Work around Hashing and tests (#2)

* Work around Hashing and tests

* fixes

* add TravisCI

* fix lint

* so slow

* add badges

* work on README

* Improved tests and get rid of fnv (#3)
This commit is contained in:
Evgeniy Kulikov 2019-01-31 12:54:02 +03:00 committed by GitHub
parent cf9a7e5b89
commit e5d4b47881
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GPG key ID: 4AEE18F83AFDEB23
6 changed files with 376 additions and 161 deletions

16
.travis.yml Normal file
View file

@ -0,0 +1,16 @@
language: go
go:
- 1.11.x
env:
- GO111MODULE=on
install:
- go get -v golang.org/x/lint/golint
- go mod tidy -v
script:
- golint -set_exit_status ./...
- go test -race -coverprofile=coverage.txt -covermode=atomic ./...
after_success:
- bash <(curl -s https://codecov.io/bash)
matrix:
allow_failures:
- go: tip

View file

@ -1 +1,56 @@
# Golang simple HRW implementation
# Golang HRW implementation
[![Build Status](https://travis-ci.org/im-kulikov/hrw.svg?branch=master)](https://travis-ci.org/im-kulikov/hrw)
[![codecov](https://codecov.io/gh/im-kulikov/hrw/badge.svg)](https://codecov.io/gh/im-kulikov/hrw)
[![Report](https://goreportcard.com/badge/github.com/im-kulikov/hrw)](https://goreportcard.com/report/github.com/im-kulikov/hrw)
[![GitHub release](https://img.shields.io/github/release/im-kulikov/hrw.svg)](https://github.com/im-kulikov/hrw)
[Rendezvous or highest random weight](https://en.wikipedia.org/wiki/Rendezvous_hashing) (HRW) hashing is an algorithm that allows clients to achieve distributed agreement on a set of k options out of a possible set of n options. A typical application is when clients need to agree on which sites (or proxies) objects are assigned to. When k is 1, it subsumes the goals of consistent hashing, using an entirely different method.
## Install
`go get github.com/im-kulikov/hrw`
## Example
```go
package main
import (
"fmt"
"github.com/im-kulikov/hrw"
)
func main() {
// 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 = hrw.Hash(key)
)
hrw.SortSliceByValue(servers, h)
for id := range servers {
fmt.Printf("trying GET %s%s\n", servers[id], key)
}
// Output:
// trying GET four.example.com/examples/object-key
// trying GET three.example.com/examples/object-key
// trying GET one.example.com/examples/object-key
// trying GET two.example.com/examples/object-key
// trying GET six.example.com/examples/object-key
// trying GET five.example.com/examples/object-key
}
```

2
go.mod
View file

@ -1,3 +1,3 @@
module github.com/im-kulikov/hrw
require github.com/reusee/mmh3 v0.0.0-20140820141314-64b85163255b
require github.com/spaolacci/murmur3 v0.0.0-20180118202830-f09979ecbc72

4
go.sum
View file

@ -1,2 +1,2 @@
github.com/reusee/mmh3 v0.0.0-20140820141314-64b85163255b h1:GQkEnyBFqzQXb3RFqGt5z2QcBZJVQxgzXKF/sPCFh7w=
github.com/reusee/mmh3 v0.0.0-20140820141314-64b85163255b/go.mod h1:ADBBIMrt68BC/v967NyoiPZMwPVq44r8QJ5oRyXJHJs=
github.com/spaolacci/murmur3 v0.0.0-20180118202830-f09979ecbc72 h1:qLC7fQah7D6K1B0ujays3HV9gkFtllcxhzImRR7ArPQ=
github.com/spaolacci/murmur3 v0.0.0-20180118202830-f09979ecbc72/go.mod h1:JwIasOWyU6f++ZhiEuf87xNszmSA2myDM2Kzu9HwQUA=

