prometheus/storage/metric/tiered_test.go

1085 lines
25 KiB
Go

// Copyright 2013 Prometheus Team
// 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 metric
import (
"math"
"sort"
"testing"
"time"
clientmodel "github.com/prometheus/client_golang/model"
"github.com/prometheus/prometheus/stats"
"github.com/prometheus/prometheus/utility/test"
)
func buildSamples(from, to clientmodel.Timestamp, interval time.Duration, m clientmodel.Metric) (v clientmodel.Samples) {
i := clientmodel.SampleValue(0)
for from.Before(to) {
v = append(v, &clientmodel.Sample{
Metric: m,
Value: i,
Timestamp: from,
})
from = from.Add(interval)
i++
}
return
}
func buildValues(firstValue clientmodel.SampleValue, from, to clientmodel.Timestamp, interval time.Duration) (v Values) {
for from.Before(to) {
v = append(v, SamplePair{
Value: firstValue,
Timestamp: from,
})
from = from.Add(interval)
firstValue++
}
return
}
func testMakeView(t test.Tester, flushToDisk bool) {
type in struct {
atTime []getValuesAtTimeOp
atInterval []getValuesAtIntervalOp
alongRange []getValuesAlongRangeOp
}
type out struct {
atTime []Values
atInterval []Values
alongRange []Values
}
metric := clientmodel.Metric{clientmodel.MetricNameLabel: "request_count"}
fingerprint := &clientmodel.Fingerprint{}
fingerprint.LoadFromMetric(metric)
var (
instant = clientmodel.TimestampFromTime(time.Date(1984, 3, 30, 0, 0, 0, 0, time.Local))
scenarios = []struct {
data clientmodel.Samples
in in
out out
diskOnly bool
}{
// No sample, but query asks for one.
{
in: in{
atTime: []getValuesAtTimeOp{
{
baseOp: baseOp{current: instant},
},
},
},
out: out{
atTime: []Values{{}},
},
},
// Single sample, query asks for exact sample time.
{
data: clientmodel.Samples{
{
Metric: metric,
Value: 0,
Timestamp: instant,
},
},
in: in{
atTime: []getValuesAtTimeOp{
{
baseOp: baseOp{current: instant},
},
},
},
out: out{
atTime: []Values{
{
{
Timestamp: instant,
Value: 0,
},
},
},
},
},
// Single sample, query time before the sample.
{
data: clientmodel.Samples{
{
Metric: metric,
Value: 0,
Timestamp: instant.Add(time.Second),
},
{
Metric: metric,
Value: 1,
Timestamp: instant.Add(time.Second * 2),
},
},
in: in{
atTime: []getValuesAtTimeOp{
{
baseOp: baseOp{current: instant},
},
},
},
out: out{
atTime: []Values{
{
{
Timestamp: instant.Add(time.Second),
Value: 0,
},
},
},
},
},
// Single sample, query time after the sample.
{
data: clientmodel.Samples{
{
Metric: metric,
Value: 0,
Timestamp: instant,
},
},
in: in{
atTime: []getValuesAtTimeOp{
{
baseOp: baseOp{current: instant.Add(time.Second)},
},
},
},
out: out{
atTime: []Values{
{
{
Timestamp: instant,
Value: 0,
},
},
},
},
},
// Two samples, query asks for first sample time.
{
data: clientmodel.Samples{
{
Metric: metric,
Value: 0,
Timestamp: instant,
},
{
Metric: metric,
Value: 1,
Timestamp: instant.Add(time.Second),
},
},
in: in{
atTime: []getValuesAtTimeOp{
{
baseOp: baseOp{current: instant},
},
},
},
out: out{
atTime: []Values{
{
{
Timestamp: instant,
Value: 0,
},
},
},
},
},
// Three samples, query asks for second sample time.
{
data: clientmodel.Samples{
{
Metric: metric,
Value: 0,
Timestamp: instant,
},
{
Metric: metric,
Value: 1,
Timestamp: instant.Add(time.Second),
},
{
Metric: metric,
Value: 2,
Timestamp: instant.Add(time.Second * 2),
},
},
in: in{
atTime: []getValuesAtTimeOp{
{
baseOp: baseOp{current: instant.Add(time.Second)},
},
},
},
out: out{
atTime: []Values{
{
{
Timestamp: instant.Add(time.Second),
Value: 1,
},
},
},
},
},
// Three samples, query asks for time between first and second samples.
