3dteemu / crdt

Dart implementation of Conflict-free Replicated Data Types (CRDTs)

Dart implementation of Conflict-free Replicated Data Types (CRDTs).

This project is heavily influenced by James Long's talk CRTDs for Mortals and includes a Dart-native implementation of Hybrid Local Clocks (HLC) based the paper Logical Physical Clocks and Consistent Snapshots in Globally Distributed Databases.

It has zero external dependencies, so it should run everywhere where Dart runs.

Usage

The Crdt class works as a layer on top of a map. The simplest way to experiment is to initialise it an empty map:

import 'package:crdt/crdt.dart';

void main() {
  var crdt = MapCrdt('node_id');

  // Insert a record
  crdt.put('a', 1);
  // Read the record
  print('Record: ${crdt.get('a')}');

  // Export the CRDT as Json
  final json = crdt.toJson();
  // Send to remote node
  final remoteJson = sendToRemote(json);
  // Merge remote CRDT with local
  crdt.mergeJson(remoteJson);
  // Verify updated record
  print('Record after merging: ${crdt.get('a')}');
}

// Mock sending the CRDT to a remote node and getting an updated one back
String sendToRemote(String json) {
  final hlc = Hlc.now('another_nodeId');
  return '{"a":{"hlc":"$hlc","value":2}}';
}

You'll probably want to implement some sort of persistent storage by subclassing the Crdt class. An example using Hive is provided in hive_crdt.

Example

A simple example is provided with this project, otherwise for a real-world application check the tudo to-do app: client & server.

Features and bugs

Please file feature requests and bugs at the issue tracker.

Testing

dart test

JavaScript version:

dart test --platform node