forked from TrueCloudLab/hrw
92 lines
5.9 KiB
Markdown
92 lines
5.9 KiB
Markdown
# Golang HRW implementation
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[](https://travis-ci.org/nspcc-dev/hrw)
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[](https://codecov.io/gh/nspcc-dev/hrw)
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[](https://goreportcard.com/report/github.com/nspcc-dev/hrw)
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[](https://github.com/nspcc-dev/hrw)
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[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.
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## Install
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`go get github.com/nspcc-dev/hrw`
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## Benchmark:
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```
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BenchmarkSort_fnv_10-8 4812801 240.9 ns/op 216 B/op 4 allocs/op
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BenchmarkSort_fnv_100-8 434767 2600 ns/op 1848 B/op 4 allocs/op
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BenchmarkSort_fnv_1000-8 20428 66116 ns/op 16440 B/op 4 allocs/op
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BenchmarkSortByIndex_fnv_10-8 2505410 486.5 ns/op 352 B/op 7 allocs/op
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BenchmarkSortByIndex_fnv_100-8 254556 4697 ns/op 1984 B/op 7 allocs/op
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BenchmarkSortByIndex_fnv_1000-8 13581 88334 ns/op 16576 B/op 7 allocs/op
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BenchmarkSortByValue_fnv_10-8 1761030 682.1 ns/op 592 B/op 18 allocs/op
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BenchmarkSortByValue_fnv_100-8 258838 4675 ns/op 4480 B/op 108 allocs/op
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BenchmarkSortByValue_fnv_1000-8 27027 44649 ns/op 40768 B/op 1008 allocs/op
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BenchmarkSortHashersByValue_Reflection_fnv_10-8 1013560 1249 ns/op 768 B/op 29 allocs/op
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BenchmarkSortHashersByValue_Reflection_fnv_100-8 106029 11414 ns/op 6096 B/op 209 allocs/op
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BenchmarkSortHashersByValue_Reflection_fnv_1000-8 10000 108977 ns/op 56784 B/op 2009 allocs/op
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BenchmarkSortHashersByValue_Typed_fnv_10-8 1577814 700.3 ns/op 584 B/op 17 allocs/op
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BenchmarkSortHashersByValue_Typed_fnv_100-8 215938 5024 ns/op 4472 B/op 107 allocs/op
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BenchmarkSortHashersByValue_Typed_fnv_1000-8 24447 46889 ns/op 40760 B/op 1007 allocs/op
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BenchmarkSortByWeight_fnv_10-8 2924833 370.6 ns/op 448 B/op 8 allocs/op
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BenchmarkSortByWeight_fnv_100-8 816069 1516 ns/op 2896 B/op 8 allocs/op
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BenchmarkSortByWeight_fnv_1000-8 80391 17478 ns/op 24784 B/op 8 allocs/op
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BenchmarkSortByWeightIndex_fnv_10-8 1945612 550.3 ns/op 368 B/op 7 allocs/op
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BenchmarkSortByWeightIndex_fnv_100-8 140473 8084 ns/op 2000 B/op 7 allocs/op
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BenchmarkSortByWeightIndex_fnv_1000-8 5518 200949 ns/op 16592 B/op 7 allocs/op
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BenchmarkSortByWeightValue_fnv_10-8 1305580 909.8 ns/op 608 B/op 18 allocs/op
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BenchmarkSortByWeightValue_fnv_100-8 165410 6796 ns/op 4496 B/op 108 allocs/op
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BenchmarkSortByWeightValue_fnv_1000-8 17922 78555 ns/op 40784 B/op 1008 allocs/op
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BenchmarkSortHashersByWeightValueReflection_fnv_10-8 454976 2229 ns/op 784 B/op 29 allocs/op
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BenchmarkSortHashersByWeightValueReflection_fnv_100-8 76264 15332 ns/op 6112 B/op 209 allocs/op
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BenchmarkSortHashersByWeightValueReflection_fnv_1000-8 80288 13192 ns/op 6112 B/op 209 allocs/op
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BenchmarkSortHashersByWeightValueTyped_fnv_10-8 1433113 901.4 ns/op 600 B/op 17 allocs/op
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BenchmarkSortHashersByWeightValueTyped_fnv_100-8 188626 5896 ns/op 4488 B/op 107 allocs/op
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BenchmarkSortHashersByWeightValueTyped_fnv_1000-8 178131 6518 ns/op 4488 B/op 107 allocs/op
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```
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## Example
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```go
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package main
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import (
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"fmt"
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"git.frostfs.info/TrueCloudLab/hrw"
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)
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func main() {
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// given a set of servers
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servers := []string{
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"one.example.com",
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"two.example.com",
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"three.example.com",
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"four.example.com",
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"five.example.com",
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"six.example.com",
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}
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// HRW can consistently select a uniformly-distributed set of servers for
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// any given key
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var (
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key = []byte("/examples/object-key")
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h = hrw.Hash(key)
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)
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hrw.SortSliceByValue(servers, h)
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for id := range servers {
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fmt.Printf("trying GET %s%s\n", servers[id], key)
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}
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// Output:
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// trying GET three.example.com/examples/object-key
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// trying GET two.example.com/examples/object-key
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// trying GET five.example.com/examples/object-key
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// trying GET six.example.com/examples/object-key
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// trying GET one.example.com/examples/object-key
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// trying GET four.example.com/examples/object-key
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}
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```
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