper.scrapeFunc = func(context.Context, io.Writer) error {
		require.FailNow(t, "Scraper was called for terminated scrape loop.")
		return nil
	}

	runDone := make(chan struct{})
	go func() {
		sl.run(nil)
		close(runDone)
	}()

	select {
	case <-runDone:
	case <-time.After(1 * time.Second):
		require.FailNow(t, "Running terminated scrape loop did not exit.")
	}

	select {
	case <-stopDone:
	case <-time.After(1 * time.Second):
		require.FailNow(t, "Stopping did not terminate after running exited.")
	}
}

func nopMutator(l labels.Labels) labels.Labels { return l }

func TestScrapeLoopStop(t *testing.T) {
	var (
		signal   = make(chan struct{}, 1)
		appender = &collectResultAppender{}
		scraper  = &testScraper{}
		app      = func(ctx context.Context) storage.Appender { return appender }
	)

	// Since we're writing samples directly below we need to provide a protocol fallback.
	sl := newBasicScrapeLoopWithFallback(t, context.Background(), scraper, app, 10*time.Millisecond, "text/plain")

	// Terminate loop after 2 scrapes.
	numScrapes := 0

	scraper.scrapeFunc = func(ctx context.Context, w io.Writer) error {
		numScrapes++
		if numScrapes == 2 {
			go sl.stop()
			<-sl.ctx.Done()
		}
		w.Write([]byte("metric_a 42\n"))
		return ctx.Err()
	}

	go func() {
		sl.run(nil)
		signal <- struct{}{}
	}()

	select {
	case <-signal:
	case <-time.After(5 * time.Second):
		require.FailNow(t, "Scrape wasn't stopped.")
	}

	// We expected 1 actual sample for each scrape plus 5 for report samples.
	// At least 2 scrapes were made, plus the final stale markers.
	require.GreaterOrEqual(t, len(appender.resultFloats), 6*3, "Expected at least 3 scrapes with 6 samples each.")
	require.Zero(t, len(appender.resultFloats)%6, "There is a scrape with missing samples.")
	// All samples in a scrape must have the same timestamp.
	var ts int64
	for i, s := range appender.resultFloats {
		switch {
		case i%6 == 0:
			ts = s.t
		case s.t != ts:
			t.Fatalf("Unexpected multiple timestamps within single scrape")
		}
	}
	// All samples from the last scrape must be stale markers.
	for _, s := range appender.resultFloats[len(appender.resultFloats)-5:] {
		require.True(t, value.IsStaleNaN(s.f), "Appended last sample not as expected. Wanted: stale NaN Got: %x", math.Float64bits(s.f))
	}
}

func TestScrapeLoopRun(t *testing.T) {
	var (
		signal = make(chan struct{}, 1)
		errc   = make(chan error)

		scraper       = &testScraper{}
		app           = func(ctx context.Context) storage.Appender { return &nopAppender{} }
		scrapeMetrics = newTestScrapeMetrics(t)
	)

	ctx, cancel := context.WithCancel(context.Background())
	sl := newScrapeLoop(ctx,
		scraper,
		nil, nil,
		nopMutator,
		nopMutator,
		app,
		nil,
		nil,
		0,
		true,
		false,
		true,
		0, 0, histogram.ExponentialSchemaMax,
		nil,
		time.Second,
		time.Hour,
		false,
		false,
		false,
		false,
		false,
		false,
		nil,
		false,
		scrapeMetrics,
		false,
		model.LegacyValidation,
		"",
	)

	// The loop must terminate during the initial offset if the context
	// is canceled.
	scraper.offsetDur = time.Hour

	go func() {
		sl.run(errc)
		signal <- struct{}{}
	}()

	// Wait to make sure we are actually waiting on the offset.
	time.Sleep(1 * time.Second)

	cancel()
	select {
	case <-signal:
	case <-time.After(5 * time.Second):
		require.FailNow(t, "Cancellation during initial offset failed.")
	case err := <-errc:
		require.FailNow(t, "Unexpected error: %s", err)
	}

	// The provided timeout must cause cancellation of the context passed down to the
	// scraper. The scraper has to respect the context.
	scraper.offsetDur = 0

	block := make(chan struct{})
	scraper.scrapeFunc = func(ctx context.Context, _ io.Writer) error {
		select {
		case <-block:
		case <-ctx.Done():
			return ctx.Err()
		}
		return nil
	}

	ctx, cancel = context.WithCancel(context.Background())
	sl = newBasicScrapeLoop(t, ctx, scraper, app, time.Second)
	sl.timeout = 100 * time.Millisecond

	go func() {
		sl.run(errc)
		signal <- struct{}{}
	}()

	select {
	case err := <-errc:
		require.ErrorIs(t, err, context.DeadlineExceeded)
	case <-time.After(3 * time.Second):
		require.FailNow(t, "Expected timeout error but got none.")
	}

	// We already caught the timeout error and are certainly in the loop.
	// Let the scrapes returns immediately to cause no further timeout errors
	// and check whether canceling the parent context terminates the loop.
	close(block)
	cancel()

	select {
	case <-signal:
		// Loop terminated as expected.
	case err := <-errc:
		require.FailNow(t, "Unexpected error: %s", err)
	case <-time.After(3 * time.Second):
		require.FailNow(t, "Loop did not terminate on context cancellation")
	}
}

func TestScrapeLoopForcedErr(t *testing.T) {
	var (
		signal = make(chan struct{}, 1)
		errc   = make(chan error)

		scraper = &testScraper{}
		app     = func(ctx context.Context) storage.Appender { return &nopAppender{} }
	)

	ctx, cancel := context.WithCancel(context.Background())
	sl := newBasicScrapeLoop(t, ctx, scraper, app, time.Second)

	forcedErr := errors.New("forced err")
	sl.setForcedError(forcedErr)

	scraper.scrapeFunc = func(context.Context, io.Writer) error {
		require.FailNow(t, "Should not be scraped.")
		return nil
	}

	go func() {
		sl.run(errc)
		signal <- struct{}{}
	}()

	select {
	case err := <-errc:
		require.ErrorIs(t, err, forcedErr)
	case <-time.After(3 * time.Second):
		require.FailNow(t, "Expected forced error but got none.")
	}
	cancel()

	select {
	case <-signal:
	case <-time.After(5 * time.Second):
		require.FailNow(t, "Scrape not stopped.")
	}
}

func TestScrapeLoopMetadata(t *testing.T) {
	var (
		signal        = make(chan struct{})
		scraper       = &testScraper{}
		scrapeMetrics = newTestScrapeMetrics(t)
		cache         = newScrapeCache(scrapeMetrics)
	)
	defer close(signal)

	ctx, cancel := context.WithCancel(context.Background())
	sl := newScrapeLoop(ctx,
		scraper,
		nil, nil,
		nopMutator,
		nopMutator,
		func(ctx context.Context) storage.Appender { return nopAppender{} },
		cache,
		labels.NewSymbolTable(),
		0,
		true,
		false,
		true,
		0, 0, histogram.ExponentialSchemaMax,
		nil,
		0,
		0,
		false,
		false,
		false,
		false,
		false,
		false,
		nil,
		false,
		scrapeMetrics,
		false,
		model.LegacyValidation,
		"",
	)
	defer cancel()

	slApp := sl.appender(ctx)
	total, _, _, err := sl.append(slApp, []byte(`# TYPE test_metric counter
# HELP test_metric some help text
# UNIT test_metric metric
test_metric 1
# TYPE test_metric_no_help gauge
# HELP test_metric_no_type other help text
# EOF`), "application/openmetrics-text", time.Now())
	require.NoError(t, err)
	require.NoError(t, slApp.Commit())
	require.Equal(t, 1, total)

	md, ok := cache.GetMetadata("test_metric")
	require.True(t, ok, "expected metadata to be present")
	require.Equal(t, model.MetricTypeCounter, md.Type, "unexpected metric type")
	require.Equal(t, "some help text", md.Help)
	require.Equal(t, "metric", md.Unit)

	md, ok = cache.GetMetadata("test_metric_no_help")
	require.True(t, ok, "expected metadata to be present")
	require.Equal(t, model.MetricTypeGauge, md.Type, "unexpected metric type")
	require.Equal(t, "", md.Help)
	require.Equal(t, "", md.Unit)

	md, ok = cache.GetMetadata("test_metric_no_type")
	require.True(t, ok, "expected metadata to be present")
	require.Equal(t, model.MetricTypeUnknown, md.Type, "unexpected metric type")
	require.Equal(t, "other help text", md.Help)
	require.Equal(t, "", md.Unit)
}

func simpleTestScrapeLoop(t testing.TB) (context.Context, *scrapeLoop) {
	// Need a full storage for correct Add/AddFast semantics.
	s := teststorage.New(t)
	t.Cleanup(func() { s.Close() })

	ctx, cancel := context.WithCancel(context.Background())
	sl := newBasicScrapeLoop(t, ctx, &testScraper{}, s.Appender, 0)
	t.Cleanup(func() { cancel() })

	return ctx, sl
}

func TestScrapeLoopSeriesAdded(t *testing.T) {
	ctx, sl := simpleTestScrapeLoop(t)

	slApp := sl.appender(ctx)
	total, added, seriesAdded, err := sl.append(slApp, []byte("test_metric 1\n"), "text/plain", time.Time{})
	require.NoError(t, err)
	require.NoError(t, slApp.Commit())
	require.Equal(t, 1, total)
	require.Equal(t, 1, added)
	require.Equal(t, 1, seriesAdded)

	slApp = sl.appender(ctx)
	total, added, seriesAdded, err = sl.append(slApp, []byte("test_metric 1\n"), "text/plain", time.Time{})
	require.NoError(t, slApp.Commit())
	require.NoError(t, err)
	require.Equal(t, 1, total)
	require.Equal(t, 1, added)
	require.Equal(t, 0, seriesAdded)
}

func TestScrapeLoopFailWithInvalidLabelsAfterRelabel(t *testing.T) {
	model.NameValidationScheme = model.LegacyValidation
	s := teststorage.New(t)
	defer s.Close()
	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()

	target := &Target{
		labels: labels.FromStrings("pod_label_invalid_012", "test"),
	}
	relabelConfig := []*relabel.Config{{
		Action:      relabel.LabelMap,
		Regex:       relabel.MustNewRegexp("pod_label_invalid_(.+)"),
		Separator:   ";",
		Replacement: "$1",
	}}
	sl := newBasicScrapeLoop(t, ctx, &testScraper{}, s.Appender, 0)
	sl.sampleMutator = func(l labels.Labels) labels.Labels {
		return mutateSampleLabels(l, target, true, relabelConfig)
	}

	slApp := sl.appender(ctx)
	total, added, seriesAdded, err := sl.append(slApp, []byte("test_metric 1\n"), "text/plain", time.Time{})
	require.ErrorContains(t, err, "invalid metric name or label names")
	require.NoError(t, slApp.Rollback())
	require.Equal(t, 1, total)
	require.Equal(t, 0, added)
	require.Equal(t, 0, seriesAdded)
}

func TestScrapeLoopFailLegacyUnderUTF8(t *testing.T) {
	// Test that scrapes fail when default validation is utf8 but scrape config is
	// legacy.
	model.NameValidationScheme = model.UTF8Validation
	defer func() {
		model.NameValidationScheme = model.LegacyValidation
	}()
	s := teststorage.New(t)
	defer s.Close()
	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()

	sl := newBasicScrapeLoop(t, ctx, &testScraper{}, s.Appender, 0)
	sl.validationScheme = model.LegacyValidation

	slApp := sl.appender(ctx)
	total, added, seriesAdded, err := sl.append(slApp, []byte("{\"test.metric\"} 1\n"), "text/plain", time.Time{})
	require.ErrorContains(t, err, "invalid metric name or label names")
	require.NoError(t, slApp.Rollback())
	require.Equal(t, 1, total)
	require.Equal(t, 0, added)
	require.Equal(t, 0, seriesAdded)

	// When scrapeloop has validation set to UTF-8, the metric is allowed.
	sl.validationScheme = model.UTF8Validation

	slApp = sl.appender(ctx)
	total, added, seriesAdded, err = sl.append(slApp, []byte("{\"test.metric\"} 1\n"), "text/plain", time.Time{})
	require.NoError(t, err)
	require.Equal(t, 1, total)
	require.Equal(t, 1, added)
	require.Equal(t, 1, seriesAdded)
}

func makeTestMetrics(n int) []byte {
	// Construct a metrics string to parse
	sb := bytes.Buffer{}
	fmt.Fprintf(&sb, "# TYPE metric_a gauge\n")
	fmt.Fprintf(&sb, "# HELP metric_a help text\n")
	for i := 0; i < n; i++ {
		fmt.Fprintf(&sb, "metric_a{foo=\"%d\",bar=\"%d\"} 1\n", i, i*100)
	}
	fmt.Fprintf(&sb, "# EOF\n")
	return sb.Bytes()
}

func promTextToProto(tb testing.TB, text []byte) []byte {
	tb.Helper()

	d := expfmt.NewDecoder(bytes.NewReader(text), expfmt.TextVersion)

	pb := &dto.MetricFamily{}
	if err := d.Decode(pb); err != nil {
		tb.Fatal(err)
	}
	o, err := proto.Marshal(pb)
	if err != nil {
		tb.Fatal(err)
	}
	buf := bytes.Buffer{}
	// Write first length, then binary protobuf.
	varintBuf := binary.AppendUvarint(nil, uint64(len(o)))
	buf.Write(varintBuf)
	buf.Write(o)
	return buf.Bytes()
}

/*
	export bench=scrape-loop-v1 && go test \
		-run '^$' -bench '^BenchmarkScrapeLoopAppend' \
		-benchtime 5s -count 6 -cpu 2 -timeout 999m \
		| tee ${bench}.txt
*/
func BenchmarkScrapeLoopAppend(b *testing.B) {
	metricsText := makeTestMetrics(100)

	// Create proto representation.
	metricsProto := promTextToProto(b, metricsText)

	for _, bcase := range []struct {
		name        string
		contentType string
		parsable    []byte
	}{
		{name: "PromText", contentType: "text/plain", parsable: metricsText},
		{name: "OMText", contentType: "application/openmetrics-text", parsable: metricsText},
		{name: "PromProto", contentType: "application/vnd.google.protobuf", parsable: metricsProto},
	} {
		b.Run(fmt.Sprintf("fmt=%v", bcase.name), func(b *testing.B) {
			ctx, sl := simpleTestScrapeLoop(b)

			slApp := sl.appender(ctx)
			ts := time.Time{}

			b.ReportAllocs()
			b.ResetTimer()
			for i := 0; i < b.N; i++ {
				ts = ts.Add(time.Second)
				_, _, _, err := sl.append(slApp, bcase.parsable, bcase.contentType, ts)
				if err != nil {
					b.Fatal(err)
				}
			}
		})
	}
}

func TestSetOptionsHandlingStaleness(t *testing.T) {
	s := teststorage.New(t, 600000)
	defer s.Close()

	signal := make(chan struct{}, 1)
	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()

	// Function to run the scrape loop
	runScrapeLoop := func(ctx context.Context, t *testing.T, cue int, action func(*scrapeLoop)) {
		var (
			scraper = &testScraper{}
			app     = func(ctx context.Context) storage.Appender {
				return s.Appender(ctx)
			}
		)
		sl := newBasicScrapeLoop(t, ctx, scraper, app, 10*time.Millisecond)
		numScrapes := 0
		scraper.scrapeFunc = func(ctx context.Context, w io.Writer) error {
			numScrapes++
			if numScrapes == cue {
				action(sl)
			}
			w.Write([]byte(fmt.Sprintf("metric_a{a=\"1\",b=\"1\"} %d\n", 42+numScrapes)))
			return nil
		}
		sl.run(nil)
	}
	go func() {
		runScrapeLoop(ctx, t, 2, func(sl *scrapeLoop) {
			go sl.stop()
			// Wait a bit then start a new target.
			time.Sleep(100 * time.Millisecond)
			go func() {
				runScrapeLoop(ctx, t, 4, func(_ *scrapeLoop) {
					cancel()
				})
				signal <- struct{}{}
			}()
		})
	}()

	select {
	case <-signal:
	case <-time.After(10 * time.Second):
		t.Fatalf("Scrape wasn't stopped.")
	}

	ctx1, cancel := context.WithCancel(context.Background())
	defer cancel()

	q, err := s.Querier(0, time.Now().UnixNano())

	require.NoError(t, err)
	defer q.Close()

	series := q.Select(ctx1, false, nil, labels.MustNewMatcher(labels.MatchRegexp, "__name__", "metric_a"))

	var results []floatSample
	for series.Next() {
		it := series.At().Iterator(nil)
		for it.Next() == chunkenc.ValFloat {
			t, v := it.At()
			results = append(results, floatSample{
				metric: series.At().Labels(),
				t:      t,
				f:      v,
			})
		}
		require.NoError(t, it.Err())
	}
	require.NoError(t, series.Err())
	var c int
	for _, s := range results {
		if value.IsStaleNaN(s.f) {
			c++
		}
	}
	require.Equal(t, 0, c, "invalid count of staleness markers after stopping the engine")
}

func TestScrapeLoopRunCreatesStaleMarkersOnFailedScrape(t *testing.T) {
	appender := &collectResultAppender{}
	var (
		signal  = make(chan struct{}, 1)
		scraper = &testScraper{}
		app     = func(ctx context.Context) storage.Appender { return appender }
	)

	ctx, cancel := context.WithCancel(context.Background())
	// Since we're writing samples directly below we need to provide a protocol fallback.
	sl := newBasicScrapeLoopWithFallback(t, ctx, scraper, app, 10*time.Millisecond, "text/plain")
	// Succeed once, several failures, then stop.
	numScrapes := 0

	scraper.scrapeFunc = func(ctx context.Context, w io.Writer) error {
		numScrapes++

		switch numScrapes {
		case 1:
			w.Write([]byte("metric_a 42\n"))
			return nil
		case 5:
			cancel()
		}
		return errors.New("scrape failed")
	}

	go func() {
		sl.run(nil)
		signal <- struct{}{}
	}()

	select {
	case <-signal:
	case <-time.After(5 * time.Second):
		require.FailNow(t, "Scrape wasn't stopped.")
	}

