// Copyright 2014 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package net
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import (
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"math/rand"
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"testing"
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)
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func checkDistribution(t *testing.T, data []*SRV, margin float64) {
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sum := 0
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for _, srv := range data {
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sum += int(srv.Weight)
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}
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results := make(map[string]int)
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count := 1000
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for j := 0; j < count; j++ {
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d := make([]*SRV, len(data))
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copy(d, data)
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byPriorityWeight(d).shuffleByWeight()
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key := d[0].Target
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results[key] = results[key] + 1
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}
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actual := results[data[0].Target]
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expected := float64(count) * float64(data[0].Weight) / float64(sum)
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diff := float64(actual) - expected
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t.Logf("actual: %v diff: %v e: %v m: %v", actual, diff, expected, margin)
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if diff < 0 {
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diff = -diff
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}
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if diff > (expected * margin) {
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t.Errorf("missed target weight: expected %v, %v", expected, actual)
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}
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}
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func testUniformity(t *testing.T, size int, margin float64) {
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rand.Seed(1)
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data := make([]*SRV, size)
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for i := 0; i < size; i++ {
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data[i] = &SRV{Target: string('a' + i), Weight: 1}
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}
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checkDistribution(t, data, margin)
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}
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func TestDNSSRVUniformity(t *testing.T) {
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testUniformity(t, 2, 0.05)
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testUniformity(t, 3, 0.10)
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testUniformity(t, 10, 0.20)
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testWeighting(t, 0.05)
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}
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func testWeighting(t *testing.T, margin float64) {
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rand.Seed(1)
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data := []*SRV{
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{Target: "a", Weight: 60},
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{Target: "b", Weight: 30},
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{Target: "c", Weight: 10},
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}
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checkDistribution(t, data, margin)
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}
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func TestWeighting(t *testing.T) {
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testWeighting(t, 0.05)
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}
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