hrw/hrw_test.go

307 lines
6.3 KiB
Go

package hrw
import (
"encoding/binary"
"fmt"
"hash/fnv"
"math"
"reflect"
"strconv"
"testing"
"github.com/reusee/mmh3"
)
type hashString string
var testKey = []byte("Golang simple HRW implementation")
func Example() {
// given a set of servers
servers := []string{
"one.example.com",
"two.example.com",
"three.example.com",
"four.example.com",
"five.example.com",
"six.example.com",
}
// HRW can consistently select a uniformly-distributed set of servers for
// any given key
var (
key = []byte("/examples/object-key")
h = hash(key)
err = SortSliceByValue(servers, h)
)
if err != nil {
panic(err)
}
for id := range servers {
fmt.Printf("trying GET %s%s\n", servers[id], key)
}
// Output:
// trying GET six.example.com/examples/object-key
// trying GET one.example.com/examples/object-key
// trying GET three.example.com/examples/object-key
// trying GET four.example.com/examples/object-key
// trying GET five.example.com/examples/object-key
// trying GET two.example.com/examples/object-key
}
func (h hashString) Hash() uint64 {
hs := fnv.New64()
// error always nil
_, _ = hs.Write([]byte(h))
return hs.Sum64() >> 1
}
func hash(key []byte) uint64 {
h := fnv.New64()
// error always nil
_, _ = h.Write(key)
return (h.Sum64() >> 1) ^ math.MaxUint64
}
func mur3hash(key []byte) uint64 {
h := mmh3.New128()
// error always nil
_, _ = h.Write(key)
var (
data = h.Sum(nil)
length = len(data)
result uint64
)
for i := 0; i < length; i++ {
result += uint64(data[i]) << uint64(length-i)
}
return result
}
func TestSortSliceByIndex(t *testing.T) {
actual := []string{"a", "b", "c", "d", "e", "f"}
expect := []string{"e", "a", "c", "d", "b", "f"}
hash := hash(testKey)
SortSliceByIndex(actual, hash)
if !reflect.DeepEqual(actual, expect) {
t.Errorf("Was %#v, but expected %#v", actual, expect)
}
}
func TestSortSliceByValue(t *testing.T) {
actual := []string{"a", "b", "c", "d", "e", "f"}
expect := []string{"e", "b", "c", "d", "f", "a"}
hash := hash(testKey)
if err := SortSliceByValue(actual, hash); err != nil {
t.Fatal(err)
}
if !reflect.DeepEqual(actual, expect) {
t.Errorf("Was %#v, but expected %#v", actual, expect)
}
}
func TestSortSliceByValueFail(t *testing.T) {
t.Run("empty slice", func(t *testing.T) {
actual := make([]int, 0)
hash := hash(testKey)
if err := SortSliceByValue(actual, hash); err != nil {
t.Fatal(err)
}
})
t.Run("must be slice", func(t *testing.T) {
actual := 10
hash := hash(testKey)
if err := SortSliceByValue(actual, hash); err == nil {
t.Fatal("must fail for bad type")
}
})
t.Run("must fail for unknown type", func(t *testing.T) {
actual := []byte{1, 2, 3, 4, 5}
hash := hash(testKey)
if err := SortSliceByValue(actual, hash); err == nil {
t.Fatal("must fail for bad type")
}
})
}
func TestSortSliceByValueHasher(t *testing.T) {
actual := []hashString{"a", "b", "c", "d", "e", "f"}
expect := []hashString{"e", "d", "c", "a", "b", "f"}
hash := hash(testKey)
if err := SortSliceByValue(actual, hash); err != nil {
t.Fatal(err)
}
if !reflect.DeepEqual(actual, expect) {
t.Errorf("Was %#v, but expected %#v", actual, expect)
}