	// 1 successfully scraped sample, 1 stale marker after first fail, 5 report samples for
	// each scrape successful or not.
	require.Len(t, appender.resultFloats, 27, "Appended samples not as expected:\n%s", appender)
	require.Equal(t, 42.0, appender.resultFloats[0].f, "Appended first sample not as expected")
	require.True(t, value.IsStaleNaN(appender.resultFloats[6].f),
		"Appended second sample not as expected. Wanted: stale NaN Got: %x", math.Float64bits(appender.resultFloats[6].f))
}

func TestScrapeLoopRunCreatesStaleMarkersOnParseFailure(t *testing.T) {
	appender := &collectResultAppender{}
	var (
		signal     = make(chan struct{}, 1)
		scraper    = &testScraper{}
		app        = func(ctx context.Context) storage.Appender { return appender }
		numScrapes = 0
	)

	ctx, cancel := context.WithCancel(context.Background())
	// Since we're writing samples directly below we need to provide a protocol fallback.
	sl := newBasicScrapeLoopWithFallback(t, ctx, scraper, app, 10*time.Millisecond, "text/plain")

	// Succeed once, several failures, then stop.
	scraper.scrapeFunc = func(ctx context.Context, w io.Writer) error {
		numScrapes++
		switch numScrapes {
		case 1:
			w.Write([]byte("metric_a 42\n"))
			return nil
		case 2:
			w.Write([]byte("7&-\n"))
			return nil
		case 3:
			cancel()
		}
		return errors.New("scrape failed")
	}

	go func() {
		sl.run(nil)
		signal <- struct{}{}
	}()

	select {
	case <-signal:
	case <-time.After(5 * time.Second):
		require.FailNow(t, "Scrape wasn't stopped.")
	}

	// 1 successfully scraped sample, 1 stale marker after first fail, 5 report samples for
	// each scrape successful or not.
	require.Len(t, appender.resultFloats, 17, "Appended samples not as expected:\n%s", appender)
	require.Equal(t, 42.0, appender.resultFloats[0].f, "Appended first sample not as expected")
	require.True(t, value.IsStaleNaN(appender.resultFloats[6].f),
		"Appended second sample not as expected. Wanted: stale NaN Got: %x", math.Float64bits(appender.resultFloats[6].f))
}

func TestScrapeLoopCache(t *testing.T) {
	s := teststorage.New(t)
	defer s.Close()

	appender := &collectResultAppender{}
	var (
		signal  = make(chan struct{}, 1)
		scraper = &testScraper{}
		app     = func(ctx context.Context) storage.Appender { appender.next = s.Appender(ctx); return appender }
	)

	ctx, cancel := context.WithCancel(context.Background())
	// Decreasing the scrape interval could make the test fail, as multiple scrapes might be initiated at identical millisecond timestamps.
	// See https://github.com/prometheus/prometheus/issues/12727.
	// Since we're writing samples directly below we need to provide a protocol fallback.
	sl := newBasicScrapeLoopWithFallback(t, ctx, scraper, app, 100*time.Millisecond, "text/plain")

	numScrapes := 0

	scraper.scrapeFunc = func(ctx context.Context, w io.Writer) error {
		switch numScrapes {
		case 1, 2:
			_, ok := sl.cache.series["metric_a"]
			require.True(t, ok, "metric_a missing from cache after scrape %d", numScrapes)
			_, ok = sl.cache.series["metric_b"]
			require.True(t, ok, "metric_b missing from cache after scrape %d", numScrapes)
		case 3:
			_, ok := sl.cache.series["metric_a"]
			require.True(t, ok, "metric_a missing from cache after scrape %d", numScrapes)
			_, ok = sl.cache.series["metric_b"]
			require.False(t, ok, "metric_b present in cache after scrape %d", numScrapes)
		}

		numScrapes++
		switch numScrapes {
		case 1:
			w.Write([]byte("metric_a 42\nmetric_b 43\n"))
			return nil
		case 3:
			w.Write([]byte("metric_a 44\n"))
			return nil
		case 4:
			cancel()
		}
		return errors.New("scrape failed")
	}

	go func() {
		sl.run(nil)
		signal <- struct{}{}
	}()

	select {
	case <-signal:
	case <-time.After(5 * time.Second):
		require.FailNow(t, "Scrape wasn't stopped.")
	}

	// 1 successfully scraped sample, 1 stale marker after first fail, 5 report samples for
	// each scrape successful or not.
	require.Len(t, appender.resultFloats, 26, "Appended samples not as expected:\n%s", appender)
}

func TestScrapeLoopCacheMemoryExhaustionProtection(t *testing.T) {
	s := teststorage.New(t)
	defer s.Close()

	sapp := s.Appender(context.Background())

	appender := &collectResultAppender{next: sapp}
	var (
		signal  = make(chan struct{}, 1)
		scraper = &testScraper{}
		app     = func(ctx context.Context) storage.Appender { return appender }
	)

	ctx, cancel := context.WithCancel(context.Background())
	sl := newBasicScrapeLoop(t, ctx, scraper, app, 10*time.Millisecond)

	numScrapes := 0

	scraper.scrapeFunc = func(ctx context.Context, w io.Writer) error {
		numScrapes++
		if numScrapes < 5 {
			s := ""
			for i := 0; i < 500; i++ {
				s = fmt.Sprintf("%smetric_%d_%d 42\n", s, i, numScrapes)
			}
			w.Write([]byte(s + "&"))
		} else {
			cancel()
		}
		return nil
	}

	go func() {
		sl.run(nil)
		signal <- struct{}{}
	}()

	select {
	case <-signal:
	case <-time.After(5 * time.Second):
		require.FailNow(t, "Scrape wasn't stopped.")
	}

	require.LessOrEqual(t, len(sl.cache.series), 2000, "More than 2000 series cached.")
}

func TestScrapeLoopAppend(t *testing.T) {
	tests := []struct {
		title           string
		honorLabels     bool
		scrapeLabels    string
		discoveryLabels []string
		expLset         labels.Labels
		expValue        float64
	}{
		{
			// When "honor_labels" is not set
			// label name collision is handler by adding a prefix.
			title:           "Label name collision",
			honorLabels:     false,
			scrapeLabels:    `metric{n="1"} 0`,
			discoveryLabels: []string{"n", "2"},
			expLset:         labels.FromStrings("__name__", "metric", "exported_n", "1", "n", "2"),
			expValue:        0,
		}, {
			// When "honor_labels" is not set
			// exported label from discovery don't get overwritten
			title:           "Label name collision",
			honorLabels:     false,
			scrapeLabels:    `metric 0`,
			discoveryLabels: []string{"n", "2", "exported_n", "2"},
			expLset:         labels.FromStrings("__name__", "metric", "n", "2", "exported_n", "2"),
			expValue:        0,
		}, {
			// Labels with no value need to be removed as these should not be ingested.
			title:           "Delete Empty labels",
			honorLabels:     false,
			scrapeLabels:    `metric{n=""} 0`,
			discoveryLabels: nil,
			expLset:         labels.FromStrings("__name__", "metric"),
			expValue:        0,
		}, {
			// Honor Labels should ignore labels with the same name.
			title:           "Honor Labels",
			honorLabels:     true,
			scrapeLabels:    `metric{n1="1", n2="2"} 0`,
			discoveryLabels: []string{"n1", "0"},
			expLset:         labels.FromStrings("__name__", "metric", "n1", "1", "n2", "2"),
			expValue:        0,
		}, {
			title:           "Stale - NaN",
			honorLabels:     false,
			scrapeLabels:    `metric NaN`,
			discoveryLabels: nil,
			expLset:         labels.FromStrings("__name__", "metric"),
			expValue:        math.Float64frombits(value.NormalNaN),
		},
	}

	for _, test := range tests {
		app := &collectResultAppender{}

		discoveryLabels := &Target{
			labels: labels.FromStrings(test.discoveryLabels...),
		}

		sl := newBasicScrapeLoop(t, context.Background(), nil, func(ctx context.Context) storage.Appender { return app }, 0)
		sl.sampleMutator = func(l labels.Labels) labels.Labels {
			return mutateSampleLabels(l, discoveryLabels, test.honorLabels, nil)
		}
		sl.reportSampleMutator = func(l labels.Labels) labels.Labels {
			return mutateReportSampleLabels(l, discoveryLabels)
		}

		now := time.Now()

		slApp := sl.appender(context.Background())
		_, _, _, err := sl.append(slApp, []byte(test.scrapeLabels), "text/plain", now)
		require.NoError(t, err)
		require.NoError(t, slApp.Commit())

		expected := []floatSample{
			{
				metric: test.expLset,
				t:      timestamp.FromTime(now),
				f:      test.expValue,
			},
		}

		t.Logf("Test:%s", test.title)
		requireEqual(t, expected, app.resultFloats)
	}
}

func requireEqual(t *testing.T, expected, actual interface{}, msgAndArgs ...interface{}) {
	testutil.RequireEqualWithOptions(t, expected, actual,
		[]cmp.Option{cmp.Comparer(equalFloatSamples), cmp.AllowUnexported(histogramSample{})},
		msgAndArgs...)
}

func TestScrapeLoopAppendForConflictingPrefixedLabels(t *testing.T) {
	testcases := map[string]struct {
		targetLabels  []string
		exposedLabels string
		expected      []string
	}{
		"One target label collides with existing label": {
			targetLabels:  []string{"foo", "2"},
			exposedLabels: `metric{foo="1"} 0`,
			expected:      []string{"__name__", "metric", "exported_foo", "1", "foo", "2"},
		},

		"One target label collides with existing label, plus target label already with prefix 'exported'": {
			targetLabels:  []string{"foo", "2", "exported_foo", "3"},
			exposedLabels: `metric{foo="1"} 0`,
			expected:      []string{"__name__", "metric", "exported_exported_foo", "1", "exported_foo", "3", "foo", "2"},
		},
		"One target label collides with existing label, plus existing label already with prefix 'exported": {
			targetLabels:  []string{"foo", "3"},
			exposedLabels: `metric{foo="1", exported_foo="2"} 0`,
			expected:      []string{"__name__", "metric", "exported_exported_foo", "1", "exported_foo", "2", "foo", "3"},
		},
		"One target label collides with existing label, both already with prefix 'exported'": {
			targetLabels:  []string{"exported_foo", "2"},
			exposedLabels: `metric{exported_foo="1"} 0`,
			expected:      []string{"__name__", "metric", "exported_exported_foo", "1", "exported_foo", "2"},
		},
		"Two target labels collide with existing labels, both with and without prefix 'exported'": {
			targetLabels:  []string{"foo", "3", "exported_foo", "4"},
			exposedLabels: `metric{foo="1", exported_foo="2"} 0`,
			expected: []string{
				"__name__", "metric", "exported_exported_foo", "1", "exported_exported_exported_foo",
				"2", "exported_foo", "4", "foo", "3",
			},
		},
		"Extreme example": {
			targetLabels:  []string{"foo", "0", "exported_exported_foo", "1", "exported_exported_exported_foo", "2"},
			exposedLabels: `metric{foo="3", exported_foo="4", exported_exported_exported_foo="5"} 0`,
			expected: []string{
				"__name__", "metric",
				"exported_exported_exported_exported_exported_foo", "5",
				"exported_exported_exported_exported_foo", "3",
				"exported_exported_exported_foo", "2",
				"exported_exported_foo", "1",
				"exported_foo", "4",
				"foo", "0",
			},
		},
	}

	for name, tc := range testcases {
		t.Run(name, func(t *testing.T) {
			app := &collectResultAppender{}
			sl := newBasicScrapeLoop(t, context.Background(), nil, func(ctx context.Context) storage.Appender { return app }, 0)
			sl.sampleMutator = func(l labels.Labels) labels.Labels {
				return mutateSampleLabels(l, &Target{labels: labels.FromStrings(tc.targetLabels...)}, false, nil)
			}
			slApp := sl.appender(context.Background())
			_, _, _, err := sl.append(slApp, []byte(tc.exposedLabels), "text/plain", time.Date(2000, 1, 1, 1, 0, 0, 0, time.UTC))
			require.NoError(t, err)

			require.NoError(t, slApp.Commit())

			requireEqual(t, []floatSample{
				{
					metric: labels.FromStrings(tc.expected...),
					t:      timestamp.FromTime(time.Date(2000, 1, 1, 1, 0, 0, 0, time.UTC)),
					f:      0,
				},
			}, app.resultFloats)
		})
	}
}

func TestScrapeLoopAppendCacheEntryButErrNotFound(t *testing.T) {
	// collectResultAppender's AddFast always returns ErrNotFound if we don't give it a next.
	app := &collectResultAppender{}
	sl := newBasicScrapeLoop(t, context.Background(), nil, func(ctx context.Context) storage.Appender { return app }, 0)

	fakeRef := storage.SeriesRef(1)
	expValue := float64(1)
	metric := []byte(`metric{n="1"} 1`)
	p, warning := textparse.New(metric, "text/plain", "", false, false, labels.NewSymbolTable())
	require.NotNil(t, p)
	require.NoError(t, warning)

	var lset labels.Labels
	p.Next()
	p.Metric(&lset)
	hash := lset.Hash()

	// Create a fake entry in the cache
	sl.cache.addRef(metric, fakeRef, lset, hash)
	now := time.Now()

	slApp := sl.appender(context.Background())
	_, _, _, err := sl.append(slApp, metric, "text/plain", now)
	require.NoError(t, err)
	require.NoError(t, slApp.Commit())

	expected := []floatSample{
		{
			metric: lset,
			t:      timestamp.FromTime(now),
			f:      expValue,
		},
	}

	require.Equal(t, expected, app.resultFloats)
}

func TestScrapeLoopAppendSampleLimit(t *testing.T) {
	resApp := &collectResultAppender{}
	app := &limitAppender{Appender: resApp, limit: 1}

	sl := newBasicScrapeLoop(t, context.Background(), nil, func(ctx context.Context) storage.Appender { return app }, 0)
	sl.sampleMutator = func(l labels.Labels) labels.Labels {
		if l.Has("deleteme") {
			return labels.EmptyLabels()
		}
		return l
	}
	sl.sampleLimit = app.limit

	// Get the value of the Counter before performing the append.
	beforeMetric := dto.Metric{}
	err := sl.metrics.targetScrapeSampleLimit.Write(&beforeMetric)
	require.NoError(t, err)

	beforeMetricValue := beforeMetric.GetCounter().GetValue()

	now := time.Now()
	slApp := sl.appender(context.Background())
	total, added, seriesAdded, err := sl.append(app, []byte("metric_a 1\nmetric_b 1\nmetric_c 1\n"), "text/plain", now)
	require.ErrorIs(t, err, errSampleLimit)
	require.NoError(t, slApp.Rollback())
	require.Equal(t, 3, total)
	require.Equal(t, 3, added)
	require.Equal(t, 1, seriesAdded)

	// Check that the Counter has been incremented a single time for the scrape,
	// not multiple times for each sample.
	metric := dto.Metric{}
	err = sl.metrics.targetScrapeSampleLimit.Write(&metric)
	require.NoError(t, err)

	value := metric.GetCounter().GetValue()
	change := value - beforeMetricValue
	require.Equal(t, 1.0, change, "Unexpected change of sample limit metric: %f", change)