{
data: clientmodel.Samples{
{
Metric: metric,
Value: 0,
Timestamp: instant,
},
{
Metric: metric,
Value: 1,
Timestamp: instant.Add(time.Second * 2),
},
{
Metric: metric,
Value: 2,
Timestamp: instant.Add(time.Second * 4),
},
},
in: in{
atTime: []getValuesAtTimeOp{
{
baseOp: baseOp{current: instant.Add(time.Second)},
},
},
},
out: out{
atTime: []Values{
{
{
Timestamp: instant,
Value: 0,
},
{
Timestamp: instant.Add(time.Second * 2),
Value: 1,
},
},
},
},
},
// Three samples, query asks for time between second and third samples.
{
data: clientmodel.Samples{
{
Metric: metric,
Value: 0,
Timestamp: instant,
},
{
Metric: metric,
Value: 1,
Timestamp: instant.Add(time.Second * 2),
},
{
Metric: metric,
Value: 2,
Timestamp: instant.Add(time.Second * 4),
},
},
in: in{
atTime: []getValuesAtTimeOp{
{
baseOp: baseOp{current: instant.Add(time.Second * 3)},
},
},
},
out: out{
atTime: []Values{
{
{
Timestamp: instant.Add(time.Second * 2),
Value: 1,
},
{
Timestamp: instant.Add(time.Second * 4),
Value: 2,
},
},
},
},
},
// Two chunks of samples, query asks for values from second chunk.
{
data: buildSamples(
instant,
instant.Add(time.Duration(*leveldbChunkSize*4)*time.Second),
2*time.Second,
metric,
),
in: in{
atTime: []getValuesAtTimeOp{
{
baseOp: baseOp{current: instant.Add(time.Second*time.Duration(*leveldbChunkSize*2) + clientmodel.MinimumTick)},
},
},
},
out: out{
atTime: []Values{
{
{
Timestamp: instant.Add(time.Second * time.Duration(*leveldbChunkSize*2)),
Value: 200,
},
{
Timestamp: instant.Add(time.Second * (time.Duration(*leveldbChunkSize*2) + 2)),
Value: 201,
},
},
},
},
},
// Two chunks of samples, query asks for values between both chunks.
{
data: buildSamples(
instant,
instant.Add(time.Duration(*leveldbChunkSize*4)*time.Second),
2*time.Second,
metric,
),
in: in{
atTime: []getValuesAtTimeOp{
{
baseOp: baseOp{current: instant.Add(time.Second*time.Duration(*leveldbChunkSize*2) - clientmodel.MinimumTick)},
},
},
},
out: out{
atTime: []Values{
{
{
Timestamp: instant.Add(time.Second * (time.Duration(*leveldbChunkSize*2) - 2)),
Value: 199,
},
{
Timestamp: instant.Add(time.Second * time.Duration(*leveldbChunkSize*2)),
Value: 200,
},
},
},
},
},
// Two chunks of samples, getValuesAtIntervalOp spanning both.
{
data: buildSamples(
instant,
instant.Add(time.Duration(*leveldbChunkSize*6)*time.Second),
2*time.Second,
metric,
),
in: in{
atInterval: []getValuesAtIntervalOp{
{
getValuesAlongRangeOp: getValuesAlongRangeOp{
baseOp: baseOp{current: instant.Add(time.Second*time.Duration(*leveldbChunkSize*2-4) - clientmodel.MinimumTick)},
through: instant.Add(time.Second*time.Duration(*leveldbChunkSize*2+4) + clientmodel.MinimumTick),
},
interval: time.Second * 6,
},
},
},
out: out{
atInterval: []Values{
{
{
Timestamp: instant.Add(time.Second * time.Duration(*leveldbChunkSize*2-6)),
Value: 197,
},
{
Timestamp: instant.Add(time.Second * time.Duration(*leveldbChunkSize*2-4)),
Value: 198,
},
{
Timestamp: instant.Add(time.Second * time.Duration(*leveldbChunkSize*2)),
Value: 200,
},
{
Timestamp: instant.Add(time.Second * time.Duration(*leveldbChunkSize*2+2)),
Value: 201,
},
},
},
},
},
// Three chunks of samples, getValuesAlongRangeOp spanning all of them.
