mirror of
https://github.com/VictoriaMetrics/VictoriaMetrics.git
synced 2024-12-16 00:41:24 +01:00
62 lines
1.9 KiB
Markdown
62 lines
1.9 KiB
Markdown
# Jump Consistent Hash
|
|
|
|
[](https://travis-ci.org/lithammer/go-jump-consistent-hash)
|
|
[](https://godoc.org/github.com/lithammer/go-jump-consistent-hash)
|
|
|
|
Go implementation of the jump consistent hash algorithm[1] by John Lamping and Eric Veach.
|
|
|
|
[1] http://arxiv.org/pdf/1406.2294v1.pdf
|
|
|
|
## Usage
|
|
|
|
```go
|
|
import jump "github.com/lithammer/go-jump-consistent-hash"
|
|
|
|
func main() {
|
|
h := jump.Hash(256, 1024) // h = 520
|
|
}
|
|
```
|
|
|
|
Includes a helper function for using a `string` as key instead of an `uint64`. This requires a hasher that computes the string into a format accepted by `Hash()`. Such a hasher that uses [CRC-64 (ECMA)](https://en.wikipedia.org/wiki/Cyclic_redundancy_check) is also included for convenience.
|
|
|
|
```go
|
|
h := jump.HashString("127.0.0.1", 8, jump.NewCRC64()) // h = 7
|
|
```
|
|
|
|
In reality though you probably want to use a `Hasher` so you won't have to repeat the bucket size and which key hasher used. It also uses more convenient types, like `int` instead of `int32`.
|
|
|
|
```go
|
|
hasher := jump.New(8, jump.NewCRC64())
|
|
h := hasher.Hash("127.0.0.1") // h = 7
|
|
```
|
|
|
|
If you want to use your own algorithm, you must implement the `KeyHasher` interface, which is a subset of the `hash.Hash64` interface available in the standard library.
|
|
|
|
Here's an example of a custom `KeyHasher` that uses Google's [FarmHash](https://github.com/google/farmhash) algorithm (the successor of CityHash) to compute the final key.
|
|
|
|
```go
|
|
type FarmHash struct {
|
|
buf bytes.Buffer
|
|
}
|
|
|
|
func (f *FarmHash) Write(p []byte) (n int, err error) {
|
|
return f.buf.Write(p)
|
|
}
|
|
|
|
func (f *FarmHash) Reset() {
|
|
f.buf.Reset()
|
|
}
|
|
|
|
func (f *FarmHash) Sum64() uint64 {
|
|
// https://github.com/dgryski/go-farm
|
|
return farm.Hash64(f.buf.Bytes())
|
|
}
|
|
|
|
hasher := jump.New(8, &FarmHash{})
|
|
h := hasher.Hash("127.0.0.1") // h = 5
|
|
```
|
|
|
|
## License
|
|
|
|
MIT
|