65
hrw.go
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@ -3,16 +3,17 @@
package hrw
import (
"errors"
"hash/fnv"
"encoding/binary"
"reflect"
"sort"
"strconv"
"github.com/spaolacci/murmur3"
)
type (
swapper func(i, j int)
// Hasher interface used by SortSliceByValue
Hasher interface{ Hash() uint64 }
hashed struct {
@ -38,6 +39,12 @@ func (h hashed) Len() int { return h.length }
func (h hashed) Less(i, j int) bool { return h.weight[h.sorted[i]] < h.weight[h.sorted[j]] }
func (h hashed) Swap(i, j int) { h.sorted[i], h.sorted[j] = h.sorted[j], h.sorted[i] }
// Hash uses murmur3 hash to return uint64
func Hash(key []byte) uint64 {
return murmur3.Sum64(key)
}
// SortByWeight receive nodes and hash, and sort it by weight
func SortByWeight(nodes []uint64, hash uint64) []uint64 {
var (
l = len(nodes)
@ -57,10 +64,11 @@ func SortByWeight(nodes []uint64, hash uint64) []uint64 {
return h.sorted
}
func SortSliceByValue(slice interface{}, hash uint64) error {
// SortSliceByValue received []T and hash to sort by value-weight
func SortSliceByValue(slice interface{}, hash uint64) {
t := reflect.TypeOf(slice)
if t.Kind() != reflect.Slice {
return errors.New("must be slice")
return
}
var (
@ -71,29 +79,24 @@ func SortSliceByValue(slice interface{}, hash uint64) error {
)
if length == 0 {
return nil
return
}
switch slice := slice.(type) {
case []int:
hasher := fnv.New64()
var key = make([]byte, 16)
for i := 0; i < length; i++ {
hasher.Reset()
// error always nil
_, _ = hasher.Write([]byte(strconv.Itoa(slice[i])))
rule = append(rule, weight(hash, hasher.Sum64()))
binary.BigEndian.PutUint64(key, uint64(slice[i]))
rule = append(rule, weight(Hash(key), hash))
}
case []string:
hasher := fnv.New64()
for i := 0; i < length; i++ {
hasher.Reset()
// error always nil
_, _ = hasher.Write([]byte(slice[i]))
rule = append(rule, weight(hash, hasher.Sum64()))
rule = append(rule, weight(hash,
Hash([]byte(slice[i]))))
}
default:
if _, ok := val.Index(0).Interface().(Hasher); !ok {
return errors.New("unknown type")
return
}
for i := 0; i < length; i++ {
@ -103,36 +106,44 @@ func SortSliceByValue(slice interface{}, hash uint64) error {
}
rule = SortByWeight(rule, hash)
sortByRule(swap, uint64(length), rule)
return nil
sortByRuleInverse(swap, uint64(length), rule)
}
// SortSliceByIndex received []T and hash to sort by index-weight
func SortSliceByIndex(slice interface{}, hash uint64) {
length := uint64(reflect.ValueOf(slice).Len())
swap := reflect.Swapper(slice)
rule := make([]uint64, 0, length)
for i := uint64(0); i < length; i++ {
rule = append(rule, i)
}
rule = SortByWeight(rule, hash)
sortByRule(swap, length, rule)
sortByRuleInverse(swap, length, rule)
}
func sortByRule(swap swapper, length uint64, rule []uint64) {
func sortByRuleDirect(swap swapper, length uint64, rule []uint64) {
done := make([]bool, length)
for i := uint64(0); i < length; i++ {
if done[i] {
continue
}
done[i] = true
for j := rule[i]; !done[rule[j]]; j = rule[j] {
swap(int(i), int(j))
done[j] = true
}
}
}
func sortByRuleInverse(swap swapper, length uint64, rule []uint64) {
done := make([]bool, length)
for i := uint64(0); i < length; i++ {
if done[i] {
continue
}
for j := i; !done[rule[j]]; j = rule[j] {
swap(int(j), int(rule[j]))
done[j] = true
}
}
}