{
data: buildSamples(
instant,
instant.Add(time.Duration(*leveldbChunkSize*6)*time.Second),
2*time.Second,
metric,
),
in: in{
alongRange: []getValuesAlongRangeOp{
{
baseOp: baseOp{current: instant.Add(time.Second*time.Duration(*leveldbChunkSize*2-4) - clientmodel.MinimumTick)},
through: instant.Add(time.Second*time.Duration(*leveldbChunkSize*4+2) + clientmodel.MinimumTick),
},
},
},
out: out{
alongRange: []Values{buildValues(
clientmodel.SampleValue(198),
instant.Add(time.Second*time.Duration(*leveldbChunkSize*2-4)),
instant.Add(time.Second*time.Duration(*leveldbChunkSize*4+2)+clientmodel.MinimumTick),
2*time.Second,
)},
},
},
// Three chunks of samples and a getValuesAlongIntervalOp with an
// interval larger than the natural sample interval, spanning the gap
// between the second and third chunks. To test two consecutive
// ExtractSamples() calls for the same op, we need three on-disk chunks,
// because the first two chunks are loaded from disk together and passed
// as one unit into ExtractSamples(). Especially, we want to test that
// the first sample of the last chunk is included in the result.
//
// This is a regression test for an interval operator advancing too far
// past the end of the currently available chunk, effectively skipping
// over a value which is only available in the next chunk passed to
// ExtractSamples().
//
// Chunk and operator layout, assuming 200 samples per chunk:
//
// Chunk 1 Chunk 2 Chunk 3
// Values: 0......199 200......399 400......599
// Times: 0......398 400......798 800......1198
// | |
// |_________ Operator _______|
// 395 399 ...... 795 799 803
{
data: buildSamples(
instant,
instant.Add(time.Duration(*leveldbChunkSize*6)*time.Second),
2*time.Second,
metric,
),
in: in{
atInterval: []getValuesAtIntervalOp{
{
getValuesAlongRangeOp: getValuesAlongRangeOp{
baseOp: baseOp{current: instant.Add(time.Second * time.Duration(*leveldbChunkSize*2-5))},
through: instant.Add(time.Second * time.Duration(*leveldbChunkSize*4+3)),
},
interval: time.Second * 4,
},
},
},
out: out{
atInterval: []Values{
// We need two overlapping buildValues() calls here since the last
// value of the second chunk is extracted twice (value 399, time
// offset 798s).
append(
// Values 197...399.
// Times 394...798.
buildValues(
clientmodel.SampleValue(197),
instant.Add(time.Second*time.Duration(*leveldbChunkSize*2-6)),
instant.Add(time.Second*time.Duration(*leveldbChunkSize*4)),
2*time.Second,
),
// Values 399...402.
// Times 798...804.
buildValues(
clientmodel.SampleValue(399),
instant.Add(time.Second*time.Duration(*leveldbChunkSize*4-2)),
instant.Add(time.Second*time.Duration(*leveldbChunkSize*4+6)),
2*time.Second,
)...,
),
},
},
// This example only works with on-disk chunks due to the repeatedly
// extracted value at the end of the second chunk.
diskOnly: true,
},
// Single sample, getValuesAtIntervalOp starting after the sample.
{
data: clientmodel.Samples{
{
Metric: metric,
Value: 0,
Timestamp: instant,
},
},
in: in{
atInterval: []getValuesAtIntervalOp{
{
getValuesAlongRangeOp: getValuesAlongRangeOp{
baseOp: baseOp{current: instant.Add(time.Second)},
through: instant.Add(time.Second * 2),
},
interval: time.Second,
},
},
},
out: out{
atInterval: []Values{
{
{
Timestamp: instant,
Value: 0,
},
},
},
},
},
// Single sample, getValuesAtIntervalOp starting before the sample.
