# DeltaCrdt

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DeltaCrdt implements a key/value store using concepts from Delta CRDTs, and relies on [`MerkleMap`]( for efficient synchronization.

There is a (slightly out of date) [introductory blog post]( and the (very much up to date) official documentation on []( is also very good.

The following papers have been 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 [](

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.set_neighbours(crdt1, [crdt2])

# show the initial value

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

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

⚠️ **Use atoms carefully** : Any atom contained in a key or value will be replicated across all nodes, and will never be garbage collected by the BEAM.

## Telemetry metrics

DeltaCrdt publishes the metric `[:delta_crdt, :sync, :done]`.

## Installation

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

def deps do
    {:delta_crdt, "~> 0.5.0"}