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// Package teststat provides helpers for testing metrics backends.
package teststat
import (
"errors"
"fmt"
"math"
"math/rand"
"reflect"
"sort"
"strings"
"github.com/go-kit/kit/metrics"
)
// TestCounter puts some deltas through the counter, and then calls the value
// func to check that the counter has the correct final value.
func TestCounter(counter metrics.Counter, value func() float64) error {
want := FillCounter(counter)
if have := value(); want != have {
return fmt.Errorf("want %f, have %f", want, have)
}
return nil
}
// FillCounter puts some deltas through the counter and returns the total value.
func FillCounter(counter metrics.Counter) float64 {
a := rand.Perm(100)
n := rand.Intn(len(a))
var want float64
for i := 0; i < n; i++ {
f := float64(a[i])
counter.Add(f)
want += f
}
return want
}
// TestGauge puts some values through the gauge, and then calls the value func
// to check that the gauge has the correct final value.
func TestGauge(gauge metrics.Gauge, value func() []float64) error {
a := rand.Perm(100)
n := rand.Intn(len(a)) + 1
var want []float64
for i := 0; i < n; i++ {
f := float64(a[i])
gauge.Set(f)
want = append(want, f)
}
for i := 0; i < n; i++ {
f := float64(a[i])
gauge.Add(f)
want = append(want, want[len(want)-1]+f)
}
have := value()
switch len(have) {
case 0:
return fmt.Errorf("got 0 values")
case 1: // provider doesn't support multi value
if have[0] != want[len(want)-1] {
return fmt.Errorf("want %f, have %f", want, have)
}
default: // provider support multi value gauges
sort.Float64s(want)
sort.Float64s(have)
if !reflect.DeepEqual(want, have) {
return fmt.Errorf("want %f, have %f", want, have)
}
}
return nil
}
// TestHistogram puts some observations through the histogram, and then calls
// the quantiles func to checks that the histogram has computed the correct
// quantiles within some tolerance
func TestHistogram(histogram metrics.Histogram, quantiles func() (p50, p90, p95, p99 float64), tolerance float64) error {
PopulateNormalHistogram(histogram, rand.Int())
want50, want90, want95, want99 := normalQuantiles()
have50, have90, have95, have99 := quantiles()
var errs []string
if want, have := want50, have50; !cmp(want, have, tolerance) {
errs = append(errs, fmt.Sprintf("p50: want %f, have %f", want, have))
}
if want, have := want90, have90; !cmp(want, have, tolerance) {
errs = append(errs, fmt.Sprintf("p90: want %f, have %f", want, have))
}
if want, have := want95, have95; !cmp(want, have, tolerance) {
errs = append(errs, fmt.Sprintf("p95: want %f, have %f", want, have))
}
if want, have := want99, have99; !cmp(want, have, tolerance) {
errs = append(errs, fmt.Sprintf("p99: want %f, have %f", want, have))
}
if len(errs) > 0 {
return errors.New(strings.Join(errs, "; "))
}
return nil
}
var (
// Count is the number of observations.
Count = 12345
// Mean is the center of the normal distribution of observations.
Mean = 500
// Stdev of the normal distribution of observations.
Stdev = 25
)
// ExpectedObservationsLessThan returns the number of observations that should
// have a value less than or equal to the given value, given a normal
// distribution of observations described by Count, Mean, and Stdev.
func ExpectedObservationsLessThan(bucket int64) int64 {
// https://code.google.com/p/gostat/source/browse/stat/normal.go
cdf := ((1.0 / 2.0) * (1 + math.Erf((float64(bucket)-float64(Mean))/(float64(Stdev)*math.Sqrt2))))
return int64(cdf * float64(Count))
}
func cmp(want, have, tol float64) bool {
if (math.Abs(want-have) / want) > tol {
return false
}
return true
}
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