{
data: clientmodel.Samples{
{
Metric: metric,
Value: 0,
Timestamp: instant.Add(time.Second),
},
},
in: in{
atInterval: []getValuesAtIntervalOp{
{
getValuesAlongRangeOp: getValuesAlongRangeOp{
baseOp: baseOp{current: instant},
through: instant.Add(time.Second * 2),
},
interval: time.Second,
},
},
},
out: out{
atInterval: []Values{
{
{
Timestamp: instant.Add(time.Second),
Value: 0,
},
{
Timestamp: instant.Add(time.Second),
Value: 0,
},
},
},
},
},
}
)
for i, scenario := range scenarios {
if scenario.diskOnly && !flushToDisk {
continue
}
tiered, closer := NewTestTieredStorage(t)
err := tiered.AppendSamples(scenario.data)
if err != nil {
t.Fatalf("%d. failed to add fixture data: %s", i, err)
}
if flushToDisk {
tiered.Flush()
}
requestBuilder := NewViewRequestBuilder()
for _, atTime := range scenario.in.atTime {
requestBuilder.GetMetricAtTime(fingerprint, atTime.current)
}
for _, atInterval := range scenario.in.atInterval {
requestBuilder.GetMetricAtInterval(fingerprint, atInterval.current, atInterval.through, atInterval.interval)
}
for _, alongRange := range scenario.in.alongRange {
requestBuilder.GetMetricRange(fingerprint, alongRange.current, alongRange.through)
}
v, err := tiered.MakeView(requestBuilder, time.Second*5, stats.NewTimerGroup())
if err != nil {
t.Fatalf("%d. failed due to %s", i, err)
}
// To get all values in the View, ask for the 'forever' interval.
interval := Interval{OldestInclusive: math.MinInt64, NewestInclusive: math.MaxInt64}
for j, atTime := range scenario.out.atTime {
actual := v.GetRangeValues(fingerprint, interval)
if len(actual) != len(atTime) {
t.Fatalf("%d.%d. expected %d output, got %d", i, j, len(atTime), len(actual))
}
for k, value := range atTime {
if value.Value != actual[k].Value {
t.Errorf("%d.%d.%d expected %v value, got %v", i, j, k, value.Value, actual[k].Value)
}
if !value.Timestamp.Equal(actual[k].Timestamp) {
t.Errorf("%d.%d.%d expected %s (offset %ss) timestamp, got %s (offset %ss)", i, j, k, value.Timestamp, value.Timestamp.Sub(instant), actual[k].Timestamp, actual[k].Timestamp.Sub(instant))
}
}
}
for j, atInterval := range scenario.out.atInterval {
actual := v.GetRangeValues(fingerprint, interval)
if len(actual) != len(atInterval) {
t.Fatalf("%d.%d. expected %d output, got %d", i, j, len(atInterval), len(actual))
}
for k, value := range atInterval {
if value.Value != actual[k].Value {
t.Errorf("%d.%d.%d expected %v value, got %v", i, j, k, value.Value, actual[k].Value)
}
if !value.Timestamp.Equal(actual[k].Timestamp) {
t.Errorf("%d.%d.%d expected %s (offset %ds) timestamp, got %s (offset %ds, value %s)", i, j, k, value.Timestamp, int(value.Timestamp.Sub(instant)/time.Second), actual[k].Timestamp, int(actual[k].Timestamp.Sub(instant)/time.Second), actual[k].Value)
}
}
}
for j, alongRange := range scenario.out.alongRange {
actual := v.GetRangeValues(fingerprint, interval)
if len(actual) != len(alongRange) {
t.Fatalf("%d.%d. expected %d output, got %d", i, j, len(alongRange), len(actual))
}
for k, value := range alongRange {
if value.Value != actual[k].Value {
t.Fatalf("%d.%d.%d expected %v value, got %v", i, j, k, value.Value, actual[k].Value)
}
if !value.Timestamp.Equal(actual[k].Timestamp) {
t.Fatalf("%d.%d.%d expected %s (offset %ss) timestamp, got %s (offset %ss)", i, j, k, value.Timestamp, value.Timestamp.Sub(instant), actual[k].Timestamp, actual[k].Timestamp.Sub(instant))
}
}
}
closer.Close()
}
}
func TestMakeViewFlush(t *testing.T) {
testMakeView(t, true)
}
func BenchmarkMakeViewFlush(b *testing.B) {
for i := 0; i < b.N; i++ {
testMakeView(b, true)
}
}
func TestMakeViewNoFlush(t *testing.T) {
testMakeView(t, false)
}
func BenchmarkMakeViewNoFlush(b *testing.B) {
for i := 0; i < b.N; i++ {
testMakeView(b, false)
}
}
func TestGetAllValuesForLabel(t *testing.T) {
type in struct {
metricName string
appendToMemory bool
appendToDisk bool
}
scenarios := []struct {
in []in
out []string
}{
{
// Empty case.