	// And verify that we got the samples that fit under the limit.
	want := []floatSample{
		{
			metric: labels.FromStrings(model.MetricNameLabel, "metric_a"),
			t:      timestamp.FromTime(now),
			f:      1,
		},
	}
	requireEqual(t, want, resApp.rolledbackFloats, "Appended samples not as expected:\n%s", appender)

	now = time.Now()
	slApp = sl.appender(context.Background())
	total, added, seriesAdded, err = sl.append(slApp, []byte("metric_a 1\nmetric_b 1\nmetric_c{deleteme=\"yes\"} 1\nmetric_d 1\nmetric_e 1\nmetric_f 1\nmetric_g 1\nmetric_h{deleteme=\"yes\"} 1\nmetric_i{deleteme=\"yes\"} 1\n"), "text/plain", now)
	require.ErrorIs(t, err, errSampleLimit)
	require.NoError(t, slApp.Rollback())
	require.Equal(t, 9, total)
	require.Equal(t, 6, added)
	require.Equal(t, 0, seriesAdded)
}

func TestScrapeLoop_HistogramBucketLimit(t *testing.T) {
	resApp := &collectResultAppender{}
	app := &bucketLimitAppender{Appender: resApp, limit: 2}

	sl := newBasicScrapeLoop(t, context.Background(), nil, func(ctx context.Context) storage.Appender { return app }, 0)
	sl.enableNativeHistogramIngestion = true
	sl.sampleMutator = func(l labels.Labels) labels.Labels {
		if l.Has("deleteme") {
			return labels.EmptyLabels()
		}
		return l
	}
	sl.sampleLimit = app.limit

	metric := dto.Metric{}
	err := sl.metrics.targetScrapeNativeHistogramBucketLimit.Write(&metric)
	require.NoError(t, err)
	beforeMetricValue := metric.GetCounter().GetValue()

	nativeHistogram := prometheus.NewHistogramVec(
		prometheus.HistogramOpts{
			Namespace:                      "testing",
			Name:                           "example_native_histogram",
			Help:                           "This is used for testing",
			ConstLabels:                    map[string]string{"some": "value"},
			NativeHistogramBucketFactor:    1.1, // 10% increase from bucket to bucket
			NativeHistogramMaxBucketNumber: 100, // intentionally higher than the limit we'll use in the scraper
		},
		[]string{"size"},
	)
	registry := prometheus.NewRegistry()
	registry.Register(nativeHistogram)
	nativeHistogram.WithLabelValues("S").Observe(1.0)
	nativeHistogram.WithLabelValues("M").Observe(1.0)
	nativeHistogram.WithLabelValues("L").Observe(1.0)
	nativeHistogram.WithLabelValues("M").Observe(10.0)
	nativeHistogram.WithLabelValues("L").Observe(10.0) // in different bucket since > 1*1.1

	gathered, err := registry.Gather()
	require.NoError(t, err)
	require.NotEmpty(t, gathered)

	histogramMetricFamily := gathered[0]
	msg, err := MetricFamilyToProtobuf(histogramMetricFamily)
	require.NoError(t, err)

	now := time.Now()
	total, added, seriesAdded, err := sl.append(app, msg, "application/vnd.google.protobuf", now)
	require.NoError(t, err)
	require.Equal(t, 3, total)
	require.Equal(t, 3, added)
	require.Equal(t, 3, seriesAdded)

	err = sl.metrics.targetScrapeNativeHistogramBucketLimit.Write(&metric)
	require.NoError(t, err)
	metricValue := metric.GetCounter().GetValue()
	require.Equal(t, beforeMetricValue, metricValue)
	beforeMetricValue = metricValue

	nativeHistogram.WithLabelValues("L").Observe(100.0) // in different bucket since > 10*1.1

	gathered, err = registry.Gather()
	require.NoError(t, err)
	require.NotEmpty(t, gathered)

	histogramMetricFamily = gathered[0]
	msg, err = MetricFamilyToProtobuf(histogramMetricFamily)
	require.NoError(t, err)

	now = time.Now()
	total, added, seriesAdded, err = sl.append(app, msg, "application/vnd.google.protobuf", now)
	require.NoError(t, err)
	require.Equal(t, 3, total)
	require.Equal(t, 3, added)
	require.Equal(t, 3, seriesAdded)

	err = sl.metrics.targetScrapeNativeHistogramBucketLimit.Write(&metric)
	require.NoError(t, err)
	metricValue = metric.GetCounter().GetValue()
	require.Equal(t, beforeMetricValue, metricValue)
	beforeMetricValue = metricValue

	nativeHistogram.WithLabelValues("L").Observe(100000.0) // in different bucket since > 10*1.1

	gathered, err = registry.Gather()
	require.NoError(t, err)
	require.NotEmpty(t, gathered)

	histogramMetricFamily = gathered[0]
	msg, err = MetricFamilyToProtobuf(histogramMetricFamily)
	require.NoError(t, err)

	now = time.Now()
	total, added, seriesAdded, err = sl.append(app, msg, "application/vnd.google.protobuf", now)
	if !errors.Is(err, errBucketLimit) {
		t.Fatalf("Did not see expected histogram bucket limit error: %s", err)
	}
	require.NoError(t, app.Rollback())
	require.Equal(t, 3, total)
	require.Equal(t, 3, added)
	require.Equal(t, 0, seriesAdded)

	err = sl.metrics.targetScrapeNativeHistogramBucketLimit.Write(&metric)
	require.NoError(t, err)
	metricValue = metric.GetCounter().GetValue()
	require.Equal(t, beforeMetricValue+1, metricValue)
}

func TestScrapeLoop_ChangingMetricString(t *testing.T) {
	// This is a regression test for the scrape loop cache not properly maintaining
	// IDs when the string representation of a metric changes across a scrape. Thus
	// we use a real storage appender here.
	s := teststorage.New(t)
	defer s.Close()

	capp := &collectResultAppender{}
	sl := newBasicScrapeLoop(t, context.Background(), nil, func(ctx context.Context) storage.Appender { return capp }, 0)

	now := time.Now()
	slApp := sl.appender(context.Background())
	_, _, _, err := sl.append(slApp, []byte(`metric_a{a="1",b="1"} 1`), "text/plain", now)
	require.NoError(t, err)
	require.NoError(t, slApp.Commit())

	slApp = sl.appender(context.Background())
	_, _, _, err = sl.append(slApp, []byte(`metric_a{b="1",a="1"} 2`), "text/plain", now.Add(time.Minute))
	require.NoError(t, err)
	require.NoError(t, slApp.Commit())

	want := []floatSample{
		{
			metric: labels.FromStrings("__name__", "metric_a", "a", "1", "b", "1"),
			t:      timestamp.FromTime(now),
			f:      1,
		},
		{
			metric: labels.FromStrings("__name__", "metric_a", "a", "1", "b", "1"),
			t:      timestamp.FromTime(now.Add(time.Minute)),
			f:      2,
		},
	}
	require.Equal(t, want, capp.resultFloats, "Appended samples not as expected:\n%s", appender)
}

func TestScrapeLoopAppendFailsWithNoContentType(t *testing.T) {
	app := &collectResultAppender{}

	// Explicitly setting the lack of fallback protocol here to make it obvious.
	sl := newBasicScrapeLoopWithFallback(t, context.Background(), nil, func(ctx context.Context) storage.Appender { return app }, 0, "")

	now := time.Now()
	slApp := sl.appender(context.Background())
	_, _, _, err := sl.append(slApp, []byte("metric_a 1\n"), "", now)
	// We expect the appropriate error.
	require.ErrorContains(t, err, "non-compliant scrape target sending blank Content-Type and no fallback_scrape_protocol specified for target", "Expected \"non-compliant scrape\" error but got: %s", err)
}

func TestScrapeLoopAppendEmptyWithNoContentType(t *testing.T) {
	// This test ensures we there are no errors when we get a blank scrape or just want to append a stale marker.
	app := &collectResultAppender{}

	// Explicitly setting the lack of fallback protocol here to make it obvious.
	sl := newBasicScrapeLoopWithFallback(t, context.Background(), nil, func(ctx context.Context) storage.Appender { return app }, 0, "")

	now := time.Now()
	slApp := sl.appender(context.Background())
	_, _, _, err := sl.append(slApp, []byte(""), "", now)
	require.NoError(t, err)
	require.NoError(t, slApp.Commit())
}

func TestScrapeLoopAppendStaleness(t *testing.T) {
	app := &collectResultAppender{}

	sl := newBasicScrapeLoop(t, context.Background(), nil, func(ctx context.Context) storage.Appender { return app }, 0)

	now := time.Now()
	slApp := sl.appender(context.Background())
	_, _, _, err := sl.append(slApp, []byte("metric_a 1\n"), "text/plain", now)
	require.NoError(t, err)
	require.NoError(t, slApp.Commit())

	slApp = sl.appender(context.Background())
	_, _, _, err = sl.append(slApp, []byte(""), "", now.Add(time.Second))
	require.NoError(t, err)
	require.NoError(t, slApp.Commit())

	want := []floatSample{
		{
			metric: labels.FromStrings(model.MetricNameLabel, "metric_a"),
			t:      timestamp.FromTime(now),
			f:      1,
		},
		{
			metric: labels.FromStrings(model.MetricNameLabel, "metric_a"),
			t:      timestamp.FromTime(now.Add(time.Second)),
			f:      math.Float64frombits(value.StaleNaN),
		},
	}
	requireEqual(t, want, app.resultFloats, "Appended samples not as expected:\n%s", appender)
}

func TestScrapeLoopAppendNoStalenessIfTimestamp(t *testing.T) {
	app := &collectResultAppender{}
	sl := newBasicScrapeLoop(t, context.Background(), nil, func(ctx context.Context) storage.Appender { return app }, 0)
	now := time.Now()
	slApp := sl.appender(context.Background())
	_, _, _, err := sl.append(slApp, []byte("metric_a 1 1000\n"), "text/plain", now)
	require.NoError(t, err)
	require.NoError(t, slApp.Commit())

	slApp = sl.appender(context.Background())
	_, _, _, err = sl.append(slApp, []byte(""), "", now.Add(time.Second))
	require.NoError(t, err)
	require.NoError(t, slApp.Commit())

	want := []floatSample{
		{
			metric: labels.FromStrings(model.MetricNameLabel, "metric_a"),
			t:      1000,
			f:      1,
		},
	}
	require.Equal(t, want, app.resultFloats, "Appended samples not as expected:\n%s", appender)
}

func TestScrapeLoopAppendStalenessIfTrackTimestampStaleness(t *testing.T) {
	app := &collectResultAppender{}
	sl := newBasicScrapeLoop(t, context.Background(), nil, func(ctx context.Context) storage.Appender { return app }, 0)
	sl.trackTimestampsStaleness = true

	now := time.Now()
	slApp := sl.appender(context.Background())
	_, _, _, err := sl.append(slApp, []byte("metric_a 1 1000\n"), "text/plain", now)
	require.NoError(t, err)
	require.NoError(t, slApp.Commit())

	slApp = sl.appender(context.Background())
	_, _, _, err = sl.append(slApp, []byte(""), "", now.Add(time.Second))
	require.NoError(t, err)
	require.NoError(t, slApp.Commit())

	want := []floatSample{
		{
			metric: labels.FromStrings(model.MetricNameLabel, "metric_a"),
			t:      1000,
			f:      1,
		},
		{
			metric: labels.FromStrings(model.MetricNameLabel, "metric_a"),
			t:      timestamp.FromTime(now.Add(time.Second)),
			f:      math.Float64frombits(value.StaleNaN),
		},
	}
	requireEqual(t, want, app.resultFloats, "Appended samples not as expected:\n%s", appender)
}

func TestScrapeLoopAppendExemplar(t *testing.T) {
	tests := []struct {
		title                           string
		alwaysScrapeClassicHist         bool
		enableNativeHistogramsIngestion bool
		scrapeText                      string
		contentType                     string
		discoveryLabels                 []string
		floats                          []floatSample
		histograms                      []histogramSample
		exemplars                       []exemplar.Exemplar
	}{
		{
			title:           "Metric without exemplars",
			scrapeText:      "metric_total{n=\"1\"} 0\n# EOF",
			contentType:     "application/openmetrics-text",
			discoveryLabels: []string{"n", "2"},
			floats: []floatSample{{
				metric: labels.FromStrings("__name__", "metric_total", "exported_n", "1", "n", "2"),
				f:      0,
			}},
		},
		{
			title:           "Metric with exemplars",
			scrapeText:      "metric_total{n=\"1\"} 0 # {a=\"abc\"} 1.0\n# EOF",
			contentType:     "application/openmetrics-text",
			discoveryLabels: []string{"n", "2"},
			floats: []floatSample{{
				metric: labels.FromStrings("__name__", "metric_total", "exported_n", "1", "n", "2"),
				f:      0,
			}},
			exemplars: []exemplar.Exemplar{
				{Labels: labels.FromStrings("a", "abc"), Value: 1},
			},
		},
		{
			title:           "Metric with exemplars and TS",
			scrapeText:      "metric_total{n=\"1\"} 0 # {a=\"abc\"} 1.0 10000\n# EOF",
			contentType:     "application/openmetrics-text",
			discoveryLabels: []string{"n", "2"},
			floats: []floatSample{{
				metric: labels.FromStrings("__name__", "metric_total", "exported_n", "1", "n", "2"),
				f:      0,
			}},
			exemplars: []exemplar.Exemplar{
				{Labels: labels.FromStrings("a", "abc"), Value: 1, Ts: 10000000, HasTs: true},
			},
		},
		{
			title: "Two metrics and exemplars",
			scrapeText: `metric_total{n="1"} 1 # {t="1"} 1.0 10000
metric_total{n="2"} 2 # {t="2"} 2.0 20000
# EOF`,
			contentType: "application/openmetrics-text",
			floats: []floatSample{{
				metric: labels.FromStrings("__name__", "metric_total", "n", "1"),
				f:      1,
			}, {
				metric: labels.FromStrings("__name__", "metric_total", "n", "2"),
				f:      2,
			}},
			exemplars: []exemplar.Exemplar{
				{Labels: labels.FromStrings("t", "1"), Value: 1, Ts: 10000000, HasTs: true},
				{Labels: labels.FromStrings("t", "2"), Value: 2, Ts: 20000000, HasTs: true},
			},
		},
		{
			title: "Native histogram with three exemplars",

			enableNativeHistogramsIngestion: true,
			scrapeText: `name: "test_histogram"
help: "Test histogram with many buckets removed to keep it manageable in size."
type: HISTOGRAM
metric: <
  histogram: <
    sample_count: 175
    sample_sum: 0.0008280461746287094
    bucket: <
      cumulative_count: 2
      upper_bound: -0.0004899999999999998
    >
    bucket: <
      cumulative_count: 4
      upper_bound: -0.0003899999999999998
      exemplar: <
        label: <
          name: "dummyID"
          value: "59727"
        >
        value: -0.00039
        timestamp: <
          seconds: 1625851155
          nanos: 146848499
        >
      >
    >
    bucket: <
      cumulative_count: 16
      upper_bound: -0.0002899999999999998
      exemplar: <
        label: <
          name: "dummyID"
          value: "5617"
        >
        value: -0.00029
      >
    >
    bucket: <
      cumulative_count: 32
      upper_bound: -0.0001899999999999998
      exemplar: <
        label: <
          name: "dummyID"
          value: "58215"
        >
        value: -0.00019
        timestamp: <
          seconds: 1625851055
          nanos: 146848599
        >
      >
    >
    schema: 3
    zero_threshold: 2.938735877055719e-39
    zero_count: 2
    negative_span: <
      offset: -162
      length: 1
    >
    negative_span: <
      offset: 23
      length: 4
    >
    negative_delta: 1
    negative_delta: 3
    negative_delta: -2
    negative_delta: -1
    negative_delta: 1
    positive_span: <
      offset: -161
      length: 1
    >
    positive_span: <
      offset: 8
      length: 3
    >
    positive_delta: 1
    positive_delta: 2
    positive_delta: -1
    positive_delta: -1
  >
  timestamp_ms: 1234568
>

`,
			contentType: "application/vnd.google.protobuf",
			histograms: []histogramSample{{
				t:      1234568,
				metric: labels.FromStrings("__name__", "test_histogram"),
				h: &histogram.Histogram{
					Count:         175,
					ZeroCount:     2,
					Sum:           0.0008280461746287094,
					ZeroThreshold: 2.938735877055719e-39,
					Schema:        3,
					PositiveSpans: []histogram.Span{
						{Offset: -161, Length: 1},
						{Offset: 8, Length: 3},
					},
					NegativeSpans: []histogram.Span{
						{Offset: -162, Length: 1},
						{Offset: 23, Length: 4},
					},
					PositiveBuckets: []int64{1, 2, -1, -1},
					NegativeBuckets: []int64{1, 3, -2, -1, 1},
				},
			}},
			exemplars: []exemplar.Exemplar{
				// Native histogram exemplars are arranged by timestamp, and those with missing timestamps are dropped.
				{Labels: labels.FromStrings("dummyID", "58215"), Value: -0.00019, Ts: 1625851055146, HasTs: true},
				{Labels: labels.FromStrings("dummyID", "59727"), Value: -0.00039, Ts: 1625851155146, HasTs: true},
			},
		},
		{
			title: "Native histogram with three exemplars scraped as classic histogram",

			enableNativeHistogramsIngestion: true,
			scrapeText: `name: "test_histogram"
help: "Test histogram with many buckets removed to keep it manageable in size."
type: HISTOGRAM
metric: <
  histogram: <
    sample_count: 175
    sample_sum: 0.0008280461746287094
    bucket: <
      cumulative_count: 2
      upper_bound: -0.0004899999999999998
    >
    bucket: <
      cumulative_count: 4
      upper_bound: -0.0003899999999999998
      exemplar: <
        label: <
          name: "dummyID"
          value: "59727"
        >
        value: -0.00039
        timestamp: <
          seconds: 1625851155
          nanos: 146848499
        >
      >
    >
    bucket: <
      cumulative_count: 16
      upper_bound: -0.0002899999999999998
      exemplar: <
        label: <
          name: "dummyID"
          value: "5617"
        >
        value: -0.00029
      >
    >
    bucket: <
      cumulative_count: 32
      upper_bound: -0.0001899999999999998
      exemplar: <
        label: <
          name: "dummyID"
          value: "58215"
        >
        value: -0.00019
        timestamp: <
          seconds: 1625851055
          nanos: 146848599
        >
      >
    >
    schema: 3
    zero_threshold: 2.938735877055719e-39
    zero_count: 2
    negative_span: <
      offset: -162
      length: 1
    >
    negative_span: <
      offset: 23
      length: 4
    >
    negative_delta: 1
    negative_delta: 3
    negative_delta: -2
    negative_delta: -1
    negative_delta: 1
    positive_span: <
      offset: -161
      length: 1
    >
    positive_span: <
      offset: 8
      length: 3
    >
    positive_delta: 1
    positive_delta: 2
    positive_delta: -1
    positive_delta: -1
  >
  timestamp_ms: 1234568
>

