58a8ce4e47
* Added weighted HRW sorting This commit proposes renaming of old `SortByWeight` functions to `Sort` and implementation of `SortByWeight` function with explicit weights in arguments. `SortByWeight` function calculates normalized hashes of nodes and normalized input weights. Then multiplies these values to obtain node's actual weight for later sorting. - renamed `SortByWeight` function to `Sort` - added `SortByWeight`, `SortSliceByWeightValue` and `SortSliceBeWeightIndex` functions - moved code with reflection processing into `prepareRule` function - added tests and benchmarks for new weighted functions - added benchmark results into README * Fixed comments
4 KiB
4 KiB
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
Benchmark:
BenchmarkSort_fnv_10-8 5000000 354 ns/op 224 B/op 3 allocs/op
BenchmarkSort_fnv_100-8 300000 5103 ns/op 1856 B/op 3 allocs/op
BenchmarkSort_fnv_1000-8 10000 115874 ns/op 16448 B/op 3 allocs/op
BenchmarkSortByIndex_fnv_10-8 3000000 562 ns/op 384 B/op 7 allocs/op
BenchmarkSortByIndex_fnv_100-8 200000 5819 ns/op 2928 B/op 7 allocs/op
BenchmarkSortByIndex_fnv_1000-8 10000 125859 ns/op 25728 B/op 7 allocs/op
BenchmarkSortByValue_fnv_10-8 2000000 1056 ns/op 544 B/op 17 allocs/op
BenchmarkSortByValue_fnv_100-8 200000 9593 ns/op 4528 B/op 107 allocs/op
BenchmarkSortByValue_fnv_1000-8 10000 109272 ns/op 41728 B/op 1007 allocs/op
BenchmarkSortByWeight_fnv_10-8 3000000 500 ns/op 320 B/op 4 allocs/op
BenchmarkSortByWeight_fnv_100-8 200000 8257 ns/op 2768 B/op 4 allocs/op
BenchmarkSortByWeight_fnv_1000-8 10000 197938 ns/op 24656 B/op 4 allocs/op
BenchmarkSortByWeightIndex_fnv_10-8 2000000 760 ns/op 480 B/op 8 allocs/op
BenchmarkSortByWeightIndex_fnv_100-8 200000 9191 ns/op 3840 B/op 8 allocs/op
BenchmarkSortByWeightIndex_fnv_1000-8 10000 208204 ns/op 33936 B/op 8 allocs/op
BenchmarkSortByWeightValue_fnv_10-8 1000000 1095 ns/op 640 B/op 18 allocs/op
BenchmarkSortByWeightValue_fnv_100-8 200000 12291 ns/op 5440 B/op 108 allocs/op
BenchmarkSortByWeightValue_fnv_1000-8 10000 145125 ns/op 49936 B/op 1008 allocs/op
Example
package main
import (
"fmt"
"github.com/nspcc-dev/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
}