eventstore

Introduction

The project goal is to provide an eventstore implementation for node.js:

• load and store events via EventStream object
• event dispatching to your publisher
• supported Dbs (MongoDb, Redis, TingoDb)
• snapshot support

Installation

npm install eventstore

choose one of the existing storage implementation or provide your own:

// for mongoDb
npm install eventstore.mongodb

// for redis
npm install eventstore.redis

// for tingoDb
npm install eventstore.tingodb

Usage

Require the module and init the eventstore:

var eventstore = require('eventstore');

var es = eventstore.createStore(); // optional pass in your options
                                 // to disable forking of event dispatching set forkDispatching to false
                                 // to disable complete event dispatching set enableDispatching to false

By default the eventstore will use an inMemory Storage, a fakePublisher and no logger.

To use the provided console.logger you could create the eventstore with option eventstore.createStore({logger: 'console'});.

Provide implementation for storage and publishing events

Example will use redis storage, but same will work for mongoDb.

var storage = require('eventstore.redis');

storage.createStorage(function(err, store) {
    es.configure(function() {
        es.use(store);
        es.use(publisher); // your publisher must provide function 'publisher.publish(event)'
        // es.use(logger);
    });

    // start eventstore
    es.start();
});

// Mongodb storage
storage.createStorage({
  host: 'localhost',
  port: 27017,
  dbName: 'eventstore',
  eventsCollectionName: 'events',
  snapshotsCollectionName: 'snapshots'
},function(err, store) {
    es.configure(function() {
        es.use(store);
        es.use(publisher); // your publisher must provide function 'publisher.publish(event)'
        // es.use(logger);
    });

    // start eventstore
    es.start();
});

Work with the eventstore

get the eventhistory of an aggregate

es.getEventStream(aggregateId, 0, function(err, stream) {
var history = stream.events; // the original event will be in events[i].payload

  // myAggregate.loadFromHistory(history);

});

store a new event and commit it to store

es.getEventStream(aggregateId, 0, function(err, stream) {                    
  stream.addEvent(new event);
  stream.commit();

});

the committed event will be dispatched to the provided publisher

Work with snapshotting

get snapshot and eventhistory from the snapshot point

es.getFromSnapshot(aggregateId, function(err, snapshot, stream) {
	
	var snap = snapshot.data;
	var history = stream.events; // events history from given snapshot

	myAggregate.loadSnapshot(snap);
	myAggregate.loadFromHistory(history);

});

create a snapshot point

es.getFromSnapshot(aggregateId, function(err, snapshot, stream) {
	
	var snap = snapshot.data;
	var history = stream.events; // events history from given snapshot

	myAggregate.loadSnapshot(snap);
	myAggregate.loadFromHistory(history);

	// create a new snapshot depending on your rules
	if (history.length > myRange) {
		es.createSnapshot(aggregateId, stream.currentRevision(), myAggregate.getSnap()[, snapshotVersion]);
	}

	// go on: store new event and commit it

});

Replaying events

If you want to replay all events from the store you can do it with the function getAllEvents:

var handle = function(err, events) {
  // events is the eventstream
  if (events.length === amount) {
    events.next(handle);
  } else {
    // finished to replay
  }
};

es.getAllEvents(0, 100, handle);

or with the function getEventRange:

var match = {} // match query in inner event (payload), for example: { id: eventId }
               // if {} all events will return
  , amount = 20; // amount of events to receive per request

var handle = function(err, events) {
  // events is the eventstream
  if (events.length === amount) {
    events.next(handle);
  } else {
    // finished to replay
  }
};

es.getEventRange(match, amount, handle);

If you want to replay all events of a particular aggregate or stream you can do it with the function getEvents:

var streamId = '1234'
  , revMin = null  // optional, must be a number
  , revMax = null; // optional, must be a number

es.getEvents(streamId, revMin, revMax, function(err, events) {
  // events is the eventstream
});

own event dispatching

es.getUndispatchedEvents(function(err, evts) {
	
	// all undispatched events
	console.log(evts);

	// dispatch it and set the event as dispatched
	es.setEventToDispatched(evts[0], function(err) {});

});

Sample Integration

• nodeCQRS A CQRS sample integrating eventstore

Inspiration

• Jonathan Oliver's EventStore for .net.

License

Copyright (c) 2014 Jan Muehlemann, Adriano Raiano

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.