Event-Sauced - Slightly opinionated multi-database Event Store

For when you need to store events... in a store... of some description

This project started out as a re-implementation of ASOS/SimpleEventStore in TypeScript. What was initially just a simple re-write, is slowly becoming a more featured library.

The goal of Event-Sauced is to be provide a database-agnostic API for an event store. It will be slightly opinionated, but only to the point of provided the right abstraction over the various databases. It operates on a couple of premises:

• Be able to get going with only the core module and the included InMemoryStorageEngine
• Be as modular as possible - no reason to pull down the aws-sdk if you are going to use PostgreSQL as a data engine
• Allow users to implement - and inject - their own data engines if so desired
• Provide data consistency and concurrency support in all supported engines

Documentation

Currently there's no documentation. That went the way of the dodo after the Github Actions and organization move. I'm currently tracking adding documentation against https://github.com/Silly-Goose-Software/event-sauced-ts/issues/411, if you're interested.

Install

With npm installed, run

npm install @silly-goose-software/event-sauced-ts

Usage

// const eventStore = require('event-sauced-ts.umd);
// or
// const {...} = require(event-sauced-ts.umd)

const e = require('../../dist/event-sauced-ts.umd');

const toEventData = (event) => new e.EventData(event.id, event)

const storageEngine = new e.InMemoryStorageEngine();
const eventStore = new e.EventStore(storageEngine);

(async function main() {
  const streamId = 'd864da7d-c879-452d-9570-fbd1ce377b86'

  const firstEvent = {
    id: 'ba6945f4-04a6-44a9-9d93-936e49cb07d3',
    type: 'UserCreated',
    firstName: 'Yannick',
    lastName: 'Meeus'
  };

  const secondEvent = {
    id: '3d5520a4-9977-4c1e-9052-52037165dfb6',
    type: 'AgeChanged',
    newAge: 35
  }

  const thirdEvent = {
    id: '7699c01f-25f9-4ab5-9f85-ac939693905e',
    type: 'JobChanged',
    newJob: 'Superhero'
  }

  const firstTwoEvents = [firstEvent, secondEvent].map(toEventData)

  // Add the first two events to the stream
  await eventStore.AppendToStream(streamId, 0, ...firstTwoEvents);

  // Retrieve the full stream
  let currentStoredEventStream = await eventStore.readStreamForwards(streamId)
  console.log(currentStoredEventStream);

  // Add the third event to the stream, notice that we have to specify where we think we are in the stream.
  // This is our concurrency check, the engine will verify this but the reason we have to be in agreement
  // with the server is to ensure we do not get a corrupt stream.
  // In practice, this would be hidden away from the consumer in the repository or what-not, but I wanted
  // to keep that kind of complexity out of this.
  await eventStore.AppendToStream(streamId, 2, toEventData(thirdEvent))

  // Lo and behold, we now have a third event in the stream
  currentStoredEventStream = await eventStore.readStreamForwards(streamId)
  console.log(currentStoredEventStream);
})();

License

MIT