Golang HRW implementation

Rendezvous or highest random weight (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/v2

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

package main
import (
"fmt""github.com/nspcc-dev/hrw/v2"
)
typehashStringstringfunc (hhashString) Hash() uint64 {
returnhrw.WrapBytes([]byte(h)).Hash()
}
funcmain() {
// given a set of serversservers:= []hrw.Hashable{
hashString("one.example.com"),
hashString("two.example.com"),
hashString("three.example.com"),
hashString("four.example.com"),
hashString("five.example.com"),
hashString("six.example.com"),
}
// HRW can consistently select a uniformly-distributed set of servers for// any given keyvarkey= []byte("/examples/object-key")
hrw.Sort(servers, hrw.WrapBytes(key))
forid:=rangeservers {
fmt.Printf("trying GET %s%s\n", servers[id], string(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
}