View file

@ -3,18 +3,15 @@ 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")
var testKey = []byte("0xff51afd7ed558ccd")
func Example() {
// given a set of servers
@ -31,64 +28,30 @@ func Example() {
// any given key
var (
key = []byte("/examples/object-key")
h = hash(key)
err = SortSliceByValue(servers, h)
h = Hash(key)
)
if err != nil {
panic(err)
}
SortSliceByValue(servers, h)
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 three.example.com/examples/object-key
// trying GET one.example.com/examples/object-key
// trying GET two.example.com/examples/object-key
// trying GET six.example.com/examples/object-key
// trying GET five.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
return Hash([]byte(h))
}
func TestSortSliceByIndex(t *testing.T) {
actual := []string{"a", "b", "c", "d", "e", "f"}
expect := []string{"e", "a", "c", "d", "b", "f"}
hash := hash(testKey)
expect := []string{"e", "a", "c", "f", "d", "b"}
hash := Hash(testKey)
SortSliceByIndex(actual, hash)
if !reflect.DeepEqual(actual, expect) {
t.Errorf("Was %#v, but expected %#v", actual, expect)
@ -97,60 +60,79 @@ func TestSortSliceByIndex(t *testing.T) {
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)
}
expect := []string{"d", "b", "a", "f", "c", "e"}
hash := Hash(testKey)
SortSliceByValue(actual, hash)
if !reflect.DeepEqual(actual, expect) {
t.Errorf("Was %#v, but expected %#v", actual, expect)
}
}
func TestSortByRule(t *testing.T) {
t.Run("direct", func(t *testing.T) {
// 0 1 2 3 4 5
actual := []string{"a", "b", "c", "d", "e", "f"}
// 4 2 0 5 3 1
expect := []string{"c", "f", "b", "e", "a", "d"}
rule := []uint64{4, 2, 0, 5, 3, 1}
sortByRuleDirect(
func(i, j int) { actual[i], actual[j] = actual[j], actual[i] },
6, rule)
if !reflect.DeepEqual(actual, expect) {
t.Errorf("Was %#v, but expected %#v", actual, expect)
}
})
t.Run("inverse", func(t *testing.T) {
// 0 1 2 3 4 5
actual := []string{"a", "b", "c", "d", "e", "f"}
// 4 2 0 5 3 1
expect := []string{"e", "c", "a", "f", "d", "b"}
rule := []uint64{4, 2, 0, 5, 3, 1}
sortByRuleInverse(
func(i, j int) { actual[i], actual[j] = actual[j], actual[i] },
6, rule)
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)
}
var (
actual []int
hash = Hash(testKey)
)
SortSliceByValue(actual, hash)
})
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")
}
hash := Hash(testKey)
SortSliceByValue(actual, hash)
})
t.Run("must fail for unknown type", func(t *testing.T) {
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")
expect := []byte{1, 2, 3, 4, 5}
hash := Hash(testKey)
SortSliceByValue(actual, hash)
if !reflect.DeepEqual(actual, expect) {
t.Errorf("Was %#v, but expected %#v", actual, expect)
}
})
}
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)
}
expect := []hashString{"d", "b", "a", "f", "c", "e"}
hash := Hash(testKey)
SortSliceByValue(actual, hash)
if !reflect.DeepEqual(actual, expect) {
t.Errorf("Was %#v, but expected %#v", actual, expect)
}
@ -158,14 +140,9 @@ func TestSortSliceByValueHasher(t *testing.T) {
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)