}, {
in: []in{
{
metricName: "request_count",
appendToMemory: false,
appendToDisk: true,
},
},
out: []string{
"request_count",
},
}, {
in: []in{
{
metricName: "request_count",
appendToMemory: true,
appendToDisk: false,
},
{
metricName: "start_time",
appendToMemory: false,
appendToDisk: true,
},
},
out: []string{
"request_count",
"start_time",
},
}, {
in: []in{
{
metricName: "request_count",
appendToMemory: true,
appendToDisk: true,
},
{
metricName: "start_time",
appendToMemory: true,
appendToDisk: true,
},
},
out: []string{
"request_count",
"start_time",
},
},
}
for i, scenario := range scenarios {
tiered, closer := NewTestTieredStorage(t)
for j, metric := range scenario.in {
sample := &clientmodel.Sample{
Metric: clientmodel.Metric{clientmodel.MetricNameLabel: clientmodel.LabelValue(metric.metricName)},
}
if metric.appendToMemory {
if err := tiered.memoryArena.AppendSample(sample); err != nil {
t.Fatalf("%d.%d. failed to add fixture data: %s", i, j, err)
}
}
if metric.appendToDisk {
if err := tiered.DiskStorage.AppendSample(sample); err != nil {
t.Fatalf("%d.%d. failed to add fixture data: %s", i, j, err)
}
}
}
metricNames, err := tiered.GetAllValuesForLabel(clientmodel.MetricNameLabel)
closer.Close()
if err != nil {
t.Fatalf("%d. Error getting metric names: %s", i, err)
}
if len(metricNames) != len(scenario.out) {
t.Fatalf("%d. Expected metric count %d, got %d", i, len(scenario.out), len(metricNames))
}
sort.Sort(metricNames)
for j, expected := range scenario.out {
if expected != string(metricNames[j]) {
t.Fatalf("%d.%d. Expected metric %s, got %s", i, j, expected, metricNames[j])
}
}
}
}
func TestGetFingerprintsForLabelMatchers(t *testing.T) {
tiered, closer := NewTestTieredStorage(t)
defer closer.Close()
memorySample := &clientmodel.Sample{
Metric: clientmodel.Metric{clientmodel.MetricNameLabel: "http_requests", "method": "/foo"},
}
diskSample := &clientmodel.Sample{
Metric: clientmodel.Metric{clientmodel.MetricNameLabel: "http_requests", "method": "/bar"},
}
if err := tiered.memoryArena.AppendSample(memorySample); err != nil {
t.Fatalf("Failed to add fixture data: %s", err)
}
if err := tiered.DiskStorage.AppendSample(diskSample); err != nil {
t.Fatalf("Failed to add fixture data: %s", err)
}
tiered.Flush()
scenarios := []struct {
matchers LabelMatchers
fpCount int
}{
{
matchers: LabelMatchers{},
fpCount: 0,
}, {
matchers: LabelMatchers{
{
Type: Equal,
Name: clientmodel.MetricNameLabel,
Value: "http_requests",
},
},
fpCount: 2,
}, {
matchers: LabelMatchers{
{
Type: Equal,
Name: clientmodel.MetricNameLabel,
Value: "http_requests",
}, {
Type: Equal,
Name: "method",
Value: "/foo",
},
},
fpCount: 1,
}, {
matchers: LabelMatchers{
{
Type: Equal,
Name: clientmodel.MetricNameLabel,
Value: "http_requests",
}, {
Type: Equal,
Name: "method",
Value: "/bar",
},
},
fpCount: 1,
}, {
matchers: LabelMatchers{
{
Type: Equal,
Name: clientmodel.MetricNameLabel,
Value: "http_requests",
}, {
Type: Equal,
Name: "method",
Value: "/baz",
},
},
fpCount: 0,
},
}
for i, scenario := range scenarios {
fingerprints, err := tiered.GetFingerprintsForLabelMatchers(scenario.matchers)
if err != nil {
