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https://github.com/edwingeng/doublejump

A revamped Google's jump consistent hash
https://github.com/edwingeng/doublejump

consistent-hash consistent-hash-algorithm consistent-hashing consistent-hashing-library golang

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A revamped Google's jump consistent hash

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# Overview

Doublejump is a revamped [Google's jump](https://arxiv.org/pdf/1406.2294.pdf) consistent hash. It overcomes the shortcoming of the original design - being unable to remove nodes. Here is [how it works](https://docs.google.com/presentation/d/e/2PACX-1vTHyFGUJ5CBYxZTzToc_VKxP_Za85AeZqQMNGLXFLP1tX0f9IF_z3ys9-pyKf-Jj3iWpm7dUDDaoFyb/pub?start=false&loop=false&delayms=3000).



# Benchmark

```

Doublejump/10-nodes               49276861       22.3 ns/op        0 B/op      0 allocs/op

Doublejump/100-nodes              33304191       34.9 ns/op        0 B/op      0 allocs/op

Doublejump/1000-nodes             25261296       46.3 ns/op        0 B/op      0 allocs/op



StathatConsistent/10-nodes         4780832      273.5 ns/op       80 B/op      2 allocs/op

StathatConsistent/100-nodes        4059537      291.8 ns/op       80 B/op      2 allocs/op

StathatConsistent/1000-nodes       3132294      367.6 ns/op       80 B/op      2 allocs/op



SerialxHashring/10-nodes           2766384      455.7 ns/op      152 B/op      5 allocs/op

SerialxHashring/100-nodes          2500936      487.6 ns/op      152 B/op      5 allocs/op

SerialxHashring/1000-nodes         2254138      560.0 ns/op      152 B/op      5 allocs/op

```



# Getting Started



### V1

```shell

## If golang version <= 1.17

go get -u github.com/edwingeng/doublejump

```



### V2

```shell

## If golang version >= 1.18

go get -u github.com/edwingeng/doublejump/v2

```



# Examples



### V1

```go

// If golang version <= 1.17

import "github.com/edwingeng/doublejump"



func Example() {

    h := NewHash()

    for i := 0; i < 10; i++ {

        h.Add(fmt.Sprintf("node%d", i))

    }



    fmt.Println(h.Len())

    fmt.Println(h.LooseLen())



    fmt.Println(h.Get(1000))

    fmt.Println(h.Get(2000))

    fmt.Println(h.Get(3000))



    h.Remove("node3")

    fmt.Println(h.Len())

    fmt.Println(h.LooseLen())



    fmt.Println(h.Get(1000))

    fmt.Println(h.Get(2000))

    fmt.Println(h.Get(3000))



    // Output:

    // 10

    // 10

    // node9

    // node2

    // node3

    // 9

    // 10

    // node9

    // node2

    // node0

}

```



### V2

```go

// If golang version >= 1.18

import "github.com/edwingeng/doublejump/v2"



func Example() {

    h := NewHash[string]()

    for i := 0; i < 10; i++ {

        h.Add(fmt.Sprintf("node%d", i))

    }



    fmt.Println(h.Len())

    fmt.Println(h.LooseLen())



    fmt.Println(h.Get(1000))

    fmt.Println(h.Get(2000))

    fmt.Println(h.Get(3000))



    h.Remove("node3")

    fmt.Println(h.Len())

    fmt.Println(h.LooseLen())



    fmt.Println(h.Get(1000))

    fmt.Println(h.Get(2000))

    fmt.Println(h.Get(3000))



    // Output:

    // 10

    // 10

    // node9 true

    // node2 true

    // node3 true

    // 9

    // 10

    // node9 true

    // node2 true

    // node0 true

}

```



# Acknowledgements

The implementation of the original algorithm is credited to [dgryski](https://github.com/dgryski/go-jump).