A Conflict-Free Replicated JSON Datatype for Haskell

crjdt-haskell provides high level interface to CRDT which is formalised in the paper by Martin Kleppmann and Alastair R. Beresford.

Example

{-# LANGUAGE OverloadedStrings #-}
module Main where

import Data.Crjdt as C

-- Original state
original :: Command ()
original = (doc .> key "key") =: "A"

-- First replica updates doc["key"] to "B"
replica1 :: Command ()
replica1 = do
  original
  (doc .> key "key") =: "B"

-- Second replica updates doc["key"] to "C"
replica2 :: Command ()
replica2 = do
  original
  (doc .> key "key") =: "C"

main :: IO ()
main = do
  -- Sync first and second replica
  (r1, r2) <- sync (1, replica1) (2, replica2)

  let replica1' = execEval 1 r1
      replica2' = execEval 2 r2

  -- Both replicas converge to: {"key": {"B", "C"}}
  print (document replica1' == document replica2') -- True

Future work

• Aeson support
• Simplify API as described in second version of the paper

LICENSE

Copyright © 2017 Amar Potghan

Distributed under BSD License.