t.Fatalf("%d. Error getting metric names: %s", i, err)
}
if len(fingerprints) != scenario.fpCount {
t.Fatalf("%d. Expected metric count %d, got %d", i, scenario.fpCount, len(fingerprints))
}
}
}
func TestTruncateBefore(t *testing.T) {
type in struct {
values Values
time clientmodel.Timestamp
}
instant := clientmodel.Now()
var scenarios = []struct {
in in
out Values
}{
{
in: in{
time: instant,
values: Values{
{
Value: 0,
Timestamp: instant,
},
{
Value: 1,
Timestamp: instant.Add(time.Second),
},
{
Value: 2,
Timestamp: instant.Add(2 * time.Second),
},
{
Value: 3,
Timestamp: instant.Add(3 * time.Second),
},
{
Value: 4,
Timestamp: instant.Add(4 * time.Second),
},
},
},
out: Values{
{
Value: 0,
Timestamp: instant,
},
{
Value: 1,
Timestamp: instant.Add(time.Second),
},
{
Value: 2,
Timestamp: instant.Add(2 * time.Second),
},
{
Value: 3,
Timestamp: instant.Add(3 * time.Second),
},
{
Value: 4,
Timestamp: instant.Add(4 * time.Second),
},
},
},
{
in: in{
time: instant.Add(2 * time.Second),
values: Values{
{
Value: 0,
Timestamp: instant,
},
{
Value: 1,
Timestamp: instant.Add(time.Second),
},
{
Value: 2,
Timestamp: instant.Add(2 * time.Second),
},
{
Value: 3,
Timestamp: instant.Add(3 * time.Second),
},
{
Value: 4,
Timestamp: instant.Add(4 * time.Second),
},
},
},
out: Values{
{
Value: 1,
Timestamp: instant.Add(time.Second),
},
{
Value: 2,
Timestamp: instant.Add(2 * time.Second),
},
{
Value: 3,
Timestamp: instant.Add(3 * time.Second),
},
{
Value: 4,
Timestamp: instant.Add(4 * time.Second),
},
},
},
{
in: in{
time: instant.Add(5 * time.Second),
values: Values{
{
Value: 0,
Timestamp: instant,
},
{
Value: 1,
Timestamp: instant.Add(time.Second),
},
{
Value: 2,
Timestamp: instant.Add(2 * time.Second),
},
{
Value: 3,
Timestamp: instant.Add(3 * time.Second),
},
{
Value: 4,
Timestamp: instant.Add(4 * time.Second),
},
},
},
out: Values{
// Preserve the last value in case it needs to be used for the next set.
{
Value: 4,
Timestamp: instant.Add(4 * time.Second),
},
},
},
}
for i, scenario := range scenarios {
actual := chunk(scenario.in.values).TruncateBefore(scenario.in.time)
if len(actual) != len(scenario.out) {
t.Fatalf("%d. expected length of %d, got %d", i, len(scenario.out), len(actual))
}
for j, actualValue := range actual {
if !actualValue.Equal(&scenario.out[j]) {
t.Fatalf("%d.%d. expected %s, got %s", i, j, scenario.out[j], actualValue)
}
}
}
}
func TestGetMetricForFingerprintCachesCopyOfMetric(t *testing.T) {
ts, closer := NewTestTieredStorage(t)
defer closer.Close()
m := clientmodel.Metric{
clientmodel.MetricNameLabel: "testmetric",
}
samples := clientmodel.Samples{
&clientmodel.Sample{
Metric: m,
Value: 0,
Timestamp: clientmodel.Now(),
},
}
if err := ts.AppendSamples(samples); err != nil {
t.Fatal(err)
}
ts.Flush()
fp := &clientmodel.Fingerprint{}
fp.LoadFromMetric(m)
m, err := ts.GetMetricForFingerprint(fp)
if err != nil {
t.Fatal(err)
}
m[clientmodel.MetricNameLabel] = "changedmetric"
m, err = ts.GetMetricForFingerprint(fp)
if err != nil {
t.Fatal(err)
}
if m[clientmodel.MetricNameLabel] != "testmetric" {
t.Fatal("Metric name label value has changed: ", m[clientmodel.MetricNameLabel])
}
}