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chore(metrics/prometheus): add files needed for coreth and subnet-evm
- replace `Gatherer` function with `NewGatherer` to export `gatherer` and return a concrete `*Gatherer` type - fix slice out of range bug in metrics.ResettingTimer case - change behavior to return an error if metric type is not supported - define local narrower registry interface - rework switch for metric families to be simpler
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‎metrics/prometheus/interfaces.libevm.go‎

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package prometheus
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type Registry interface {
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// Call the given function for each registered metric.
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Each(func(string, any))
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// Get the metric by the given name or nil if none is registered.
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Get(string) any
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}

‎metrics/prometheus/prometheus.libevm.go‎

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// (c) 2025, Ava Labs, Inc. All rights reserved.
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// See the file LICENSE for licensing terms.
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package prometheus
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import (
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"errors"
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"fmt"
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"sort"
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"strings"
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"github.com/prometheus/client_golang/prometheus"
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"github.com/ava-labs/libevm/metrics"
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dto "github.com/prometheus/client_model/go"
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)
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type Gatherer struct {
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registry Registry
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}
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var _ prometheus.Gatherer = (*Gatherer)(nil)
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// NewGatherer returns a gatherer using the given registry.
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// Note this gatherer implements the [prometheus.Gatherer] interface.
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func NewGatherer(registry Registry) *Gatherer {
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return &Gatherer{
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registry: registry,
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}
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}
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func (g *Gatherer) Gather() (mfs []*dto.MetricFamily, err error) {
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// Gather and pre-sort the metrics to avoid random listings
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var names []string
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g.registry.Each(func(name string, i interface{}) {
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names = append(names, name)
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})
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sort.Strings(names)
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mfs = make([]*dto.MetricFamily, 0, len(names))
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for _, name := range names {
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mf, err := metricFamily(g.registry, name)
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if errors.Is(err, errMetricSkip) {
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continue
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}
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mfs = append(mfs, mf)
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}
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return mfs, nil
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}
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var (
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errMetricSkip = errors.New("metric skipped")
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)
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func ptrTo[T any](x T) *T { return &x }
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func metricFamily(registry Registry, name string) (mf *dto.MetricFamily, err error) {
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metric := registry.Get(name)
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name = strings.ReplaceAll(name, "/", "_")
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switch m := metric.(type) {
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case metrics.Counter:
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return &dto.MetricFamily{
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Name: &name,
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Type: dto.MetricType_COUNTER.Enum(),
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Metric: []*dto.Metric{{
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Counter: &dto.Counter{
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Value: ptrTo(float64(m.Snapshot().Count())),
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},
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}},
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}, nil
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case metrics.CounterFloat64:
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return &dto.MetricFamily{
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Name: &name,
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Type: dto.MetricType_COUNTER.Enum(),
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Metric: []*dto.Metric{{
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Counter: &dto.Counter{
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Value: ptrTo(m.Snapshot().Count()),
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},
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}},
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}, nil
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case metrics.Gauge:
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return &dto.MetricFamily{
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Name: &name,
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Type: dto.MetricType_GAUGE.Enum(),
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Metric: []*dto.Metric{{
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Gauge: &dto.Gauge{
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Value: ptrTo(float64(m.Snapshot().Value())),
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},
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}},
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}, nil
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case metrics.GaugeFloat64:
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return &dto.MetricFamily{
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Name: &name,
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Type: dto.MetricType_GAUGE.Enum(),
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Metric: []*dto.Metric{{
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Gauge: &dto.Gauge{
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Value: ptrTo(m.Snapshot().Value()),
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},
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}},
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}, nil
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case metrics.Histogram:
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snapshot := m.Snapshot()
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quantiles := []float64{.5, .75, .95, .99, .999, .9999}
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thresholds := snapshot.Percentiles(quantiles)
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dtoQuantiles := make([]*dto.Quantile, len(quantiles))
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for i := range thresholds {
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dtoQuantiles[i] = &dto.Quantile{
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Quantile: ptrTo(quantiles[i]),
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Value: ptrTo(thresholds[i]),
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}
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}
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return &dto.MetricFamily{
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Name: &name,
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Type: dto.MetricType_SUMMARY.Enum(),
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Metric: []*dto.Metric{{
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Summary: &dto.Summary{
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SampleCount: ptrTo(uint64(snapshot.Count())), //nolint:gosec
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SampleSum: ptrTo(float64(snapshot.Sum())),
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Quantile: dtoQuantiles,
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},
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}},
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}, nil
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case metrics.Meter:
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return &dto.MetricFamily{
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Name: &name,
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Type: dto.MetricType_GAUGE.Enum(),
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Metric: []*dto.Metric{{
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Gauge: &dto.Gauge{
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Value: ptrTo(float64(m.Snapshot().Count())),
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},
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}},
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}, nil
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case metrics.Timer:
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snapshot := m.Snapshot()
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quantiles := []float64{.5, .75, .95, .99, .999, .9999}
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thresholds := snapshot.Percentiles(quantiles)
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dtoQuantiles := make([]*dto.Quantile, len(quantiles))
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for i := range thresholds {
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dtoQuantiles[i] = &dto.Quantile{
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Quantile: ptrTo(quantiles[i]),
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Value: ptrTo(thresholds[i]),
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}
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}
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return &dto.MetricFamily{
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Name: &name,
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Type: dto.MetricType_SUMMARY.Enum(),
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Metric: []*dto.Metric{{
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Summary: &dto.Summary{
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SampleCount: ptrTo(uint64(snapshot.Count())), //nolint:gosec
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SampleSum: ptrTo(float64(snapshot.Sum())),
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Quantile: dtoQuantiles,
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},
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}},
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}, nil
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case metrics.ResettingTimer:
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snapshot := m.Snapshot()
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if snapshot.Count() == 0 {
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return nil, fmt.Errorf("%w: resetting timer metric count is zero", errMetricSkip)
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}
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pvShortPercent := []float64{50, 95, 99}
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thresholds := snapshot.Percentiles(pvShortPercent)
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dtoQuantiles := make([]*dto.Quantile, len(pvShortPercent))
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for i := range pvShortPercent {
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dtoQuantiles[i] = &dto.Quantile{
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Quantile: ptrTo(pvShortPercent[i]),
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Value: ptrTo(thresholds[i]),
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}
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}
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return &dto.MetricFamily{
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Name: &name,
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Type: dto.MetricType_SUMMARY.Enum(),
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Metric: []*dto.Metric{{
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Summary: &dto.Summary{
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SampleCount: ptrTo(uint64(snapshot.Count())), //nolint:gosec
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// TODO: do we need to specify SampleSum here? and if so
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// what should that be?
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Quantile: dtoQuantiles,
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},
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}},
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}, nil
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default:
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return nil, fmt.Errorf("metric type is not supported: %T", metric)
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}
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}