`,
			alwaysScrapeClassicHist: true,
			contentType:             "application/vnd.google.protobuf",
			floats: []floatSample{
				{metric: labels.FromStrings("__name__", "test_histogram_count"), t: 1234568, f: 175},
				{metric: labels.FromStrings("__name__", "test_histogram_sum"), t: 1234568, f: 0.0008280461746287094},
				{metric: labels.FromStrings("__name__", "test_histogram_bucket", "le", "-0.0004899999999999998"), t: 1234568, f: 2},
				{metric: labels.FromStrings("__name__", "test_histogram_bucket", "le", "-0.0003899999999999998"), t: 1234568, f: 4},
				{metric: labels.FromStrings("__name__", "test_histogram_bucket", "le", "-0.0002899999999999998"), t: 1234568, f: 16},
				{metric: labels.FromStrings("__name__", "test_histogram_bucket", "le", "-0.0001899999999999998"), t: 1234568, f: 32},
				{metric: labels.FromStrings("__name__", "test_histogram_bucket", "le", "+Inf"), t: 1234568, f: 175},
			},
			histograms: []histogramSample{{
				t:      1234568,
				metric: labels.FromStrings("__name__", "test_histogram"),
				h: &histogram.Histogram{
					Count:         175,
					ZeroCount:     2,
					Sum:           0.0008280461746287094,
					ZeroThreshold: 2.938735877055719e-39,
					Schema:        3,
					PositiveSpans: []histogram.Span{
						{Offset: -161, Length: 1},
						{Offset: 8, Length: 3},
					},
					NegativeSpans: []histogram.Span{
						{Offset: -162, Length: 1},
						{Offset: 23, Length: 4},
					},
					PositiveBuckets: []int64{1, 2, -1, -1},
					NegativeBuckets: []int64{1, 3, -2, -1, 1},
				},
			}},
			exemplars: []exemplar.Exemplar{
				// Native histogram one is arranged by timestamp.
				// Exemplars with missing timestamps are dropped for native histograms.
				{Labels: labels.FromStrings("dummyID", "58215"), Value: -0.00019, Ts: 1625851055146, HasTs: true},
				{Labels: labels.FromStrings("dummyID", "59727"), Value: -0.00039, Ts: 1625851155146, HasTs: true},
				// Classic histogram one is in order of appearance.
				// Exemplars with missing timestamps are supported for classic histograms.
				{Labels: labels.FromStrings("dummyID", "59727"), Value: -0.00039, Ts: 1625851155146, HasTs: true},
				{Labels: labels.FromStrings("dummyID", "5617"), Value: -0.00029, Ts: 1234568, HasTs: false},
				{Labels: labels.FromStrings("dummyID", "58215"), Value: -0.00019, Ts: 1625851055146, HasTs: true},
			},
		},
	}

	for _, test := range tests {
		t.Run(test.title, func(t *testing.T) {
			app := &collectResultAppender{}

			discoveryLabels := &Target{
				labels: labels.FromStrings(test.discoveryLabels...),
			}

			sl := newBasicScrapeLoop(t, context.Background(), nil, func(ctx context.Context) storage.Appender { return app }, 0)
			sl.enableNativeHistogramIngestion = test.enableNativeHistogramsIngestion
			sl.sampleMutator = func(l labels.Labels) labels.Labels {
				return mutateSampleLabels(l, discoveryLabels, false, nil)
			}
			sl.reportSampleMutator = func(l labels.Labels) labels.Labels {
				return mutateReportSampleLabels(l, discoveryLabels)
			}
			sl.alwaysScrapeClassicHist = test.alwaysScrapeClassicHist

			now := time.Now()

			for i := range test.floats {
				if test.floats[i].t != 0 {
					continue
				}
				test.floats[i].t = timestamp.FromTime(now)
			}

			// We need to set the timestamp for expected exemplars that does not have a timestamp.
			for i := range test.exemplars {
				if test.exemplars[i].Ts == 0 {
					test.exemplars[i].Ts = timestamp.FromTime(now)
				}
			}

			buf := &bytes.Buffer{}
			if test.contentType == "application/vnd.google.protobuf" {
				require.NoError(t, textToProto(test.scrapeText, buf))
			} else {
				buf.WriteString(test.scrapeText)
			}

			_, _, _, err := sl.append(app, buf.Bytes(), test.contentType, now)
			require.NoError(t, err)
			require.NoError(t, app.Commit())
			requireEqual(t, test.floats, app.resultFloats)
			requireEqual(t, test.histograms, app.resultHistograms)
			requireEqual(t, test.exemplars, app.resultExemplars)
		})
	}
}

func textToProto(text string, buf *bytes.Buffer) error {
	// In case of protobuf, we have to create the binary representation.
	pb := &dto.MetricFamily{}
	// From text to proto message.
	err := proto.UnmarshalText(text, pb)
	if err != nil {
		return err
	}
	// From proto message to binary protobuf.
	protoBuf, err := proto.Marshal(pb)
	if err != nil {
		return err
	}
	// Write first length, then binary protobuf.
	varintBuf := binary.AppendUvarint(nil, uint64(len(protoBuf)))
	buf.Write(varintBuf)
	buf.Write(protoBuf)
	return nil
}

func TestScrapeLoopAppendExemplarSeries(t *testing.T) {
	scrapeText := []string{`metric_total{n="1"} 1 # {t="1"} 1.0 10000
# EOF`, `metric_total{n="1"} 2 # {t="2"} 2.0 20000
# EOF`}
	samples := []floatSample{{
		metric: labels.FromStrings("__name__", "metric_total", "n", "1"),
		f:      1,
	}, {
		metric: labels.FromStrings("__name__", "metric_total", "n", "1"),
		f:      2,
	}}
	exemplars := []exemplar.Exemplar{
		{Labels: labels.FromStrings("t", "1"), Value: 1, Ts: 10000000, HasTs: true},
		{Labels: labels.FromStrings("t", "2"), Value: 2, Ts: 20000000, HasTs: true},
	}
	discoveryLabels := &Target{
		labels: labels.FromStrings(),
	}

	app := &collectResultAppender{}

	sl := newBasicScrapeLoop(t, context.Background(), nil, func(ctx context.Context) storage.Appender { return app }, 0)
	sl.sampleMutator = func(l labels.Labels) labels.Labels {
		return mutateSampleLabels(l, discoveryLabels, false, nil)
	}
	sl.reportSampleMutator = func(l labels.Labels) labels.Labels {
		return mutateReportSampleLabels(l, discoveryLabels)
	}

	now := time.Now()

	for i := range samples {
		ts := now.Add(time.Second * time.Duration(i))
		samples[i].t = timestamp.FromTime(ts)
	}

	// We need to set the timestamp for expected exemplars that does not have a timestamp.
	for i := range exemplars {
		if exemplars[i].Ts == 0 {
			ts := now.Add(time.Second * time.Duration(i))
			exemplars[i].Ts = timestamp.FromTime(ts)
		}
	}

	for i, st := range scrapeText {
		_, _, _, err := sl.append(app, []byte(st), "application/openmetrics-text", timestamp.Time(samples[i].t))
		require.NoError(t, err)
		require.NoError(t, app.Commit())
	}

	requireEqual(t, samples, app.resultFloats)
	requireEqual(t, exemplars, app.resultExemplars)
}

func TestScrapeLoopRunReportsTargetDownOnScrapeError(t *testing.T) {
	var (
		scraper  = &testScraper{}
		appender = &collectResultAppender{}
		app      = func(ctx context.Context) storage.Appender { return appender }
	)

	ctx, cancel := context.WithCancel(context.Background())
	sl := newBasicScrapeLoop(t, ctx, scraper, app, 10*time.Millisecond)

	scraper.scrapeFunc = func(ctx context.Context, w io.Writer) error {
		cancel()
		return errors.New("scrape failed")
	}

	sl.run(nil)
	require.Equal(t, 0.0, appender.resultFloats[0].f, "bad 'up' value")
}

func TestScrapeLoopRunReportsTargetDownOnInvalidUTF8(t *testing.T) {
	var (
		scraper  = &testScraper{}
		appender = &collectResultAppender{}
		app      = func(ctx context.Context) storage.Appender { return appender }
	)

	ctx, cancel := context.WithCancel(context.Background())
	sl := newBasicScrapeLoop(t, ctx, scraper, app, 10*time.Millisecond)

	scraper.scrapeFunc = func(ctx context.Context, w io.Writer) error {
		cancel()
		w.Write([]byte("a{l=\"\xff\"} 1\n"))
		return nil
	}

	sl.run(nil)
	require.Equal(t, 0.0, appender.resultFloats[0].f, "bad 'up' value")
}

type errorAppender struct {
	collectResultAppender
}

func (app *errorAppender) Append(ref storage.SeriesRef, lset labels.Labels, t int64, v float64) (storage.SeriesRef, error) {
	switch lset.Get(model.MetricNameLabel) {
	case "out_of_order":
		return 0, storage.ErrOutOfOrderSample
	case "amend":
		return 0, storage.ErrDuplicateSampleForTimestamp
	case "out_of_bounds":
		return 0, storage.ErrOutOfBounds
	default:
		return app.collectResultAppender.Append(ref, lset, t, v)
	}
}

func TestScrapeLoopAppendGracefullyIfAmendOrOutOfOrderOrOutOfBounds(t *testing.T) {
	app := &errorAppender{}
	sl := newBasicScrapeLoop(t, context.Background(), nil, func(ctx context.Context) storage.Appender { return app }, 0)

	now := time.Unix(1, 0)
	slApp := sl.appender(context.Background())
	total, added, seriesAdded, err := sl.append(slApp, []byte("out_of_order 1\namend 1\nnormal 1\nout_of_bounds 1\n"), "text/plain", now)
	require.NoError(t, err)
	require.NoError(t, slApp.Commit())

	want := []floatSample{
		{
			metric: labels.FromStrings(model.MetricNameLabel, "normal"),
			t:      timestamp.FromTime(now),
			f:      1,
		},
	}
	requireEqual(t, want, app.resultFloats, "Appended samples not as expected:\n%s", appender)
	require.Equal(t, 4, total)
	require.Equal(t, 4, added)
	require.Equal(t, 1, seriesAdded)
}

func TestScrapeLoopOutOfBoundsTimeError(t *testing.T) {
	app := &collectResultAppender{}
	sl := newBasicScrapeLoop(t, context.Background(), nil,
		func(ctx context.Context) storage.Appender {
			return &timeLimitAppender{
				Appender: app,
				maxTime:  timestamp.FromTime(time.Now().Add(10 * time.Minute)),
			}
		},
		0,
	)

	now := time.Now().Add(20 * time.Minute)
	slApp := sl.appender(context.Background())
	total, added, seriesAdded, err := sl.append(slApp, []byte("normal 1\n"), "text/plain", now)
	require.NoError(t, err)
	require.NoError(t, slApp.Commit())
	require.Equal(t, 1, total)
	require.Equal(t, 1, added)
	require.Equal(t, 0, seriesAdded)
}

func TestTargetScraperScrapeOK(t *testing.T) {
	const (
		configTimeout   = 1500 * time.Millisecond
		expectedTimeout = "1.5"
	)

	var (
		protobufParsing bool
		allowUTF8       bool
		qValuePattern   = regexp.MustCompile(`q=([0-9]+(\.\d+)?)`)
	)

	server := httptest.NewServer(
		http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			accept := r.Header.Get("Accept")
			if allowUTF8 {
				require.Containsf(t, accept, "escaping=allow-utf-8", "Expected Accept header to allow utf8, got %q", accept)
			}
			if protobufParsing {
				require.True(t, strings.HasPrefix(accept, "application/vnd.google.protobuf;"),
					"Expected Accept header to prefer application/vnd.google.protobuf.")
			}

			contentTypes := strings.Split(accept, ",")
			for _, ct := range contentTypes {
				match := qValuePattern.FindStringSubmatch(ct)
				require.Len(t, match, 3)
				qValue, err := strconv.ParseFloat(match[1], 64)
				require.NoError(t, err, "Error parsing q value")
				require.GreaterOrEqual(t, qValue, float64(0))
				require.LessOrEqual(t, qValue, float64(1))
				require.LessOrEqual(t, len(strings.Split(match[1], ".")[1]), 3, "q value should have at most 3 decimal places")
			}

			timeout := r.Header.Get("X-Prometheus-Scrape-Timeout-Seconds")
			require.Equal(t, expectedTimeout, timeout, "Expected scrape timeout header.")

			if allowUTF8 {
				w.Header().Set("Content-Type", `text/plain; version=1.0.0; escaping=allow-utf-8`)
			} else {
				w.Header().Set("Content-Type", `text/plain; version=0.0.4`)
			}
			w.Write([]byte("metric_a 1\nmetric_b 2\n"))
		}),
	)
	defer server.Close()

	serverURL, err := url.Parse(server.URL)
	if err != nil {
		panic(err)
	}

	runTest := func(acceptHeader string) {
		ts := &targetScraper{
			Target: &Target{
				labels: labels.FromStrings(
					model.SchemeLabel, serverURL.Scheme,
					model.AddressLabel, serverURL.Host,
				),
				scrapeConfig: &config.ScrapeConfig{},
			},
			client:       http.DefaultClient,
			timeout:      configTimeout,
			acceptHeader: acceptHeader,
		}
		var buf bytes.Buffer

		resp, err := ts.scrape(context.Background())
		require.NoError(t, err)
		contentType, err := ts.readResponse(context.Background(), resp, &buf)
		require.NoError(t, err)
		if allowUTF8 {
			require.Equal(t, "text/plain; version=1.0.0; escaping=allow-utf-8", contentType)
		} else {
			require.Equal(t, "text/plain; version=0.0.4", contentType)
		}
		require.Equal(t, "metric_a 1\nmetric_b 2\n", buf.String())
	}

	runTest(acceptHeader(config.DefaultScrapeProtocols, model.LegacyValidation))
	protobufParsing = true
	runTest(acceptHeader(config.DefaultProtoFirstScrapeProtocols, model.LegacyValidation))
	protobufParsing = false
	allowUTF8 = true
	runTest(acceptHeader(config.DefaultScrapeProtocols, model.UTF8Validation))
	protobufParsing = true
	runTest(acceptHeader(config.DefaultProtoFirstScrapeProtocols, model.UTF8Validation))
}

func TestTargetScrapeScrapeCancel(t *testing.T) {
	block := make(chan struct{})

	server := httptest.NewServer(
		http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			<-block
		}),
	)
	defer server.Close()

	serverURL, err := url.Parse(server.URL)
	if err != nil {
		panic(err)
	}

	ts := &targetScraper{
		Target: &Target{
			labels: labels.FromStrings(
				model.SchemeLabel, serverURL.Scheme,
				model.AddressLabel, serverURL.Host,
			),
			scrapeConfig: &config.ScrapeConfig{},
		},
		client:       http.DefaultClient,
		acceptHeader: acceptHeader(config.DefaultGlobalConfig.ScrapeProtocols, model.LegacyValidation),
	}
	ctx, cancel := context.WithCancel(context.Background())

	errc := make(chan error, 1)

	go func() {
		time.Sleep(1 * time.Second)
		cancel()
	}()

	go func() {
		_, err := ts.scrape(ctx)
		switch {
		case err == nil:
			errc <- errors.New("Expected error but got nil")
		case !errors.Is(ctx.Err(), context.Canceled):
			errc <- fmt.Errorf("Expected context cancellation error but got: %w", ctx.Err())
		default:
			close(errc)
		}
	}()

	select {
	case <-time.After(5 * time.Second):
		require.FailNow(t, "Scrape function did not return unexpectedly.")
	case err := <-errc:
		require.NoError(t, err)
	}
	// If this is closed in a defer above the function the test server
	// doesn't terminate and the test doesn't complete.
	close(block)
}

func TestTargetScrapeScrapeNotFound(t *testing.T) {
	server := httptest.NewServer(
		http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			w.WriteHeader(http.StatusNotFound)
		}),
	)
	defer server.Close()

	serverURL, err := url.Parse(server.URL)
	if err != nil {
		panic(err)
	}

	ts := &targetScraper{
		Target: &Target{
			labels: labels.FromStrings(
				model.SchemeLabel, serverURL.Scheme,
				model.AddressLabel, serverURL.Host,
			),
			scrapeConfig: &config.ScrapeConfig{},
		},
		client:       http.DefaultClient,
		acceptHeader: acceptHeader(config.DefaultGlobalConfig.ScrapeProtocols, model.LegacyValidation),
	}

	resp, err := ts.scrape(context.Background())
	require.NoError(t, err)
	_, err = ts.readResponse(context.Background(), resp, io.Discard)
	require.ErrorContains(t, err, "404", "Expected \"404 NotFound\" error but got: %s", err)
}

func TestTargetScraperBodySizeLimit(t *testing.T) {
	const (
		bodySizeLimit = 15
		responseBody  = "metric_a 1\nmetric_b 2\n"
	)
	var gzipResponse bool
	server := httptest.NewServer(
		http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			w.Header().Set("Content-Type", `text/plain; version=0.0.4`)
			if gzipResponse {
				w.Header().Set("Content-Encoding", "gzip")
				gw := gzip.NewWriter(w)
				defer gw.Close()
				gw.Write([]byte(responseBody))
				return
			}
			w.Write([]byte(responseBody))
		}),
	)
	defer server.Close()

	serverURL, err := url.Parse(server.URL)
	if err != nil {
		panic(err)
	}

	ts := &targetScraper{
		Target: &Target{
			labels: labels.FromStrings(
				model.SchemeLabel, serverURL.Scheme,
				model.AddressLabel, serverURL.Host,
			),
			scrapeConfig: &config.ScrapeConfig{},
		},
		client:        http.DefaultClient,
		bodySizeLimit: bodySizeLimit,
		acceptHeader:  acceptHeader(config.DefaultGlobalConfig.ScrapeProtocols, model.LegacyValidation),
		metrics:       newTestScrapeMetrics(t),
	}
	var buf bytes.Buffer

	// Target response uncompressed body, scrape with body size limit.
	resp, err := ts.scrape(context.Background())
	require.NoError(t, err)
	_, err = ts.readResponse(context.Background(), resp, &buf)
	require.ErrorIs(t, err, errBodySizeLimit)
	require.Equal(t, bodySizeLimit, buf.Len())
	// Target response gzip compressed body, scrape with body size limit.
	gzipResponse = true
	buf.Reset()
	resp, err = ts.scrape(context.Background())
	require.NoError(t, err)
	_, err = ts.readResponse(context.Background(), resp, &buf)
	require.ErrorIs(t, err, errBodySizeLimit)
	require.Equal(t, bodySizeLimit, buf.Len())
	// Target response uncompressed body, scrape without body size limit.
	gzipResponse = false
	buf.Reset()
	ts.bodySizeLimit = 0
	resp, err = ts.scrape(context.Background())
	require.NoError(t, err)
	_, err = ts.readResponse(context.Background(), resp, &buf)
	require.NoError(t, err)
	require.Len(t, responseBody, buf.Len())
	// Target response gzip compressed body, scrape without body size limit.
	gzipResponse = true
	buf.Reset()
	resp, err = ts.scrape(context.Background())
	require.NoError(t, err)
	_, err = ts.readResponse(context.Background(), resp, &buf)
	require.NoError(t, err)
	require.Len(t, responseBody, buf.Len())
}