}
expect := []int{2, 3, 1, 4, 0, 5}
hash := Hash(testKey)
SortSliceByValue(actual, hash)
if !reflect.DeepEqual(actual, expect) {
t.Errorf("Was %#v, but expected %#v", actual, expect)
}
@ -173,90 +150,248 @@ func TestSortSliceByValueIntSlice(t *testing.T) {
func TestSortByWeight(t *testing.T) {
nodes := []uint64{1, 2, 3, 4, 5}
hash := mur3hash(testKey)
hash := Hash(testKey)
actual := SortByWeight(nodes, hash)
expected := []uint64{0, 1, 4, 2, 3}
expected := []uint64{3, 1, 4, 2, 0}
if !reflect.DeepEqual(actual, expected) {
t.Errorf("Was %#v, but expected %#v", actual, expected)
}
}
func TestUniformDistribution(t *testing.T) {
const (
size = 10
keys = 100000
percent = 0.03
)
// We use χ2 method to determine similarity of distribution with uniform distribution.
// χ2 = Σ((n-N)**2/N)
// https://www.medcalc.org/manual/chi-square-table.php p=0.1
var chiTable = map[int]float64{9: 14.68, 99: 117.407}
t.Run("sortByWeight", func(t *testing.T) {
var (
i uint64
size = uint64(10)
nodes = make([]uint64, 0, size)
counts = make(map[uint64]uint64)
nodes [size]uint64
counts = make(map[uint64]uint64, size)
key = make([]byte, 16)
keys = uint64(10000000)
)
for i = 0; i < size; i++ {
nodes = append(nodes, i)
nodes[i] = i
}
for i = 0; i < keys; i++ {
binary.BigEndian.PutUint64(key, i)
hash := hash(key)
counts[SortByWeight(nodes, hash)[0]]++
hash := Hash(key)
counts[SortByWeight(nodes[:], hash)[0]]++
}
mean := float64(keys) / float64(len(nodes))
delta := mean * 0.01 // 1 %
var chi2 float64
mean := float64(keys) / float64(size)
delta := mean * percent
for node, count := range counts {
d := mean - float64(count)
chi2 += math.Pow(float64(count)-mean, 2) / mean
if d > delta || (0-d) > delta {
t.Errorf(
"Node %d received %d keys, expected %v (+/- %v)",
"Node %d received %d keys, expected %.0f (+/- %.2f)",
node, count, mean, delta,
)
}
}
if chi2 > chiTable[size-1] {
t.Errorf(
"Chi2 condition for .9 is not met (expected %.2f <= %.2f)",
chi2, chiTable[size-1])
}
})
t.Run("sortByIndex", func(t *testing.T) {
var (
i uint64
a, b [size]uint64
counts = make(map[uint64]int, size)
key = make([]byte, 16)
)
for i = 0; i < size; i++ {
a[i] = i
}
for i = 0; i < keys; i++ {
copy(b[:], a[:])
binary.BigEndian.PutUint64(key, i)
hash := Hash(key)
SortSliceByIndex(b[:], hash)
counts[b[0]]++
}
var chi2 float64
mean := float64(keys) / float64(size)
delta := mean * percent
for node, count := range counts {
d := mean - float64(count)
chi2 += math.Pow(float64(count)-mean, 2) / mean
if d > delta || (0-d) > delta {
t.Errorf(
"Node %d received %d keys, expected %.0f (+/- %.2f)",
node, count, mean, delta,
)
}
}
if chi2 > chiTable[size-1] {
t.Errorf(
"Chi2 condition for .9 is not met (expected %.2f <= %.2f)",
chi2, chiTable[size-1])
}
})
t.Run("sortByValue", func(t *testing.T) {
var (
i uint64
a, b [size]int
counts = make(map[int]int, size)
key = make([]byte, 16)
)
for i = 0; i < size; i++ {
a[i] = int(i)
}
for i = 0; i < keys; i++ {
copy(b[:], a[:])
binary.BigEndian.PutUint64(key, i)
hash := Hash(key)