}
func TestSortSliceByValueIntSlice(t *testing.T) {
actual := []int{0, 1, 2, 3, 4, 5}
expect := []int{2, 0, 5, 3, 4, 1}
hash := hash(testKey)
if err := SortSliceByValue(actual, hash); err != nil {
t.Fatal(err)
}
if !reflect.DeepEqual(actual, expect) {
t.Errorf("Was %#v, but expected %#v", actual, expect)
}
}
func TestSortByWeight(t *testing.T) {
nodes := []uint64{1, 2, 3, 4, 5}
hash := mur3hash(testKey)
actual := SortByWeight(nodes, hash)
expected := []uint64{0, 1, 4, 2, 3}
if !reflect.DeepEqual(actual, expected) {
t.Errorf("Was %#v, but expected %#v", actual, expected)
}
}
func TestUniformDistribution(t *testing.T) {
var (
i uint64
size = uint64(10)
nodes = make([]uint64, 0, size)
counts = make(map[uint64]uint64)
key = make([]byte, 16)
keys = uint64(10000000)
)
for i = 0; i < size; i++ {
nodes = append(nodes, i)
}
for i = 0; i < keys; i++ {
binary.BigEndian.PutUint64(key, i)
hash := hash(key)
counts[SortByWeight(nodes, hash)[0]]++
}
mean := float64(keys) / float64(len(nodes))
delta := mean * 0.01 // 1 %
for node, count := range counts {
d := mean - float64(count)
if d > delta || (0-d) > delta {
t.Errorf(
"Node %d received %d keys, expected %v (+/- %v)",
node, count, mean, delta,
)
}
}
}
func BenchmarkSortByWeight_fnv_10(b *testing.B) {
hash := hash(testKey)
_ = benchmarkSortByWeight(b, 10, hash)
}
func BenchmarkSortByWeight_fnv_100(b *testing.B) {
hash := hash(testKey)
_ = benchmarkSortByWeight(b, 100, hash)
}
func BenchmarkSortByWeight_fnv_1000(b *testing.B) {
hash := hash(testKey)
_ = benchmarkSortByWeight(b, 1000, hash)
}
func BenchmarkSortByIndex_fnv_10(b *testing.B) {
hash := hash(testKey)
benchmarkSortByIndex(b, 10, hash)
}
func BenchmarkSortByIndex_fnv_100(b *testing.B) {
hash := hash(testKey)
benchmarkSortByIndex(b, 100, hash)
}
func BenchmarkSortByIndex_fnv_1000(b *testing.B) {
hash := hash(testKey)
benchmarkSortByIndex(b, 1000, hash)
}
func BenchmarkSortByValue_fnv_10(b *testing.B) {
hash := hash(testKey)
benchmarkSortByValue(b, 10, hash)
}
func BenchmarkSortByValue_fnv_100(b *testing.B) {
hash := hash(testKey)
benchmarkSortByValue(b, 100, hash)
}
func BenchmarkSortByValue_fnv_1000(b *testing.B) {
hash := hash(testKey)
benchmarkSortByValue(b, 1000, hash)
}
func benchmarkSortByWeight(b *testing.B, n int, hash uint64) uint64 {
servers := make([]uint64, n)
for i := uint64(0); i < uint64(len(servers)); i++ {
servers[i] = i
}
b.ResetTimer()
b.ReportAllocs()
var x uint64
for i := 0; i < b.N; i++ {
x += SortByWeight(servers, hash)[0]
}
return x
}
func benchmarkSortByIndex(b *testing.B, n int, hash uint64) {
servers := make([]uint64, n)
for i := uint64(0); i < uint64(len(servers)); i++ {
servers[i] = i
}
b.ResetTimer()
b.ReportAllocs()
for i := 0; i < b.N; i++ {
SortSliceByIndex(servers, hash)
}
}
func benchmarkSortByValue(b *testing.B, n int, hash uint64) {
servers := make([]string, n)
for i := uint64(0); i < uint64(len(servers)); i++ {
servers[i] = "localhost:" + strconv.FormatUint(60000-i, 10)
}
b.ResetTimer()
b.ReportAllocs()
for i := 0; i < b.N; i++ {
if err := SortSliceByValue(servers, hash); err != nil {
b.Fatal(err)
}
}
}