// testScraper implements the scraper interface and allows setting values
// returned by its methods. It also allows setting a custom scrape function.
type testScraper struct {
	offsetDur time.Duration

	lastStart    time.Time
	lastDuration time.Duration
	lastError    error

	scrapeErr  error
	scrapeFunc func(context.Context, io.Writer) error
}

func (ts *testScraper) offset(time.Duration, uint64) time.Duration {
	return ts.offsetDur
}

func (ts *testScraper) Report(start time.Time, duration time.Duration, err error) {
	ts.lastStart = start
	ts.lastDuration = duration
	ts.lastError = err
}

func (ts *testScraper) scrape(ctx context.Context) (*http.Response, error) {
	return nil, ts.scrapeErr
}

func (ts *testScraper) readResponse(ctx context.Context, resp *http.Response, w io.Writer) (string, error) {
	if ts.scrapeFunc != nil {
		return "", ts.scrapeFunc(ctx, w)
	}
	return "", ts.scrapeErr
}

func TestScrapeLoop_RespectTimestamps(t *testing.T) {
	s := teststorage.New(t)
	defer s.Close()

	app := s.Appender(context.Background())
	capp := &collectResultAppender{next: app}
	sl := newBasicScrapeLoop(t, context.Background(), nil, func(ctx context.Context) storage.Appender { return capp }, 0)

	now := time.Now()
	slApp := sl.appender(context.Background())
	_, _, _, err := sl.append(slApp, []byte(`metric_a{a="1",b="1"} 1 0`), "text/plain", now)
	require.NoError(t, err)
	require.NoError(t, slApp.Commit())

	want := []floatSample{
		{
			metric: labels.FromStrings("__name__", "metric_a", "a", "1", "b", "1"),
			t:      0,
			f:      1,
		},
	}
	require.Equal(t, want, capp.resultFloats, "Appended samples not as expected:\n%s", appender)
}

func TestScrapeLoop_DiscardTimestamps(t *testing.T) {
	s := teststorage.New(t)
	defer s.Close()

	app := s.Appender(context.Background())

	capp := &collectResultAppender{next: app}

	sl := newBasicScrapeLoop(t, context.Background(), nil, func(ctx context.Context) storage.Appender { return capp }, 0)
	sl.honorTimestamps = false

	now := time.Now()
	slApp := sl.appender(context.Background())
	_, _, _, err := sl.append(slApp, []byte(`metric_a{a="1",b="1"} 1 0`), "text/plain", now)
	require.NoError(t, err)
	require.NoError(t, slApp.Commit())

	want := []floatSample{
		{
			metric: labels.FromStrings("__name__", "metric_a", "a", "1", "b", "1"),
			t:      timestamp.FromTime(now),
			f:      1,
		},
	}
	require.Equal(t, want, capp.resultFloats, "Appended samples not as expected:\n%s", appender)
}

func TestScrapeLoopDiscardDuplicateLabels(t *testing.T) {
	s := teststorage.New(t)
	defer s.Close()

	ctx, cancel := context.WithCancel(context.Background())
	sl := newBasicScrapeLoop(t, ctx, &testScraper{}, s.Appender, 0)
	defer cancel()

	// We add a good and a bad metric to check that both are discarded.
	slApp := sl.appender(ctx)
	_, _, _, err := sl.append(slApp, []byte("test_metric{le=\"500\"} 1\ntest_metric{le=\"600\",le=\"700\"} 1\n"), "text/plain", time.Time{})
	require.Error(t, err)
	require.NoError(t, slApp.Rollback())
	// We need to cycle staleness cache maps after a manual rollback. Otherwise they will have old entries in them,
	// which would cause ErrDuplicateSampleForTimestamp errors on the next append.
	sl.cache.iterDone(true)

	q, err := s.Querier(time.Time{}.UnixNano(), 0)
	require.NoError(t, err)
	series := q.Select(ctx, false, nil, labels.MustNewMatcher(labels.MatchRegexp, "__name__", ".*"))
	require.False(t, series.Next(), "series found in tsdb")
	require.NoError(t, series.Err())

	// We add a good metric to check that it is recorded.
	slApp = sl.appender(ctx)
	_, _, _, err = sl.append(slApp, []byte("test_metric{le=\"500\"} 1\n"), "text/plain", time.Time{})
	require.NoError(t, err)
	require.NoError(t, slApp.Commit())

	q, err = s.Querier(time.Time{}.UnixNano(), 0)
	require.NoError(t, err)
	series = q.Select(ctx, false, nil, labels.MustNewMatcher(labels.MatchEqual, "le", "500"))
	require.True(t, series.Next(), "series not found in tsdb")
	require.NoError(t, series.Err())
	require.False(t, series.Next(), "more than one series found in tsdb")
}

func TestScrapeLoopDiscardUnnamedMetrics(t *testing.T) {
	s := teststorage.New(t)
	defer s.Close()

	app := s.Appender(context.Background())

	ctx, cancel := context.WithCancel(context.Background())
	sl := newBasicScrapeLoop(t, context.Background(), &testScraper{}, func(ctx context.Context) storage.Appender { return app }, 0)
	sl.sampleMutator = func(l labels.Labels) labels.Labels {
		if l.Has("drop") {
			return labels.FromStrings("no", "name") // This label set will trigger an error.
		}
		return l
	}
	defer cancel()

	slApp := sl.appender(context.Background())
	_, _, _, err := sl.append(slApp, []byte("nok 1\nnok2{drop=\"drop\"} 1\n"), "text/plain", time.Time{})
	require.Error(t, err)
	require.NoError(t, slApp.Rollback())
	require.Equal(t, errNameLabelMandatory, err)

	q, err := s.Querier(time.Time{}.UnixNano(), 0)
	require.NoError(t, err)
	series := q.Select(ctx, false, nil, labels.MustNewMatcher(labels.MatchRegexp, "__name__", ".*"))
	require.False(t, series.Next(), "series found in tsdb")
	require.NoError(t, series.Err())
}

func TestReusableConfig(t *testing.T) {
	variants := []*config.ScrapeConfig{
		{
			JobName:       "prometheus",
			ScrapeTimeout: model.Duration(15 * time.Second),
		},
		{
			JobName:       "httpd",
			ScrapeTimeout: model.Duration(15 * time.Second),
		},
		{
			JobName:       "prometheus",
			ScrapeTimeout: model.Duration(5 * time.Second),
		},
		{
			JobName:     "prometheus",
			MetricsPath: "/metrics",
		},
		{
			JobName:     "prometheus",
			MetricsPath: "/metrics2",
		},
		{
			JobName:       "prometheus",
			ScrapeTimeout: model.Duration(5 * time.Second),
			MetricsPath:   "/metrics2",
		},
		{
			JobName:        "prometheus",
			ScrapeInterval: model.Duration(5 * time.Second),
			MetricsPath:    "/metrics2",
		},
		{
			JobName:        "prometheus",
			ScrapeInterval: model.Duration(5 * time.Second),
			SampleLimit:    1000,
			MetricsPath:    "/metrics2",
		},
	}

	match := [][]int{
		{0, 2},
		{4, 5},
		{4, 6},
		{4, 7},
		{5, 6},
		{5, 7},
		{6, 7},
	}
	noMatch := [][]int{
		{1, 2},
		{0, 4},
		{3, 4},
	}

	for i, m := range match {
		require.True(t, reusableCache(variants[m[0]], variants[m[1]]), "match test %d", i)
		require.True(t, reusableCache(variants[m[1]], variants[m[0]]), "match test %d", i)
		require.True(t, reusableCache(variants[m[1]], variants[m[1]]), "match test %d", i)
		require.True(t, reusableCache(variants[m[0]], variants[m[0]]), "match test %d", i)
	}
	for i, m := range noMatch {
		require.False(t, reusableCache(variants[m[0]], variants[m[1]]), "not match test %d", i)
		require.False(t, reusableCache(variants[m[1]], variants[m[0]]), "not match test %d", i)
	}
}

func TestReuseScrapeCache(t *testing.T) {
	var (
		app = &nopAppendable{}
		cfg = &config.ScrapeConfig{
			JobName:        "Prometheus",
			ScrapeTimeout:  model.Duration(5 * time.Second),
			ScrapeInterval: model.Duration(5 * time.Second),
			MetricsPath:    "/metrics",
		}
		sp, _ = newScrapePool(cfg, app, 0, nil, nil, &Options{}, newTestScrapeMetrics(t))
		t1    = &Target{
			labels:       labels.FromStrings("labelNew", "nameNew", "labelNew1", "nameNew1", "labelNew2", "nameNew2"),
			scrapeConfig: &config.ScrapeConfig{},
		}
		proxyURL, _ = url.Parse("http://localhost:2128")
	)
	defer sp.stop()
	sp.sync([]*Target{t1})

	steps := []struct {
		keep      bool
		newConfig *config.ScrapeConfig
	}{
		{
			keep: true,
			newConfig: &config.ScrapeConfig{
				JobName:        "Prometheus",
				ScrapeInterval: model.Duration(5 * time.Second),
				ScrapeTimeout:  model.Duration(5 * time.Second),
				MetricsPath:    "/metrics",
			},
		},
		{
			keep: false,
			newConfig: &config.ScrapeConfig{
				JobName:        "Prometheus",
				ScrapeInterval: model.Duration(5 * time.Second),
				ScrapeTimeout:  model.Duration(15 * time.Second),
				MetricsPath:    "/metrics2",
			},
		},
		{
			keep: true,
			newConfig: &config.ScrapeConfig{
				JobName:        "Prometheus",
				SampleLimit:    400,
				ScrapeInterval: model.Duration(5 * time.Second),
				ScrapeTimeout:  model.Duration(15 * time.Second),
				MetricsPath:    "/metrics2",
			},
		},
		{
			keep: false,
			newConfig: &config.ScrapeConfig{
				JobName:         "Prometheus",
				HonorTimestamps: true,
				SampleLimit:     400,
				ScrapeInterval:  model.Duration(5 * time.Second),
				ScrapeTimeout:   model.Duration(15 * time.Second),
				MetricsPath:     "/metrics2",
			},
		},
		{
			keep: true,
			newConfig: &config.ScrapeConfig{
				JobName:         "Prometheus",
				HonorTimestamps: true,
				SampleLimit:     400,
				HTTPClientConfig: config_util.HTTPClientConfig{
					ProxyConfig: config_util.ProxyConfig{ProxyURL: config_util.URL{URL: proxyURL}},
				},
				ScrapeInterval: model.Duration(5 * time.Second),
				ScrapeTimeout:  model.Duration(15 * time.Second),
				MetricsPath:    "/metrics2",
			},
		},
		{
			keep: false,
			newConfig: &config.ScrapeConfig{
				JobName:         "Prometheus",
				HonorTimestamps: true,
				HonorLabels:     true,
				SampleLimit:     400,
				ScrapeInterval:  model.Duration(5 * time.Second),
				ScrapeTimeout:   model.Duration(15 * time.Second),
				MetricsPath:     "/metrics2",
			},
		},
		{
			keep: false,
			newConfig: &config.ScrapeConfig{
				JobName:        "Prometheus",
				ScrapeInterval: model.Duration(5 * time.Second),
				ScrapeTimeout:  model.Duration(15 * time.Second),
				MetricsPath:    "/metrics",
				LabelLimit:     1,
			},
		},
		{
			keep: false,
			newConfig: &config.ScrapeConfig{
				JobName:        "Prometheus",
				ScrapeInterval: model.Duration(5 * time.Second),
				ScrapeTimeout:  model.Duration(15 * time.Second),
				MetricsPath:    "/metrics",
				LabelLimit:     15,
			},
		},
		{
			keep: false,
			newConfig: &config.ScrapeConfig{
				JobName:              "Prometheus",
				ScrapeInterval:       model.Duration(5 * time.Second),
				ScrapeTimeout:        model.Duration(15 * time.Second),
				MetricsPath:          "/metrics",
				LabelLimit:           15,
				LabelNameLengthLimit: 5,
			},
		},
		{
			keep: false,
			newConfig: &config.ScrapeConfig{
				JobName:               "Prometheus",
				ScrapeInterval:        model.Duration(5 * time.Second),
				ScrapeTimeout:         model.Duration(15 * time.Second),
				MetricsPath:           "/metrics",
				LabelLimit:            15,
				LabelNameLengthLimit:  5,
				LabelValueLengthLimit: 7,
			},
		},
	}

	cacheAddr := func(sp *scrapePool) map[uint64]string {
		r := make(map[uint64]string)
		for fp, l := range sp.loops {
			r[fp] = fmt.Sprintf("%p", l.getCache())
		}
		return r
	}

	for i, s := range steps {
		initCacheAddr := cacheAddr(sp)
		sp.reload(s.newConfig)
		for fp, newCacheAddr := range cacheAddr(sp) {
			if s.keep {
				require.Equal(t, initCacheAddr[fp], newCacheAddr, "step %d: old cache and new cache are not the same", i)
			} else {
				require.NotEqual(t, initCacheAddr[fp], newCacheAddr, "step %d: old cache and new cache are the same", i)
			}
		}
		initCacheAddr = cacheAddr(sp)
		sp.reload(s.newConfig)
		for fp, newCacheAddr := range cacheAddr(sp) {
			require.Equal(t, initCacheAddr[fp], newCacheAddr, "step %d: reloading the exact config invalidates the cache", i)
		}
	}
}

func TestScrapeAddFast(t *testing.T) {
	s := teststorage.New(t)
	defer s.Close()

	ctx, cancel := context.WithCancel(context.Background())
	sl := newBasicScrapeLoop(t, ctx, &testScraper{}, s.Appender, 0)
	defer cancel()

	slApp := sl.appender(ctx)
	_, _, _, err := sl.append(slApp, []byte("up 1\n"), "text/plain", time.Time{})
	require.NoError(t, err)
	require.NoError(t, slApp.Commit())

	// Poison the cache. There is just one entry, and one series in the
	// storage. Changing the ref will create a 'not found' error.
	for _, v := range sl.getCache().series {
		v.ref++
	}

	slApp = sl.appender(ctx)
	_, _, _, err = sl.append(slApp, []byte("up 1\n"), "text/plain", time.Time{}.Add(time.Second))
	require.NoError(t, err)
	require.NoError(t, slApp.Commit())
}

func TestReuseCacheRace(t *testing.T) {
	var (
		app = &nopAppendable{}
		cfg = &config.ScrapeConfig{
			JobName:        "Prometheus",
			ScrapeTimeout:  model.Duration(5 * time.Second),
			ScrapeInterval: model.Duration(5 * time.Second),
			MetricsPath:    "/metrics",
		}
		buffers = pool.New(1e3, 100e6, 3, func(sz int) interface{} { return make([]byte, 0, sz) })
		sp, _   = newScrapePool(cfg, app, 0, nil, buffers, &Options{}, newTestScrapeMetrics(t))
		t1      = &Target{
			labels:       labels.FromStrings("labelNew", "nameNew"),
			scrapeConfig: &config.ScrapeConfig{},
		}
	)
	defer sp.stop()
	sp.sync([]*Target{t1})

	start := time.Now()
	for i := uint(1); i > 0; i++ {
		if time.Since(start) > 5*time.Second {
			break
		}
		sp.reload(&config.ScrapeConfig{
			JobName:        "Prometheus",
			ScrapeTimeout:  model.Duration(1 * time.Millisecond),
			ScrapeInterval: model.Duration(1 * time.Millisecond),
			MetricsPath:    "/metrics",
			SampleLimit:    i,
		})
	}
}

func TestCheckAddError(t *testing.T) {
	var appErrs appendErrors
	sl := scrapeLoop{l: promslog.NewNopLogger(), metrics: newTestScrapeMetrics(t)}
	sl.checkAddError(nil, storage.ErrOutOfOrderSample, nil, nil, &appErrs)
	require.Equal(t, 1, appErrs.numOutOfOrder)
}

func TestScrapeReportSingleAppender(t *testing.T) {
	s := teststorage.New(t)
	defer s.Close()

	var (
		signal  = make(chan struct{}, 1)
		scraper = &testScraper{}
	)

	ctx, cancel := context.WithCancel(context.Background())
	// Since we're writing samples directly below we need to provide a protocol fallback.
	sl := newBasicScrapeLoopWithFallback(t, ctx, scraper, s.Appender, 10*time.Millisecond, "text/plain")

	numScrapes := 0

	scraper.scrapeFunc = func(ctx context.Context, w io.Writer) error {
		numScrapes++
		if numScrapes%4 == 0 {
			return errors.New("scrape failed")
		}
		w.Write([]byte("metric_a 44\nmetric_b 44\nmetric_c 44\nmetric_d 44\n"))
		return nil
	}

	go func() {
		sl.run(nil)
		signal <- struct{}{}
	}()

	start := time.Now()
	for time.Since(start) < 3*time.Second {
		q, err := s.Querier(time.Time{}.UnixNano(), time.Now().UnixNano())
		require.NoError(t, err)
		series := q.Select(ctx, false, nil, labels.MustNewMatcher(labels.MatchRegexp, "__name__", ".+"))

		c := 0
		for series.Next() {
			i := series.At().Iterator(nil)
			for i.Next() != chunkenc.ValNone {
				c++
			}
		}

		require.Equal(t, 0, c%9, "Appended samples not as expected: %d", c)
		q.Close()
	}
	cancel()

	select {
	case <-signal:
	case <-time.After(5 * time.Second):
		require.FailNow(t, "Scrape wasn't stopped.")
	}
}

func TestScrapeReportLimit(t *testing.T) {
	s := teststorage.New(t)
	defer s.Close()

	cfg := &config.ScrapeConfig{
		JobName:        "test",
		SampleLimit:    5,
		Scheme:         "http",
		ScrapeInterval: model.Duration(100 * time.Millisecond),
		ScrapeTimeout:  model.Duration(100 * time.Millisecond),
	}

	ts, scrapedTwice := newScrapableServer("metric_a 44\nmetric_b 44\nmetric_c 44\nmetric_d 44\n")
	defer ts.Close()

	sp, err := newScrapePool(cfg, s, 0, nil, nil, &Options{}, newTestScrapeMetrics(t))
	require.NoError(t, err)
	defer sp.stop()

	testURL, err := url.Parse(ts.URL)
	require.NoError(t, err)
	sp.Sync([]*targetgroup.Group{
		{
			Targets: []model.LabelSet{{model.AddressLabel: model.LabelValue(testURL.Host)}},
		},
	})

	select {
	case <-time.After(5 * time.Second):
		t.Fatalf("target was not scraped twice")
	case <-scrapedTwice:
		// If the target has been scraped twice, report samples from the first
		// scrape have been inserted in the database.
	}