SortSliceByValue(b[:], hash)
counts[b[0]]++
}
var chi2 float64
mean := float64(keys) / float64(size)
delta := mean * percent
for node, count := range counts {
d := mean - float64(count)
chi2 += math.Pow(float64(count)-mean, 2) / mean
if d > delta || (0-d) > delta {
t.Errorf(
"Node %d received %d keys, expected %.0f (+/- %.2f)",
node, count, mean, delta,
)
}
}
if chi2 > chiTable[size-1] {
t.Errorf(
"Chi2 condition for .9 is not met (expected %.2f <= %.2f)",
chi2, chiTable[size-1])
}
})
t.Run("sortByStringValue", func(t *testing.T) {
var (
i uint64
a, b [size]string
counts = make(map[string]int, size)
key = make([]byte, 16)
)
for i = 0; i < size; i++ {
a[i] = strconv.FormatUint(i, 10)
}
for i = 0; i < keys; i++ {
copy(b[:], a[:])
binary.BigEndian.PutUint64(key, i)
hash := Hash(key)
SortSliceByValue(b[:], hash)
counts[b[0]]++
}
var chi2 float64
mean := float64(keys) / float64(size)
delta := mean * percent
for node, count := range counts {
d := mean - float64(count)
chi2 += math.Pow(float64(count)-mean, 2) / mean
if d > delta || (0-d) > delta {
t.Errorf(
"Node %s received %d keys, expected %.0f (+/- %.2f)",
node, count, mean, delta,
)
}
}
if chi2 > chiTable[size-1] {
t.Errorf(
"Chi2 condition for .9 is not met (expected %.2f <= %.2f)",
chi2, chiTable[size-1])
}
})
t.Run("hash collision", func(t *testing.T) {
var (
i uint64
counts = make(map[uint64]uint64)
key = make([]byte, 16)
)
for i = 0; i < keys; i++ {
binary.BigEndian.PutUint64(key, i)
hash := Hash(key)
counts[hash]++
}
for node, count := range counts {
if count > 1 {
t.Errorf("Node %d received %d keys", node, count)
}
}
})
}
func BenchmarkSortByWeight_fnv_10(b *testing.B) {
hash := hash(testKey)
hash := Hash(testKey)
_ = benchmarkSortByWeight(b, 10, hash)
}
func BenchmarkSortByWeight_fnv_100(b *testing.B) {
hash := hash(testKey)
hash := Hash(testKey)
_ = benchmarkSortByWeight(b, 100, hash)
}
func BenchmarkSortByWeight_fnv_1000(b *testing.B) {
hash := hash(testKey)
hash := Hash(testKey)
_ = benchmarkSortByWeight(b, 1000, hash)
}
func BenchmarkSortByIndex_fnv_10(b *testing.B) {
hash := hash(testKey)
hash := Hash(testKey)
benchmarkSortByIndex(b, 10, hash)
}
func BenchmarkSortByIndex_fnv_100(b *testing.B) {
hash := hash(testKey)
hash := Hash(testKey)
benchmarkSortByIndex(b, 100, hash)
}
func BenchmarkSortByIndex_fnv_1000(b *testing.B) {
hash := hash(testKey)
hash := Hash(testKey)
benchmarkSortByIndex(b, 1000, hash)
}
func BenchmarkSortByValue_fnv_10(b *testing.B) {
hash := hash(testKey)
hash := Hash(testKey)
benchmarkSortByValue(b, 10, hash)
}
func BenchmarkSortByValue_fnv_100(b *testing.B) {
hash := hash(testKey)
hash := Hash(testKey)
benchmarkSortByValue(b, 100, hash)
}
func BenchmarkSortByValue_fnv_1000(b *testing.B) {
hash := hash(testKey)
hash := Hash(testKey)
benchmarkSortByValue(b, 1000, hash)
}
@ -300,8 +435,6 @@ func benchmarkSortByValue(b *testing.B, n int, hash uint64) {
b.ReportAllocs()
for i := 0; i < b.N; i++ {
if err := SortSliceByValue(servers, hash); err != nil {
b.Fatal(err)
}
SortSliceByValue(servers, hash)
}
}