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 (optional)
• supported Dbs (inmemory, mongodb, redis, tingodb)
• snapshot support
• query your events

Installation

npm install eventstore

Usage

Require the module and init the eventstore:

var eventstore = require('eventstore');

var es = eventstore();

By default the eventstore will use an inmemory Storage.

Logging

For logging and debugging you can use debug by TJ Holowaychuk

simply run your process with

DEBUG=eventstore* node app.js

Provide implementation for storage

example with mongodb:

var es = require('eventstore')({
  type: 'mongodb',
  host: 'localhost',                          // optional
  port: 27017,                                // optional
  dbName: 'eventstore',                       // optional
  eventsCollectionName: 'events',             // optional
  snapshotsCollectionName: 'snapshots',       // optional
  transactionsCollectionName: 'transactions', // optional
  timeout: 10000                              // optional
  // username: 'technicalDbUser',                // optional
  // password: 'secret'                          // optional
});

example with redis:

var es = require('eventstore')({
  type: 'redis',
  host: 'localhost',                          // optional
  port: 6379,                                 // optional
  db: 0,                                      // optional
  prefix: 'eventstore',                       // optional
  eventsCollectionName: 'events',             // optional
  snapshotsCollectionName: 'snapshots',       // optional
  timeout: 10000                              // optional
  // password: 'secret'                          // optional
});

example with tingodb:

var es = require('eventstore')({
  type: 'tingodb',
  dbPath: '/path/to/my/db/file',              // optional
  eventsCollectionName: 'events',             // optional
  snapshotsCollectionName: 'snapshots',       // optional
  transactionsCollectionName: 'transactions', // optional
  timeout: 10000                              // optional
});

Built-in event publisher (optional)

if defined the eventstore will try to publish AND set event do dispatched on its own...

sync interface

es.useEventPublisher(function(evt) {
  // bus.emit('event', evt);
});

async interface

es.useEventPublisher(function(evt, callback) {
  // bus.sendAndWaitForAck('event', evt, callback);
});

catch connect ad disconnect events

es.on('connect', function() {
  console.log('storage connected');
});

es.on('disconnect', function() {
  console.log('connection to storage is gone');
});

initialize

es.init(function (err) {
  // this callback is called when all is ready...
});

// or

ex.init(); // callback is optional

working with the eventstore

get the eventhistory (of an aggregate)

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

  // myAggregate.loadFromHistory(history);
});

or

es.getEventStream({
  aggregateId: 'myAggregateId',
  aggregate: 'person',          // optional
  context: 'hr'                 // optional
}, function(err, stream) {                    
  var history = stream.events; // the original event will be in events[i].payload

  // myAggregate.loadFromHistory(history);
});

'streamId' and 'aggregateId' are the same... In ddd terms aggregate and context are just to be more precise in language. For example you can have a 'person' aggregate in the context 'human ressources' and a 'person' aggregate in the context of 'business contracts'... So you can have 2 complete different aggregate instances of 2 complete different aggregates (but perhaps with same name) in 2 complete different contexts

you can request an eventstream even by limit the query with a 'minimum revision number' and a 'maximum revision number'

var revMin = 5,
    revMax = 8; // if you omit revMax or you define it as -1 it will retrieve until the end 

es.getEventStream('streamId' || {/* query */}, revMin, revMax, 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('streamId', function(err, stream) {                    
  stream.addEvent({ my: 'event' });
  stream.addEvents([{ my: 'event2' }]);
  
  stream.commit();
  
  // or
  
  stream.commit(function(err, stream) {
    console.log(stream.eventsToDispatch); // this is an array containing all added events in this commit.
  });
});

if you defined an event publisher function the committed event will be dispatched to the provided publisher

working with snapshotting

get snapshot and eventhistory from the snapshot point

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

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

or

es.getFromSnapshot({
  aggregateId: 'myAggregateId',
  aggregate: 'person',          // optional
  context: 'hr'                 // optional
}, function(err, snapshot, stream) {
  var snap = snapshot.data;
  var history = stream.events; // events history from given snapshot

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

you can request a snapshot and an eventstream even by limit the query with a 'maximum revision number'

var revMax = 8; // if you omit revMax or you define it as -1 it will retrieve until the end 

es.getFromSnapshot('streamId' || {/* query */}, revMax, function(err, 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('streamId', 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 > myLimit) {
    es.createSnapshot({
      streamId: 'streamId',
      data: myAggregate.getSnap(),
      revision: stream.lastRevision,
      version: 1 // optional
    }, function(err) {
      // snapshot saved
    });
    
    // or
    
    es.createSnapshot({
      aggregateId: 'myAggregateId',
      aggregate: 'person',          // optional
      context: 'hr'                 // optional
      data: myAggregate.getSnap(),
      revision: stream.lastRevision,
      version: 1 // optional
    }, function(err) {
      // snapshot saved
    });
  }

  // go on: store new event and commit it
  // stream.addEvents...

});

own event dispatching (no event publisher function defined)

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

  // dispatch it and set the event as dispatched
  
  for (var e in evts) {
    var evt = evts[r];
    es.setEventToDispatched(evt, function(err) {});
    // or
    es.setEventToDispatched(evt.id, function(err) {});
  }

});

query your events

for replaying your events or for rebuilding a viewmodel or just for fun...

skip, limit always optional

var skip = 0,
    limit = 100; // if you omit limit or you define it as -1 it will retrieve until the end

es.getEvents(skip, limit, function(err, evts) {
  // if (events.length === amount) {
  //   events.next(function (err, nextEvts) {}); // just call next to retrieve the next page...
  // } else {
  //   // finished...
  // }
});

// or

es.getEvents('streamId', skip, limit, function(err, evts) {
  // if (events.length === amount) {
  //   events.next(function (err, nextEvts) {}); // just call next to retrieve the next page...
  // } else {
  //   // finished...
  // }
});

// or

es.getEvents({ // free choice (all, only context, only aggregate, only aggregateId...)
  context: 'hr',
  aggregate: 'person',
  aggregateId: 'uuid'
}, skip, limit, function(err, evts) {
  // if (events.length === amount) {
  //   events.next(function (err, nextEvts) {}); // just call next to retrieve the next page...
  // } else {
  //   // finished...
  // }
});

by revision

revMin, revMax always optional

var revMin = 5,
    revMax = 8; // if you omit revMax or you define it as -1 it will retrieve until the end 

es.getEventsByRevision('streamId', revMin, revMax, function(err, evts) {});

// or

es.getEventsByRevision({
  aggregateId: 'myAggregateId',
  aggregate: 'person',          // optional
  context: 'hr'                 // optional
}, revMin, revMax, function(err, evts) {});

obtain a new id

es.getNewId(function(err, newId) {
  if(err) {
    console.log('ohhh :-(');
    return;
  }

  console.log('the new id is: ' + newId);
});

Sample Integration

• nodeCQRS A CQRS sample integrating eventstore

Inspiration

• Jonathan Oliver's EventStore for .net.

#Release notes

Database Support

Currently these databases are supported:

1. inmemory
2. mongodb (node-mongodb-native)
3. redis (redis)
4. tingodb (tingodb)

own db implementation

You can use your own db implementation by extending this...

var Store = require('eventstore').Store,
    util = require('util'),
    _ = require('lodash');

function MyDB(options) {
  options = options || {};
  Store.call(this, options);
}

util.inherits(MyDB, Store);

_.extend(MyDB.prototype, {
  
  // ...
  
});

module.exports = MyDB;

and you can use it in this way

var es = require('eventstore)(Store);
// es.init...

License

Copyright (c) 2014 Adriano Raiano, Jan Muehlemann

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.