	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()
	q, err := s.Querier(time.Time{}.UnixNano(), time.Now().UnixNano())
	require.NoError(t, err)
	defer q.Close()
	series := q.Select(ctx, false, nil, labels.MustNewMatcher(labels.MatchRegexp, "__name__", "up"))

	var found bool
	for series.Next() {
		i := series.At().Iterator(nil)
		for i.Next() == chunkenc.ValFloat {
			_, v := i.At()
			require.Equal(t, 1.0, v)
			found = true
		}
	}

	require.True(t, found)
}

func TestScrapeUTF8(t *testing.T) {
	s := teststorage.New(t)
	defer s.Close()
	model.NameValidationScheme = model.UTF8Validation
	t.Cleanup(func() { model.NameValidationScheme = model.LegacyValidation })

	cfg := &config.ScrapeConfig{
		JobName:                    "test",
		Scheme:                     "http",
		ScrapeInterval:             model.Duration(100 * time.Millisecond),
		ScrapeTimeout:              model.Duration(100 * time.Millisecond),
		MetricNameValidationScheme: config.UTF8ValidationConfig,
	}
	ts, scrapedTwice := newScrapableServer("{\"with.dots\"} 42\n")
	defer ts.Close()

	sp, err := newScrapePool(cfg, s, 0, nil, nil, &Options{}, newTestScrapeMetrics(t))
	require.NoError(t, err)
	defer sp.stop()

	testURL, err := url.Parse(ts.URL)
	require.NoError(t, err)
	sp.Sync([]*targetgroup.Group{
		{
			Targets: []model.LabelSet{{model.AddressLabel: model.LabelValue(testURL.Host)}},
		},
	})

	select {
	case <-time.After(5 * time.Second):
		t.Fatalf("target was not scraped twice")
	case <-scrapedTwice:
		// If the target has been scraped twice, report samples from the first
		// scrape have been inserted in the database.
	}

	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()
	q, err := s.Querier(time.Time{}.UnixNano(), time.Now().UnixNano())
	require.NoError(t, err)
	defer q.Close()
	series := q.Select(ctx, false, nil, labels.MustNewMatcher(labels.MatchRegexp, "__name__", "with.dots"))

	require.True(t, series.Next(), "series not found in tsdb")
}

func TestScrapeLoopLabelLimit(t *testing.T) {
	tests := []struct {
		title           string
		scrapeLabels    string
		discoveryLabels []string
		labelLimits     labelLimits
		expectErr       bool
	}{
		{
			title:           "Valid number of labels",
			scrapeLabels:    `metric{l1="1", l2="2"} 0`,
			discoveryLabels: nil,
			labelLimits:     labelLimits{labelLimit: 5},
			expectErr:       false,
		}, {
			title:           "Too many labels",
			scrapeLabels:    `metric{l1="1", l2="2", l3="3", l4="4", l5="5", l6="6"} 0`,
			discoveryLabels: nil,
			labelLimits:     labelLimits{labelLimit: 5},
			expectErr:       true,
		}, {
			title:           "Too many labels including discovery labels",
			scrapeLabels:    `metric{l1="1", l2="2", l3="3", l4="4"} 0`,
			discoveryLabels: []string{"l5", "5", "l6", "6"},
			labelLimits:     labelLimits{labelLimit: 5},
			expectErr:       true,
		}, {
			title:           "Valid labels name length",
			scrapeLabels:    `metric{l1="1", l2="2"} 0`,
			discoveryLabels: nil,
			labelLimits:     labelLimits{labelNameLengthLimit: 10},
			expectErr:       false,
		}, {
			title:           "Label name too long",
			scrapeLabels:    `metric{label_name_too_long="0"} 0`,
			discoveryLabels: nil,
			labelLimits:     labelLimits{labelNameLengthLimit: 10},
			expectErr:       true,
		}, {
			title:           "Discovery label name too long",
			scrapeLabels:    `metric{l1="1", l2="2"} 0`,
			discoveryLabels: []string{"label_name_too_long", "0"},
			labelLimits:     labelLimits{labelNameLengthLimit: 10},
			expectErr:       true,
		}, {
			title:           "Valid labels value length",
			scrapeLabels:    `metric{l1="1", l2="2"} 0`,
			discoveryLabels: nil,
			labelLimits:     labelLimits{labelValueLengthLimit: 10},
			expectErr:       false,
		}, {
			title:           "Label value too long",
			scrapeLabels:    `metric{l1="label_value_too_long"} 0`,
			discoveryLabels: nil,
			labelLimits:     labelLimits{labelValueLengthLimit: 10},
			expectErr:       true,
		}, {
			title:           "Discovery label value too long",
			scrapeLabels:    `metric{l1="1", l2="2"} 0`,
			discoveryLabels: []string{"l1", "label_value_too_long"},
			labelLimits:     labelLimits{labelValueLengthLimit: 10},
			expectErr:       true,
		},
	}

	for _, test := range tests {
		app := &collectResultAppender{}

		discoveryLabels := &Target{
			labels: labels.FromStrings(test.discoveryLabels...),
		}

		sl := newBasicScrapeLoop(t, context.Background(), nil, func(ctx context.Context) storage.Appender { return app }, 0)
		sl.sampleMutator = func(l labels.Labels) labels.Labels {
			return mutateSampleLabels(l, discoveryLabels, false, nil)
		}
		sl.reportSampleMutator = func(l labels.Labels) labels.Labels {
			return mutateReportSampleLabels(l, discoveryLabels)
		}
		sl.labelLimits = &test.labelLimits

		slApp := sl.appender(context.Background())
		_, _, _, err := sl.append(slApp, []byte(test.scrapeLabels), "text/plain", time.Now())

		t.Logf("Test:%s", test.title)
		if test.expectErr {
			require.Error(t, err)
		} else {
			require.NoError(t, err)
			require.NoError(t, slApp.Commit())
		}
	}
}

func TestTargetScrapeIntervalAndTimeoutRelabel(t *testing.T) {
	interval, _ := model.ParseDuration("2s")
	timeout, _ := model.ParseDuration("500ms")
	config := &config.ScrapeConfig{
		ScrapeInterval: interval,
		ScrapeTimeout:  timeout,
		RelabelConfigs: []*relabel.Config{
			{
				SourceLabels: model.LabelNames{model.ScrapeIntervalLabel},
				Regex:        relabel.MustNewRegexp("2s"),
				Replacement:  "3s",
				TargetLabel:  model.ScrapeIntervalLabel,
				Action:       relabel.Replace,
			},
			{
				SourceLabels: model.LabelNames{model.ScrapeTimeoutLabel},
				Regex:        relabel.MustNewRegexp("500ms"),
				Replacement:  "750ms",
				TargetLabel:  model.ScrapeTimeoutLabel,
				Action:       relabel.Replace,
			},
		},
	}
	sp, _ := newScrapePool(config, &nopAppendable{}, 0, nil, nil, &Options{}, newTestScrapeMetrics(t))
	tgts := []*targetgroup.Group{
		{
			Targets: []model.LabelSet{{model.AddressLabel: "127.0.0.1:9090"}},
		},
	}

	sp.Sync(tgts)
	defer sp.stop()

	require.Equal(t, "3s", sp.ActiveTargets()[0].labels.Get(model.ScrapeIntervalLabel))
	require.Equal(t, "750ms", sp.ActiveTargets()[0].labels.Get(model.ScrapeTimeoutLabel))
}

// Testing whether we can remove trailing .0 from histogram 'le' and summary 'quantile' labels.
func TestLeQuantileReLabel(t *testing.T) {
	simpleStorage := teststorage.New(t)
	defer simpleStorage.Close()

	config := &config.ScrapeConfig{
		JobName: "test",
		MetricRelabelConfigs: []*relabel.Config{
			{
				SourceLabels: model.LabelNames{"le", "__name__"},
				Regex:        relabel.MustNewRegexp("(\\d+)\\.0+;.*_bucket"),
				Replacement:  relabel.DefaultRelabelConfig.Replacement,
				Separator:    relabel.DefaultRelabelConfig.Separator,
				TargetLabel:  "le",
				Action:       relabel.Replace,
			},
			{
				SourceLabels: model.LabelNames{"quantile"},
				Regex:        relabel.MustNewRegexp("(\\d+)\\.0+"),
				Replacement:  relabel.DefaultRelabelConfig.Replacement,
				Separator:    relabel.DefaultRelabelConfig.Separator,
				TargetLabel:  "quantile",
				Action:       relabel.Replace,
			},
		},
		SampleLimit:    100,
		Scheme:         "http",
		ScrapeInterval: model.Duration(100 * time.Millisecond),
		ScrapeTimeout:  model.Duration(100 * time.Millisecond),
	}

	metricsText := `
# HELP test_histogram This is a histogram with default buckets
# TYPE test_histogram histogram
test_histogram_bucket{address="0.0.0.0",port="5001",le="0.005"} 0
test_histogram_bucket{address="0.0.0.0",port="5001",le="0.01"} 0
test_histogram_bucket{address="0.0.0.0",port="5001",le="0.025"} 0
test_histogram_bucket{address="0.0.0.0",port="5001",le="0.05"} 0
test_histogram_bucket{address="0.0.0.0",port="5001",le="0.1"} 0
test_histogram_bucket{address="0.0.0.0",port="5001",le="0.25"} 0
test_histogram_bucket{address="0.0.0.0",port="5001",le="0.5"} 0
test_histogram_bucket{address="0.0.0.0",port="5001",le="1.0"} 0
test_histogram_bucket{address="0.0.0.0",port="5001",le="2.5"} 0
test_histogram_bucket{address="0.0.0.0",port="5001",le="5.0"} 0
test_histogram_bucket{address="0.0.0.0",port="5001",le="10.0"} 0
test_histogram_bucket{address="0.0.0.0",port="5001",le="+Inf"} 0
test_histogram_sum{address="0.0.0.0",port="5001"} 0
test_histogram_count{address="0.0.0.0",port="5001"} 0
# HELP test_summary Number of inflight requests sampled at a regular interval. Quantile buckets keep track of inflight requests over the last 60s.
# TYPE test_summary summary
test_summary{quantile="0.5"} 0
test_summary{quantile="0.9"} 0
test_summary{quantile="0.95"} 0
test_summary{quantile="0.99"} 0
test_summary{quantile="1.0"} 1
test_summary_sum 1
test_summary_count 199
`

	// The expected "le" values do not have the trailing ".0".
	expectedLeValues := []string{"0.005", "0.01", "0.025", "0.05", "0.1", "0.25", "0.5", "1", "2.5", "5", "10", "+Inf"}

	// The expected "quantile" values do not have the trailing ".0".
	expectedQuantileValues := []string{"0.5", "0.9", "0.95", "0.99", "1"}

	ts, scrapedTwice := newScrapableServer(metricsText)
	defer ts.Close()

	sp, err := newScrapePool(config, simpleStorage, 0, nil, nil, &Options{}, newTestScrapeMetrics(t))
	require.NoError(t, err)
	defer sp.stop()

	testURL, err := url.Parse(ts.URL)
	require.NoError(t, err)
	sp.Sync([]*targetgroup.Group{
		{
			Targets: []model.LabelSet{{model.AddressLabel: model.LabelValue(testURL.Host)}},
		},
	})
	require.Len(t, sp.ActiveTargets(), 1)

	select {
	case <-time.After(5 * time.Second):
		t.Fatalf("target was not scraped")
	case <-scrapedTwice:
	}

	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()
	q, err := simpleStorage.Querier(time.Time{}.UnixNano(), time.Now().UnixNano())
	require.NoError(t, err)
	defer q.Close()

	checkValues := func(labelName string, expectedValues []string, series storage.SeriesSet) {
		foundLeValues := map[string]bool{}

		for series.Next() {
			s := series.At()
			v := s.Labels().Get(labelName)
			require.NotContains(t, foundLeValues, v, "duplicate label value found")
			foundLeValues[v] = true
		}

		require.Equal(t, len(expectedValues), len(foundLeValues), "number of label values not as expected")
		for _, v := range expectedValues {
			require.Contains(t, foundLeValues, v, "label value not found")
		}
	}

	series := q.Select(ctx, false, nil, labels.MustNewMatcher(labels.MatchRegexp, "__name__", "test_histogram_bucket"))
	checkValues("le", expectedLeValues, series)

	series = q.Select(ctx, false, nil, labels.MustNewMatcher(labels.MatchRegexp, "__name__", "test_summary"))
	checkValues("quantile", expectedQuantileValues, series)
}

// Testing whether we can automatically convert scraped classic histograms into native histograms with custom buckets.
func TestConvertClassicHistogramsToNHCB(t *testing.T) {
	genTestCounterText := func(name string, value int, withMetadata bool) string {
		if withMetadata {
			return fmt.Sprintf(`
# HELP %s some help text
# TYPE %s counter
%s{address="0.0.0.0",port="5001"} %d
`, name, name, name, value)
		}
		return fmt.Sprintf(`
%s %d
`, name, value)
	}
	genTestHistText := func(name string, withMetadata bool) string {
		data := map[string]interface{}{
			"name": name,
		}
		b := &bytes.Buffer{}
		if withMetadata {
			template.Must(template.New("").Parse(`
# HELP {{.name}} This is a histogram with default buckets
# TYPE {{.name}} histogram
`)).Execute(b, data)
		}
		template.Must(template.New("").Parse(`
{{.name}}_bucket{address="0.0.0.0",port="5001",le="0.005"} 0
{{.name}}_bucket{address="0.0.0.0",port="5001",le="0.01"} 0
{{.name}}_bucket{address="0.0.0.0",port="5001",le="0.025"} 0
{{.name}}_bucket{address="0.0.0.0",port="5001",le="0.05"} 0
{{.name}}_bucket{address="0.0.0.0",port="5001",le="0.1"} 0
{{.name}}_bucket{address="0.0.0.0",port="5001",le="0.25"} 0
{{.name}}_bucket{address="0.0.0.0",port="5001",le="0.5"} 0
{{.name}}_bucket{address="0.0.0.0",port="5001",le="1"} 0
{{.name}}_bucket{address="0.0.0.0",port="5001",le="2.5"} 0
{{.name}}_bucket{address="0.0.0.0",port="5001",le="5"} 0
{{.name}}_bucket{address="0.0.0.0",port="5001",le="10"} 1
{{.name}}_bucket{address="0.0.0.0",port="5001",le="+Inf"} 1
{{.name}}_sum{address="0.0.0.0",port="5001"} 10
{{.name}}_count{address="0.0.0.0",port="5001"} 1
`)).Execute(b, data)
		return b.String()
	}
	genTestCounterProto := func(name string, value int) string {
		return fmt.Sprintf(`
name: "%s"
help: "some help text"
type: COUNTER
metric: <
	label: <
		name: "address"
		value: "0.0.0.0"
	>
	label: <
		name: "port"
		value: "5001"
	>
	counter: <
		value: %d
	>
>
`, name, value)
	}
	genTestHistProto := func(name string, hasClassic, hasExponential bool) string {
		var classic string
		if hasClassic {
			classic = `
bucket: <
	cumulative_count: 0
	upper_bound: 0.005
>
bucket: <
	cumulative_count: 0
	upper_bound: 0.01
>
bucket: <
	cumulative_count: 0
	upper_bound: 0.025
>
bucket: <
	cumulative_count: 0
	upper_bound: 0.05
>
bucket: <
	cumulative_count: 0
	upper_bound: 0.1
>
bucket: <
	cumulative_count: 0
	upper_bound: 0.25
>
bucket: <
	cumulative_count: 0
	upper_bound: 0.5
>
bucket: <
	cumulative_count: 0
	upper_bound: 1
>
bucket: <
	cumulative_count: 0
	upper_bound: 2.5
>
bucket: <
	cumulative_count: 0
	upper_bound: 5
>
bucket: <
	cumulative_count: 1
	upper_bound: 10
>`
		}
		var expo string
		if hasExponential {
			expo = `
schema: 3
zero_threshold: 2.938735877055719e-39
zero_count: 0
positive_span: <
	offset: 2
	length: 1
>
positive_delta: 1`
		}
		return fmt.Sprintf(`
name: "%s"
help: "This is a histogram with default buckets"
type: HISTOGRAM
metric: <
	label: <
		name: "address"
		value: "0.0.0.0"
	>
	label: <
		name: "port"
		value: "5001"
	>
	histogram: <
		sample_count: 1
		sample_sum: 10
		%s
		%s
	>
	timestamp_ms: 1234568
>
`, name, classic, expo)
	}