‎metrics/prometheus/prometheus.libevm_test.go‎

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// (c) 2025, Ava Labs, Inc. All rights reserved.
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// See the file LICENSE for licensing terms.
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package prometheus
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import (
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"testing"
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"time"
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"github.com/stretchr/testify/require"
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"github.com/ava-labs/libevm/metrics"
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)
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func TestGatherer(t *testing.T) {
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registry := metrics.NewRegistry()
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counter := metrics.NewCounter()
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counter.Inc(12345)
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err := registry.Register("test/counter", counter)
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require.NoError(t, err)
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gauge := metrics.NewGauge()
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gauge.Update(23456)
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err = registry.Register("test/gauge", gauge)
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require.NoError(t, err)
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gaugeFloat64 := metrics.NewGaugeFloat64()
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gaugeFloat64.Update(34567.89)
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err = registry.Register("test/gauge_float64", gaugeFloat64)
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require.NoError(t, err)
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sample := metrics.NewUniformSample(1028)
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histogram := metrics.NewHistogram(sample)
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err = registry.Register("test/histogram", histogram)
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require.NoError(t, err)
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meter := metrics.NewMeter()
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defer meter.Stop()
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meter.Mark(9999999)
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err = registry.Register("test/meter", meter)
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require.NoError(t, err)
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timer := metrics.NewTimer()
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defer timer.Stop()
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timer.Update(20 * time.Millisecond)
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timer.Update(21 * time.Millisecond)
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timer.Update(22 * time.Millisecond)
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timer.Update(120 * time.Millisecond)
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timer.Update(23 * time.Millisecond)
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timer.Update(24 * time.Millisecond)
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err = registry.Register("test/timer", timer)
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require.NoError(t, err)
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resettingTimer := metrics.NewResettingTimer()
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resettingTimer.Update(10 * time.Millisecond)
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resettingTimer.Update(11 * time.Millisecond)
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resettingTimer.Update(12 * time.Millisecond)
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resettingTimer.Update(120 * time.Millisecond)
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resettingTimer.Update(13 * time.Millisecond)
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resettingTimer.Update(14 * time.Millisecond)
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err = registry.Register("test/resetting_timer", resettingTimer)
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require.NoError(t, err)
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err = registry.Register("test/resetting_timer_snapshot", resettingTimer.Snapshot())
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require.NoError(t, err)
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emptyResettingTimer := metrics.NewResettingTimer()
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err = registry.Register("test/empty_resetting_timer", emptyResettingTimer)
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require.NoError(t, err)
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err = registry.Register("test/empty_resetting_timer_snapshot", emptyResettingTimer.Snapshot())
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require.NoError(t, err)
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g := NewGatherer(registry)
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_, err = g.Gather()
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require.NoError(t, err)
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}

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