DeltaCrdt

DeltaCrdt implements some Delta CRDTs in Elixir. There is an introductory blog post and the official documentation on hexdocs.pm is also very good.

CRDTs currently offered include:

• Add Wins Last Write Wins Map
• Add Wins Set

Please open an issue or a pull request if you'd like to see any additional Delta CRDTs included.

The following papers have used to implement this library:

• Delta State Replicated Data Types – Almeida et al. 2016
• Efficient Synchronization of State-based CRDTs – Enes et al. 2018

Usage

Documentation can be found on hexdocs.pm.

Here's a short example to illustrate adding an entry to a map:

# start 2 Delta CRDTs
{:ok, crdt1} = DeltaCrdt.start_link(DeltaCrdt.AWLWWMap)
{:ok, crdt2} = DeltaCrdt.start_link(DeltaCrdt.AWLWWMap)

# make them aware of each other
DeltaCrdt.add_neighbours(crdt1, [crdt2])

# show the initial value
DeltaCrdt.read(crdt1)
%{}

# add a key/value in crdt1
DeltaCrdt.mutate(crdt1, :add, ["CRDT", "is magic!"])

# read it after it has been replicated to crdt2
DeltaCrdt.read(crdt2)
%{"CRDT" => "is magic!"}

Installation

The package can be installed by adding delta_crdt to your list of dependencies in mix.exs:

def deps do
  [
    {:delta_crdt, "~> 0.3.1"}
  ]
end