hrw/README.md
Evgenii Stratonikov 997b540432 Move from nspcc-dev to TrueCloudLab
Signed-off-by: Evgenii Stratonikov <e.stratonikov@yadro.com>
2022-12-12 18:02:07 +03:00

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# Golang HRW implementation
[![Build Status](https://travis-ci.org/nspcc-dev/hrw.svg?branch=master)](https://travis-ci.org/nspcc-dev/hrw)
[![codecov](https://codecov.io/gh/nspcc-dev/hrw/badge.svg)](https://codecov.io/gh/nspcc-dev/hrw)
[![Report](https://goreportcard.com/badge/github.com/nspcc-dev/hrw)](https://goreportcard.com/report/github.com/nspcc-dev/hrw)
[![GitHub release](https://img.shields.io/github/release/nspcc-dev/hrw.svg)](https://github.com/nspcc-dev/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/nspcc-dev/hrw`
## Benchmark:
```
BenchmarkSort_fnv_10-8 5000000 365 ns/op 224 B/op 3 allocs/op
BenchmarkSort_fnv_100-8 300000 5261 ns/op 1856 B/op 3 allocs/op
BenchmarkSort_fnv_1000-8 10000 119462 ns/op 16448 B/op 3 allocs/op
BenchmarkSortByIndex_fnv_10-8 3000000 546 ns/op 384 B/op 7 allocs/op
BenchmarkSortByIndex_fnv_100-8 200000 5965 ns/op 2928 B/op 7 allocs/op
BenchmarkSortByIndex_fnv_1000-8 10000 127732 ns/op 25728 B/op 7 allocs/op
BenchmarkSortByValue_fnv_10-8 2000000 962 ns/op 544 B/op 17 allocs/op
BenchmarkSortByValue_fnv_100-8 200000 9604 ns/op 4528 B/op 107 allocs/op
BenchmarkSortByValue_fnv_1000-8 10000 111741 ns/op 41728 B/op 1007 allocs/op
BenchmarkSortByWeight_fnv_10-8 3000000 501 ns/op 320 B/op 4 allocs/op
BenchmarkSortByWeight_fnv_100-8 200000 8495 ns/op 2768 B/op 4 allocs/op
BenchmarkSortByWeight_fnv_1000-8 10000 197880 ns/op 24656 B/op 4 allocs/op
BenchmarkSortByWeightIndex_fnv_10-8 2000000 702 ns/op 480 B/op 8 allocs/op
BenchmarkSortByWeightIndex_fnv_100-8 200000 9338 ns/op 3840 B/op 8 allocs/op
BenchmarkSortByWeightIndex_fnv_1000-8 10000 204669 ns/op 33936 B/op 8 allocs/op
BenchmarkSortByWeightValue_fnv_10-8 1000000 1083 ns/op 640 B/op 18 allocs/op
BenchmarkSortByWeightValue_fnv_100-8 200000 11444 ns/op 5440 B/op 108 allocs/op
BenchmarkSortByWeightValue_fnv_1000-8 10000 148471 ns/op 49936 B/op 1008 allocs/op
```
## Example
```go
package main
import (
"fmt"
"github.com/TrueCloudLab/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 three.example.com/examples/object-key
// trying GET two.example.com/examples/object-key
// trying GET five.example.com/examples/object-key
// trying GET six.example.com/examples/object-key
// trying GET one.example.com/examples/object-key
// trying GET four.example.com/examples/object-key
}
```