109 lines
2.9 KiB
Go
109 lines
2.9 KiB
Go
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// Package teststat provides helpers for testing metrics backends.
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package teststat
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import (
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"errors"
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"fmt"
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"math"
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"math/rand"
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"strings"
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"github.com/go-kit/kit/metrics"
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)
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// TestCounter puts some deltas through the counter, and then calls the value
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// func to check that the counter has the correct final value.
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func TestCounter(counter metrics.Counter, value func() float64) error {
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a := rand.Perm(100)
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n := rand.Intn(len(a))
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var want float64
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for i := 0; i < n; i++ {
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f := float64(a[i])
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counter.Add(f)
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want += f
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}
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if have := value(); want != have {
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return fmt.Errorf("want %f, have %f", want, have)
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}
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return nil
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}
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// TestGauge puts some values through the gauge, and then calls the value func
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// to check that the gauge has the correct final value.
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func TestGauge(gauge metrics.Gauge, value func() float64) error {
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a := rand.Perm(100)
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n := rand.Intn(len(a))
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var want float64
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for i := 0; i < n; i++ {
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f := float64(a[i])
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gauge.Set(f)
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want = f
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}
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if have := value(); want != have {
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return fmt.Errorf("want %f, have %f", want, have)
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}
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return nil
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}
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// TestHistogram puts some observations through the histogram, and then calls
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// the quantiles func to checks that the histogram has computed the correct
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// quantiles within some tolerance
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func TestHistogram(histogram metrics.Histogram, quantiles func() (p50, p90, p95, p99 float64), tolerance float64) error {
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PopulateNormalHistogram(histogram, rand.Int())
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want50, want90, want95, want99 := normalQuantiles()
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have50, have90, have95, have99 := quantiles()
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var errs []string
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if want, have := want50, have50; !cmp(want, have, tolerance) {
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errs = append(errs, fmt.Sprintf("p50: want %f, have %f", want, have))
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}
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if want, have := want90, have90; !cmp(want, have, tolerance) {
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errs = append(errs, fmt.Sprintf("p90: want %f, have %f", want, have))
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}
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if want, have := want95, have95; !cmp(want, have, tolerance) {
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errs = append(errs, fmt.Sprintf("p95: want %f, have %f", want, have))
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}
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if want, have := want99, have99; !cmp(want, have, tolerance) {
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errs = append(errs, fmt.Sprintf("p99: want %f, have %f", want, have))
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}
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if len(errs) > 0 {
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return errors.New(strings.Join(errs, "; "))
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}
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return nil
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}
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var (
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// Count is the number of observations.
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Count = 12345
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// Mean is the center of the normal distribution of observations.
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Mean = 500
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// Stdev of the normal distribution of observations.
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Stdev = 25
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)
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// ExpectedObservationsLessThan returns the number of observations that should
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// have a value less than or equal to the given value, given a normal
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// distribution of observations described by Count, Mean, and Stdev.
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func ExpectedObservationsLessThan(bucket int64) int64 {
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// https://code.google.com/p/gostat/source/browse/stat/normal.go
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cdf := ((1.0 / 2.0) * (1 + math.Erf((float64(bucket)-float64(Mean))/(float64(Stdev)*math.Sqrt2))))
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return int64(cdf * float64(Count))
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}
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func cmp(want, have, tol float64) bool {
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if (math.Abs(want-have) / want) > tol {
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return false
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}
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return true
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}
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