vvmap

vvmap is a Go implementation of a delta-based CRDT map as written about in “∆-CRDTs: Making δ-CRDTs Delta-Based”, “Dotted Version Vectors: Logical Clocks for Optimistic Replication”, and Tyler McMullen’s excellent talk “The Anatomy of a Distributed System”.

Usage:

package main
import (
    "fmt"
    "strings"
     "github.com/hankjacobs/vvmap"
)
func main() {
    lexicographicConflictResolver := func(key string, left, right vvmap.Record) bool {
        leftVal := left.Value.(string)
        rightVal := right.Value.(string)
        return strings.Compare(leftVal, rightVal) > 0 // choose left if lexicographically greater
    }
    alice := vvmap.New("alice", lexicographicConflictResolver)
    bob := vvmap.New("bob", lexicographicConflictResolver)
    tim := vvmap.New("tim", lexicographicConflictResolver)
    // concurrently update everyone -- causes a conflict, should all resolve to "turkey" since
    // lexicographically greatest
    alice.Set("lunch", "turkey")
    bob.Set("lunch", "ham")
    tim.Set("lunch", "chicken")
    // get records that Bob has but Alice doesn't
    delta := bob.Delta(alice.Version())
    alice.Merge(delta)
    // get records that Tim has but Alice doesn't
    delta = tim.Delta(alice.Version())
    alice.Merge(delta)
    // sync bob
    bob.Merge(alice.Delta(bob.Version())) // alice is most up-to-date so no need to sync with Tim
    // sync tim
    tim.Merge(alice.Delta(tim.Version()))
    fmt.Println("alice:", alice.Get("lunch"))
    fmt.Println("bob:", bob.Get("lunch"))
    fmt.Println("tim:", tim.Get("lunch"))
}