	metricsTexts := map[string]struct {
		text           []string
		contentType    string
		hasClassic     bool
		hasExponential bool
	}{
		"text": {
			text: []string{
				genTestCounterText("test_metric_1", 1, true),
				genTestCounterText("test_metric_1_count", 1, true),
				genTestCounterText("test_metric_1_sum", 1, true),
				genTestCounterText("test_metric_1_bucket", 1, true),
				genTestHistText("test_histogram_1", true),
				genTestCounterText("test_metric_2", 1, true),
				genTestCounterText("test_metric_2_count", 1, true),
				genTestCounterText("test_metric_2_sum", 1, true),
				genTestCounterText("test_metric_2_bucket", 1, true),
				genTestHistText("test_histogram_2", true),
				genTestCounterText("test_metric_3", 1, true),
				genTestCounterText("test_metric_3_count", 1, true),
				genTestCounterText("test_metric_3_sum", 1, true),
				genTestCounterText("test_metric_3_bucket", 1, true),
				genTestHistText("test_histogram_3", true),
			},
			hasClassic: true,
		},
		"text, in different order": {
			text: []string{
				genTestCounterText("test_metric_1", 1, true),
				genTestCounterText("test_metric_1_count", 1, true),
				genTestCounterText("test_metric_1_sum", 1, true),
				genTestCounterText("test_metric_1_bucket", 1, true),
				genTestHistText("test_histogram_1", true),
				genTestCounterText("test_metric_2", 1, true),
				genTestCounterText("test_metric_2_count", 1, true),
				genTestCounterText("test_metric_2_sum", 1, true),
				genTestCounterText("test_metric_2_bucket", 1, true),
				genTestHistText("test_histogram_2", true),
				genTestHistText("test_histogram_3", true),
				genTestCounterText("test_metric_3", 1, true),
				genTestCounterText("test_metric_3_count", 1, true),
				genTestCounterText("test_metric_3_sum", 1, true),
				genTestCounterText("test_metric_3_bucket", 1, true),
			},
			hasClassic: true,
		},
		"protobuf": {
			text: []string{
				genTestCounterProto("test_metric_1", 1),
				genTestCounterProto("test_metric_1_count", 1),
				genTestCounterProto("test_metric_1_sum", 1),
				genTestCounterProto("test_metric_1_bucket", 1),
				genTestHistProto("test_histogram_1", true, false),
				genTestCounterProto("test_metric_2", 1),
				genTestCounterProto("test_metric_2_count", 1),
				genTestCounterProto("test_metric_2_sum", 1),
				genTestCounterProto("test_metric_2_bucket", 1),
				genTestHistProto("test_histogram_2", true, false),
				genTestCounterProto("test_metric_3", 1),
				genTestCounterProto("test_metric_3_count", 1),
				genTestCounterProto("test_metric_3_sum", 1),
				genTestCounterProto("test_metric_3_bucket", 1),
				genTestHistProto("test_histogram_3", true, false),
			},
			contentType: "application/vnd.google.protobuf",
			hasClassic:  true,
		},
		"protobuf, in different order": {
			text: []string{
				genTestHistProto("test_histogram_1", true, false),
				genTestCounterProto("test_metric_1", 1),
				genTestCounterProto("test_metric_1_count", 1),
				genTestCounterProto("test_metric_1_sum", 1),
				genTestCounterProto("test_metric_1_bucket", 1),
				genTestHistProto("test_histogram_2", true, false),
				genTestCounterProto("test_metric_2", 1),
				genTestCounterProto("test_metric_2_count", 1),
				genTestCounterProto("test_metric_2_sum", 1),
				genTestCounterProto("test_metric_2_bucket", 1),
				genTestHistProto("test_histogram_3", true, false),
				genTestCounterProto("test_metric_3", 1),
				genTestCounterProto("test_metric_3_count", 1),
				genTestCounterProto("test_metric_3_sum", 1),
				genTestCounterProto("test_metric_3_bucket", 1),
			},
			contentType: "application/vnd.google.protobuf",
			hasClassic:  true,
		},
		"protobuf, with additional native exponential histogram": {
			text: []string{
				genTestCounterProto("test_metric_1", 1),
				genTestCounterProto("test_metric_1_count", 1),
				genTestCounterProto("test_metric_1_sum", 1),
				genTestCounterProto("test_metric_1_bucket", 1),
				genTestHistProto("test_histogram_1", true, true),
				genTestCounterProto("test_metric_2", 1),
				genTestCounterProto("test_metric_2_count", 1),
				genTestCounterProto("test_metric_2_sum", 1),
				genTestCounterProto("test_metric_2_bucket", 1),
				genTestHistProto("test_histogram_2", true, true),
				genTestCounterProto("test_metric_3", 1),
				genTestCounterProto("test_metric_3_count", 1),
				genTestCounterProto("test_metric_3_sum", 1),
				genTestCounterProto("test_metric_3_bucket", 1),
				genTestHistProto("test_histogram_3", true, true),
			},
			contentType:    "application/vnd.google.protobuf",
			hasClassic:     true,
			hasExponential: true,
		},
		"protobuf, with only native exponential histogram": {
			text: []string{
				genTestCounterProto("test_metric_1", 1),
				genTestCounterProto("test_metric_1_count", 1),
				genTestCounterProto("test_metric_1_sum", 1),
				genTestCounterProto("test_metric_1_bucket", 1),
				genTestHistProto("test_histogram_1", false, true),
				genTestCounterProto("test_metric_2", 1),
				genTestCounterProto("test_metric_2_count", 1),
				genTestCounterProto("test_metric_2_sum", 1),
				genTestCounterProto("test_metric_2_bucket", 1),
				genTestHistProto("test_histogram_2", false, true),
				genTestCounterProto("test_metric_3", 1),
				genTestCounterProto("test_metric_3_count", 1),
				genTestCounterProto("test_metric_3_sum", 1),
				genTestCounterProto("test_metric_3_bucket", 1),
				genTestHistProto("test_histogram_3", false, true),
			},
			contentType:    "application/vnd.google.protobuf",
			hasExponential: true,
		},
	}

	checkBucketValues := func(expectedCount int, series storage.SeriesSet) {
		labelName := "le"
		var expectedValues []string
		if expectedCount > 0 {
			expectedValues = []string{"0.005", "0.01", "0.025", "0.05", "0.1", "0.25", "0.5", "1.0", "2.5", "5.0", "10.0", "+Inf"}
		}
		foundLeValues := map[string]bool{}

		for series.Next() {
			s := series.At()
			v := s.Labels().Get(labelName)
			require.NotContains(t, foundLeValues, v, "duplicate label value found")
			foundLeValues[v] = true
		}

		require.Equal(t, len(expectedValues), len(foundLeValues), "unexpected number of label values, expected %v but found %v", expectedValues, foundLeValues)
		for _, v := range expectedValues {
			require.Contains(t, foundLeValues, v, "label value not found")
		}
	}

	// Checks that the expected series is present and runs a basic sanity check of the float values.
	checkFloatSeries := func(series storage.SeriesSet, expectedCount int, expectedFloat float64) {
		count := 0
		for series.Next() {
			i := series.At().Iterator(nil)
		loop:
			for {
				switch i.Next() {
				case chunkenc.ValNone:
					break loop
				case chunkenc.ValFloat:
					_, f := i.At()
					require.Equal(t, expectedFloat, f)
				case chunkenc.ValHistogram:
					panic("unexpected value type: histogram")
				case chunkenc.ValFloatHistogram:
					panic("unexpected value type: float histogram")
				default:
					panic("unexpected value type")
				}
			}
			count++
		}
		require.Equal(t, expectedCount, count, "number of float series not as expected")
	}

	// Checks that the expected series is present and runs a basic sanity check of the histogram values.
	checkHistSeries := func(series storage.SeriesSet, expectedCount int, expectedSchema int32) {
		count := 0
		for series.Next() {
			i := series.At().Iterator(nil)
		loop:
			for {
				switch i.Next() {
				case chunkenc.ValNone:
					break loop
				case chunkenc.ValFloat:
					panic("unexpected value type: float")
				case chunkenc.ValHistogram:
					_, h := i.AtHistogram(nil)
					require.Equal(t, expectedSchema, h.Schema)
					require.Equal(t, uint64(1), h.Count)
					require.Equal(t, 10.0, h.Sum)
				case chunkenc.ValFloatHistogram:
					_, h := i.AtFloatHistogram(nil)
					require.Equal(t, expectedSchema, h.Schema)
					require.Equal(t, uint64(1), h.Count)
					require.Equal(t, 10.0, h.Sum)
				default:
					panic("unexpected value type")
				}
			}
			count++
		}
		require.Equal(t, expectedCount, count, "number of histogram series not as expected")
	}

	for metricsTextName, metricsText := range metricsTexts {
		for name, tc := range map[string]struct {
			alwaysScrapeClassicHistograms bool
			convertClassicHistToNHCB      bool
		}{
			"convert with scrape": {
				alwaysScrapeClassicHistograms: true,
				convertClassicHistToNHCB:      true,
			},
			"convert without scrape": {
				alwaysScrapeClassicHistograms: false,
				convertClassicHistToNHCB:      true,
			},
			"scrape without convert": {
				alwaysScrapeClassicHistograms: true,
				convertClassicHistToNHCB:      false,
			},
			"neither scrape nor convert": {
				alwaysScrapeClassicHistograms: false,
				convertClassicHistToNHCB:      false,
			},
		} {
			var expectedClassicHistCount, expectedNativeHistCount int
			var expectCustomBuckets bool
			if metricsText.hasExponential {
				expectedNativeHistCount = 1
				expectCustomBuckets = false
				expectedClassicHistCount = 0
				if metricsText.hasClassic && tc.alwaysScrapeClassicHistograms {
					expectedClassicHistCount = 1
				}
			} else if metricsText.hasClassic {
				switch {
				case tc.alwaysScrapeClassicHistograms && tc.convertClassicHistToNHCB:
					expectedClassicHistCount = 1
					expectedNativeHistCount = 1
					expectCustomBuckets = true
				case !tc.alwaysScrapeClassicHistograms && tc.convertClassicHistToNHCB:
					expectedClassicHistCount = 0
					expectedNativeHistCount = 1
					expectCustomBuckets = true
				case !tc.convertClassicHistToNHCB:
					expectedClassicHistCount = 1
					expectedNativeHistCount = 0
				}
			}

			t.Run(fmt.Sprintf("%s with %s", name, metricsTextName), func(t *testing.T) {
				simpleStorage := teststorage.New(t)
				defer simpleStorage.Close()

				config := &config.ScrapeConfig{
					JobName:                        "test",
					SampleLimit:                    100,
					Scheme:                         "http",
					ScrapeInterval:                 model.Duration(50 * time.Millisecond),
					ScrapeTimeout:                  model.Duration(25 * time.Millisecond),
					AlwaysScrapeClassicHistograms:  tc.alwaysScrapeClassicHistograms,
					ConvertClassicHistogramsToNHCB: tc.convertClassicHistToNHCB,
				}

				scrapeCount := 0
				scraped := make(chan bool)

				ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
					if metricsText.contentType != "" {
						w.Header().Set("Content-Type", `application/vnd.google.protobuf; proto=io.prometheus.client.MetricFamily; encoding=delimited`)
						for _, text := range metricsText.text {
							buf := &bytes.Buffer{}
							// In case of protobuf, we have to create the binary representation.
							pb := &dto.MetricFamily{}
							// From text to proto message.
							require.NoError(t, proto.UnmarshalText(text, pb))
							// From proto message to binary protobuf.
							protoBuf, err := proto.Marshal(pb)
							require.NoError(t, err)

							// Write first length, then binary protobuf.
							varintBuf := binary.AppendUvarint(nil, uint64(len(protoBuf)))
							buf.Write(varintBuf)
							buf.Write(protoBuf)
							w.Write(buf.Bytes())
						}
					} else {
						for _, text := range metricsText.text {
							fmt.Fprint(w, text)
						}
					}
					scrapeCount++
					if scrapeCount > 2 {
						close(scraped)
					}
				}))
				defer ts.Close()

				sp, err := newScrapePool(config, simpleStorage, 0, nil, nil, &Options{DiscoveryReloadInterval: model.Duration(10 * time.Millisecond), EnableNativeHistogramsIngestion: true}, newTestScrapeMetrics(t))
				require.NoError(t, err)
				defer sp.stop()

				testURL, err := url.Parse(ts.URL)
				require.NoError(t, err)
				sp.Sync([]*targetgroup.Group{
					{
						Targets: []model.LabelSet{{model.AddressLabel: model.LabelValue(testURL.Host)}},
					},
				})
				require.Len(t, sp.ActiveTargets(), 1)

				select {
				case <-time.After(5 * time.Second):
					t.Fatalf("target was not scraped")
				case <-scraped:
				}

				ctx, cancel := context.WithCancel(context.Background())
				defer cancel()
				q, err := simpleStorage.Querier(time.Time{}.UnixNano(), time.Now().UnixNano())
				require.NoError(t, err)
				defer q.Close()

				var series storage.SeriesSet

				for i := 1; i <= 3; i++ {
					series = q.Select(ctx, false, nil, labels.MustNewMatcher(labels.MatchRegexp, "__name__", fmt.Sprintf("test_metric_%d", i)))
					checkFloatSeries(series, 1, 1.)

					series = q.Select(ctx, false, nil, labels.MustNewMatcher(labels.MatchRegexp, "__name__", fmt.Sprintf("test_metric_%d_count", i)))
					checkFloatSeries(series, 1, 1.)

					series = q.Select(ctx, false, nil, labels.MustNewMatcher(labels.MatchRegexp, "__name__", fmt.Sprintf("test_metric_%d_sum", i)))
					checkFloatSeries(series, 1, 1.)

					series = q.Select(ctx, false, nil, labels.MustNewMatcher(labels.MatchRegexp, "__name__", fmt.Sprintf("test_metric_%d_bucket", i)))
					checkFloatSeries(series, 1, 1.)

					series = q.Select(ctx, false, nil, labels.MustNewMatcher(labels.MatchRegexp, "__name__", fmt.Sprintf("test_histogram_%d_count", i)))
					checkFloatSeries(series, expectedClassicHistCount, 1.)

					series = q.Select(ctx, false, nil, labels.MustNewMatcher(labels.MatchRegexp, "__name__", fmt.Sprintf("test_histogram_%d_sum", i)))
					checkFloatSeries(series, expectedClassicHistCount, 10.)

					series = q.Select(ctx, false, nil, labels.MustNewMatcher(labels.MatchRegexp, "__name__", fmt.Sprintf("test_histogram_%d_bucket", i)))
					checkBucketValues(expectedClassicHistCount, series)

					series = q.Select(ctx, false, nil, labels.MustNewMatcher(labels.MatchRegexp, "__name__", fmt.Sprintf("test_histogram_%d", i)))

					var expectedSchema int32
					if expectCustomBuckets {
						expectedSchema = histogram.CustomBucketsSchema
					} else {
						expectedSchema = 3
					}
					checkHistSeries(series, expectedNativeHistCount, expectedSchema)
				}
			})
		}
	}
}

func TestScrapeLoopRunCreatesStaleMarkersOnFailedScrapeForTimestampedMetrics(t *testing.T) {
	appender := &collectResultAppender{}
	var (
		signal  = make(chan struct{}, 1)
		scraper = &testScraper{}
		app     = func(ctx context.Context) storage.Appender { return appender }
	)

	ctx, cancel := context.WithCancel(context.Background())
	// Since we're writing samples directly below we need to provide a protocol fallback.
	sl := newBasicScrapeLoopWithFallback(t, ctx, scraper, app, 10*time.Millisecond, "text/plain")
	sl.trackTimestampsStaleness = true
	// Succeed once, several failures, then stop.
	numScrapes := 0

	scraper.scrapeFunc = func(ctx context.Context, w io.Writer) error {
		numScrapes++

		switch numScrapes {
		case 1:
			w.Write([]byte(fmt.Sprintf("metric_a 42 %d\n", time.Now().UnixNano()/int64(time.Millisecond))))
			return nil
		case 5:
			cancel()
		}
		return errors.New("scrape failed")
	}

	go func() {
		sl.run(nil)
		signal <- struct{}{}
	}()

	select {
	case <-signal:
	case <-time.After(5 * time.Second):
		t.Fatalf("Scrape wasn't stopped.")
	}
	// 1 successfully scraped sample, 1 stale marker after first fail, 5 report samples for
	// each scrape successful or not.
	require.Len(t, appender.resultFloats, 27, "Appended samples not as expected:\n%s", appender)
	require.Equal(t, 42.0, appender.resultFloats[0].f, "Appended first sample not as expected")
	require.True(t, value.IsStaleNaN(appender.resultFloats[6].f),
		"Appended second sample not as expected. Wanted: stale NaN Got: %x", math.Float64bits(appender.resultFloats[6].f))
}

func TestScrapeLoopCompression(t *testing.T) {
	simpleStorage := teststorage.New(t)
	defer simpleStorage.Close()

	metricsText := makeTestMetrics(10)

	for _, tc := range []struct {
		enableCompression bool
		acceptEncoding    string
	}{
		{
			enableCompression: true,
			acceptEncoding:    "gzip",
		},
		{
			enableCompression: false,
			acceptEncoding:    "identity",
		},
	} {
		t.Run(fmt.Sprintf("compression=%v,acceptEncoding=%s", tc.enableCompression, tc.acceptEncoding), func(t *testing.T) {
			scraped := make(chan bool)

			ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
				require.Equal(t, tc.acceptEncoding, r.Header.Get("Accept-Encoding"), "invalid value of the Accept-Encoding header")
				fmt.Fprint(w, metricsText)
				close(scraped)
			}))
			defer ts.Close()

			config := &config.ScrapeConfig{
				JobName:           "test",
				SampleLimit:       100,
				Scheme:            "http",
				ScrapeInterval:    model.Duration(100 * time.Millisecond),
				ScrapeTimeout:     model.Duration(100 * time.Millisecond),
				EnableCompression: tc.enableCompression,
			}

			sp, err := newScrapePool(config, simpleStorage, 0, nil, nil, &Options{}, newTestScrapeMetrics(t))
			require.NoError(t, err)
			defer sp.stop()

			testURL, err := url.Parse(ts.URL)
			require.NoError(t, err)
			sp.Sync([]*targetgroup.Group{
				{
					Targets: []model.LabelSet{{model.AddressLabel: model.LabelValue(testURL.Host)}},
				},
			})
			require.Len(t, sp.ActiveTargets(), 1)

			select {
			case <-time.After(5 * time.Second):
				t.Fatalf("target was not scraped")
			case <-scraped:
			}
		})
	}
}

func TestPickSchema(t *testing.T) {
	tcs := []struct {
		factor float64
		schema int32
	}{
		{
			factor: 65536,
			schema: -4,
		},
		{
			factor: 256,
			schema: -3,
		},
		{
			factor: 16,
			schema: -2,
		},
		{
			factor: 4,
			schema: -1,
		},
		{
			factor: 2,
			schema: 0,
		},
		{
			factor: 1.4,
			schema: 1,
		},
		{
			factor: 1.1,
			schema: 2,
		},
		{
			factor: 1.09,
			schema: 3,
		},
		{
			factor: 1.04,
			schema: 4,
		},
		{
			factor: 1.02,
			schema: 5,
		},
		{
			factor: 1.01,
			schema: 6,
		},
		{
			factor: 1.005,
			schema: 7,
		},
		{
			factor: 1.002,
			schema: 8,
		},
		// The default value of native_histogram_min_bucket_factor
		{
			factor: 0,
			schema: 8,
		},
	}

	for _, tc := range tcs {
		schema := pickSchema(tc.factor)
		require.Equal(t, tc.schema, schema)
	}
}

func BenchmarkTargetScraperGzip(b *testing.B) {
	scenarios := []struct {
		metricsCount int
		body         []byte
	}{
		{metricsCount: 1},
		{metricsCount: 100},
		{metricsCount: 1000},
		{metricsCount: 10000},
		{metricsCount: 100000},
	}

	for i := 0; i < len(scenarios); i++ {
		var buf bytes.Buffer
		var name string
		gw := gzip.NewWriter(&buf)
		for j := 0; j < scenarios[i].metricsCount; j++ {
			name = fmt.Sprintf("go_memstats_alloc_bytes_total_%d", j)
			fmt.Fprintf(gw, "# HELP %s Total number of bytes allocated, even if freed.\n", name)
			fmt.Fprintf(gw, "# TYPE %s counter\n", name)
			fmt.Fprintf(gw, "%s %d\n", name, i*j)
		}
		gw.Close()
		scenarios[i].body = buf.Bytes()
	}

	handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("Content-Type", `text/plain; version=0.0.4`)
		w.Header().Set("Content-Encoding", "gzip")
		for _, scenario := range scenarios {
			if strconv.Itoa(scenario.metricsCount) == r.URL.Query()["count"][0] {
				w.Write(scenario.body)
				return
			}
		}
		w.WriteHeader(http.StatusBadRequest)
	})

	server := httptest.NewServer(handler)
	defer server.Close()

	serverURL, err := url.Parse(server.URL)
	if err != nil {
		panic(err)
	}

	client, err := config_util.NewClientFromConfig(config_util.DefaultHTTPClientConfig, "test_job")
	if err != nil {
		panic(err)
	}

	for _, scenario := range scenarios {
		b.Run(fmt.Sprintf("metrics=%d", scenario.metricsCount), func(b *testing.B) {
			ts := &targetScraper{
				Target: &Target{
					labels: labels.FromStrings(
						model.SchemeLabel, serverURL.Scheme,
						model.AddressLabel, serverURL.Host,
					),
					scrapeConfig: &config.ScrapeConfig{
						Params: url.Values{"count": []string{strconv.Itoa(scenario.metricsCount)}},
					},
				},
				client:  client,
				timeout: time.Second,
			}
			b.ResetTimer()
			for i := 0; i < b.N; i++ {
				_, err = ts.scrape(context.Background())
				require.NoError(b, err)
			}
		})
	}
}

// When a scrape contains multiple instances for the same time series we should increment
// prometheus_target_scrapes_sample_duplicate_timestamp_total metric.
func TestScrapeLoopSeriesAddedDuplicates(t *testing.T) {
	ctx, sl := simpleTestScrapeLoop(t)

	slApp := sl.appender(ctx)
	total, added, seriesAdded, err := sl.append(slApp, []byte("test_metric 1\ntest_metric 2\ntest_metric 3\n"), "text/plain", time.Time{})
	require.NoError(t, err)
	require.NoError(t, slApp.Commit())
	require.Equal(t, 3, total)
	require.Equal(t, 3, added)
	require.Equal(t, 1, seriesAdded)
	require.Equal(t, 2.0, prom_testutil.ToFloat64(sl.metrics.targetScrapeSampleDuplicate))

	slApp = sl.appender(ctx)
	total, added, seriesAdded, err = sl.append(slApp, []byte("test_metric 1\ntest_metric 1\ntest_metric 1\n"), "text/plain", time.Time{})
	require.NoError(t, err)
	require.NoError(t, slApp.Commit())
	require.Equal(t, 3, total)
	require.Equal(t, 3, added)
	require.Equal(t, 0, seriesAdded)
	require.Equal(t, 4.0, prom_testutil.ToFloat64(sl.metrics.targetScrapeSampleDuplicate))

	// When different timestamps are supplied, multiple samples are accepted.
	slApp = sl.appender(ctx)
	total, added, seriesAdded, err = sl.append(slApp, []byte("test_metric 1 1001\ntest_metric 1 1002\ntest_metric 1 1003\n"), "text/plain", time.Time{})
	require.NoError(t, err)
	require.NoError(t, slApp.Commit())
	require.Equal(t, 3, total)
	require.Equal(t, 3, added)
	require.Equal(t, 0, seriesAdded)
	// Metric is not higher than last time.
	require.Equal(t, 4.0, prom_testutil.ToFloat64(sl.metrics.targetScrapeSampleDuplicate))
}

// This tests running a full scrape loop and checking that the scrape option
// `native_histogram_min_bucket_factor` is used correctly.
func TestNativeHistogramMaxSchemaSet(t *testing.T) {
	testcases := map[string]struct {
		minBucketFactor string
		expectedSchema  int32
	}{
		"min factor not specified": {
			minBucketFactor: "",
			expectedSchema:  3, // Factor 1.09.
		},
		"min factor 1": {
			minBucketFactor: "native_histogram_min_bucket_factor: 1",
			expectedSchema:  3, // Factor 1.09.
		},
		"min factor 2": {
			minBucketFactor: "native_histogram_min_bucket_factor: 2",
			expectedSchema:  0, // Factor 2.00.
		},
	}
	for name, tc := range testcases {
		tc := tc
		t.Run(name, func(t *testing.T) {
			t.Parallel()
			testNativeHistogramMaxSchemaSet(t, tc.minBucketFactor, tc.expectedSchema)
		})
	}
}

func testNativeHistogramMaxSchemaSet(t *testing.T, minBucketFactor string, expectedSchema int32) {
	// Create a ProtoBuf message to serve as a Prometheus metric.
	nativeHistogram := prometheus.NewHistogram(
		prometheus.HistogramOpts{
			Namespace:                      "testing",
			Name:                           "example_native_histogram",
			Help:                           "This is used for testing",
			NativeHistogramBucketFactor:    1.1,
			NativeHistogramMaxBucketNumber: 100,
		},
	)
	registry := prometheus.NewRegistry()
	registry.Register(nativeHistogram)
	nativeHistogram.Observe(1.0)
	nativeHistogram.Observe(1.0)
	nativeHistogram.Observe(1.0)
	nativeHistogram.Observe(10.0) // in different bucket since > 1*1.1.
	nativeHistogram.Observe(10.0)

	gathered, err := registry.Gather()
	require.NoError(t, err)
	require.NotEmpty(t, gathered)

	histogramMetricFamily := gathered[0]
	buffer := protoMarshalDelimited(t, histogramMetricFamily)

	// Create a HTTP server to serve /metrics via ProtoBuf
	metricsServer := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("Content-Type", `application/vnd.google.protobuf; proto=io.prometheus.client.MetricFamily; encoding=delimited`)
		w.Write(buffer)
	}))
	defer metricsServer.Close()

	// Create a scrape loop with the HTTP server as the target.
	configStr := fmt.Sprintf(`
global:
  metric_name_validation_scheme: legacy
  scrape_interval: 50ms
  scrape_timeout: 25ms
scrape_configs:
  - job_name: test
    %s
    static_configs:
      - targets: [%s]
`, minBucketFactor, strings.ReplaceAll(metricsServer.URL, "http://", ""))

	s := teststorage.New(t)
	defer s.Close()
	s.DB.EnableNativeHistograms()
	reg := prometheus.NewRegistry()

	mng, err := NewManager(&Options{DiscoveryReloadInterval: model.Duration(10 * time.Millisecond), EnableNativeHistogramsIngestion: true}, nil, nil, s, reg)
	require.NoError(t, err)
	cfg, err := config.Load(configStr, promslog.NewNopLogger())
	require.NoError(t, err)
	mng.ApplyConfig(cfg)
	tsets := make(chan map[string][]*targetgroup.Group)
	go func() {
		err = mng.Run(tsets)
		require.NoError(t, err)
	}()
	defer mng.Stop()

	// Get the static targets and apply them to the scrape manager.
	require.Len(t, cfg.ScrapeConfigs, 1)
	scrapeCfg := cfg.ScrapeConfigs[0]
	require.Len(t, scrapeCfg.ServiceDiscoveryConfigs, 1)
	staticDiscovery, ok := scrapeCfg.ServiceDiscoveryConfigs[0].(discovery.StaticConfig)
	require.True(t, ok)
	require.Len(t, staticDiscovery, 1)
	tsets <- map[string][]*targetgroup.Group{"test": staticDiscovery}

	// Wait for the scrape loop to scrape the target.
	require.Eventually(t, func() bool {
		q, err := s.Querier(0, math.MaxInt64)
		require.NoError(t, err)
		seriesS := q.Select(context.Background(), false, nil, labels.MustNewMatcher(labels.MatchEqual, "__name__", "testing_example_native_histogram"))
		countSeries := 0
		for seriesS.Next() {
			countSeries++
		}
		return countSeries > 0
	}, 5*time.Second, 100*time.Millisecond)

	// Check that native histogram schema is as expected.
	q, err := s.Querier(0, math.MaxInt64)
	require.NoError(t, err)
	seriesS := q.Select(context.Background(), false, nil, labels.MustNewMatcher(labels.MatchEqual, "__name__", "testing_example_native_histogram"))
	histogramSamples := []*histogram.Histogram{}
	for seriesS.Next() {
		series := seriesS.At()
		it := series.Iterator(nil)
		for vt := it.Next(); vt != chunkenc.ValNone; vt = it.Next() {
			if vt != chunkenc.ValHistogram {
				// don't care about other samples
				continue
			}
			_, h := it.AtHistogram(nil)
			histogramSamples = append(histogramSamples, h)
		}
	}
	require.NoError(t, seriesS.Err())
	require.NotEmpty(t, histogramSamples)
	for _, h := range histogramSamples {
		require.Equal(t, expectedSchema, h.Schema)
	}
}

func TestTargetScrapeConfigWithLabels(t *testing.T) {
	const (
		configTimeout        = 1500 * time.Millisecond
		expectedTimeout      = "1.5"
		expectedTimeoutLabel = "1s500ms"
		secondTimeout        = 500 * time.Millisecond
		secondTimeoutLabel   = "500ms"
		expectedParam        = "value1"
		secondParam          = "value2"
		expectedPath         = "/metric-ok"
		secondPath           = "/metric-nok"
		httpScheme           = "http"
		paramLabel           = "__param_param"
		jobName              = "test"
	)

	createTestServer := func(t *testing.T, done chan struct{}) *url.URL {
		server := httptest.NewServer(
			http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
				defer close(done)
				require.Equal(t, expectedTimeout, r.Header.Get("X-Prometheus-Scrape-Timeout-Seconds"))
				require.Equal(t, expectedParam, r.URL.Query().Get("param"))
				require.Equal(t, expectedPath, r.URL.Path)

				w.Header().Set("Content-Type", `text/plain; version=0.0.4`)
				w.Write([]byte("metric_a 1\nmetric_b 2\n"))
			}),
		)
		t.Cleanup(server.Close)
		serverURL, err := url.Parse(server.URL)
		require.NoError(t, err)
		return serverURL
	}

	run := func(t *testing.T, cfg *config.ScrapeConfig, targets []*targetgroup.Group) chan struct{} {
		done := make(chan struct{})
		srvURL := createTestServer(t, done)

		// Update target addresses to use the dynamically created server URL.
		for _, target := range targets {
			for i := range target.Targets {
				target.Targets[i][model.AddressLabel] = model.LabelValue(srvURL.Host)
			}
		}

		sp, err := newScrapePool(cfg, &nopAppendable{}, 0, nil, nil, &Options{}, newTestScrapeMetrics(t))
		require.NoError(t, err)
		t.Cleanup(sp.stop)

		sp.Sync(targets)
		return done
	}

	cases := []struct {
		name    string
		cfg     *config.ScrapeConfig
		targets []*targetgroup.Group
	}{
		{
			name: "Everything in scrape config",
			cfg: &config.ScrapeConfig{
				ScrapeInterval: model.Duration(2 * time.Second),
				ScrapeTimeout:  model.Duration(configTimeout),
				Params:         url.Values{"param": []string{expectedParam}},
				JobName:        jobName,
				Scheme:         httpScheme,
				MetricsPath:    expectedPath,
			},
			targets: []*targetgroup.Group{
				{
					Targets: []model.LabelSet{
						{model.AddressLabel: model.LabelValue("")},
					},
				},
			},
		},
		{
			name: "Overridden in target",
			cfg: &config.ScrapeConfig{
				ScrapeInterval: model.Duration(2 * time.Second),
				ScrapeTimeout:  model.Duration(secondTimeout),
				JobName:        jobName,
				Scheme:         httpScheme,
				MetricsPath:    secondPath,
				Params:         url.Values{"param": []string{secondParam}},
			},
			targets: []*targetgroup.Group{
				{
					Targets: []model.LabelSet{
						{
							model.AddressLabel:       model.LabelValue(""),
							model.ScrapeTimeoutLabel: expectedTimeoutLabel,
							model.MetricsPathLabel:   expectedPath,
							paramLabel:               expectedParam,
						},
					},
				},
			},
		},
		{
			name: "Overridden in relabel_config",
			cfg: &config.ScrapeConfig{
				ScrapeInterval: model.Duration(2 * time.Second),
				ScrapeTimeout:  model.Duration(secondTimeout),
				JobName:        jobName,
				Scheme:         httpScheme,
				MetricsPath:    secondPath,
				Params:         url.Values{"param": []string{secondParam}},
				RelabelConfigs: []*relabel.Config{
					{
						Action:       relabel.DefaultRelabelConfig.Action,
						Regex:        relabel.DefaultRelabelConfig.Regex,
						SourceLabels: relabel.DefaultRelabelConfig.SourceLabels,
						TargetLabel:  model.ScrapeTimeoutLabel,
						Replacement:  expectedTimeoutLabel,
					},
					{
						Action:       relabel.DefaultRelabelConfig.Action,
						Regex:        relabel.DefaultRelabelConfig.Regex,
						SourceLabels: relabel.DefaultRelabelConfig.SourceLabels,
						TargetLabel:  paramLabel,
						Replacement:  expectedParam,
					},
					{
						Action:       relabel.DefaultRelabelConfig.Action,
						Regex:        relabel.DefaultRelabelConfig.Regex,
						SourceLabels: relabel.DefaultRelabelConfig.SourceLabels,
						TargetLabel:  model.MetricsPathLabel,
						Replacement:  expectedPath,
					},
				},
			},
			targets: []*targetgroup.Group{
				{
					Targets: []model.LabelSet{
						{
							model.AddressLabel:       model.LabelValue(""),
							model.ScrapeTimeoutLabel: secondTimeoutLabel,
							model.MetricsPathLabel:   secondPath,
							paramLabel:               secondParam,
						},
					},
				},
			},
		},
	}

	for _, c := range cases {
		t.Run(c.name, func(t *testing.T) {
			select {
			case <-run(t, c.cfg, c.targets):
			case <-time.After(10 * time.Second):
				t.Fatal("timeout after 10 seconds")
			}
		})
	}
}

func newScrapableServer(scrapeText string) (s *httptest.Server, scrapedTwice chan bool) {
	var scrapes int
	scrapedTwice = make(chan bool)

	return httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		fmt.Fprint(w, scrapeText)
		scrapes++
		if scrapes == 2 {
			close(scrapedTwice)
		}
	})), scrapedTwice
}

// Regression test for the panic fixed in https://github.com/prometheus/prometheus/pull/15523.
func TestScrapePoolScrapeAfterReload(t *testing.T) {
	h := httptest.NewServer(http.HandlerFunc(
		func(w http.ResponseWriter, r *http.Request) {
			w.Write([]byte{0x42, 0x42})
		},
	))
	t.Cleanup(h.Close)

	cfg := &config.ScrapeConfig{
		BodySizeLimit:     1,
		JobName:           "test",
		Scheme:            "http",
		ScrapeInterval:    model.Duration(100 * time.Millisecond),
		ScrapeTimeout:     model.Duration(100 * time.Millisecond),
		EnableCompression: false,
		ServiceDiscoveryConfigs: discovery.Configs{
			&discovery.StaticConfig{
				{
					Targets: []model.LabelSet{{model.AddressLabel: model.LabelValue(h.URL)}},
				},
			},
		},
	}

	p, err := newScrapePool(cfg, &nopAppendable{}, 0, nil, nil, &Options{}, newTestScrapeMetrics(t))
	require.NoError(t, err)
	t.Cleanup(p.stop)

	p.Sync([]*targetgroup.Group{
		{
			Targets: []model.LabelSet{{model.AddressLabel: model.LabelValue(strings.TrimPrefix(h.URL, "http://"))}},
			Source:  "test",
		},
	})

	require.NoError(t, p.reload(cfg))

	<-time.After(1 * time.Second)
}