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 on 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.
See sql_crdt for an implementation of CRDTs backed by an SQL database.
Usage
The Crdt class works as a layer on top of a map. The simplest way to experiment is to initialise it with 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.
Features and bugs
Please file feature requests and bugs at the issue tracker.