Quite basic and simple Event Store abstraction layer

Event store layer to help us - Cocoders to implement event sourcing in our projects. It is quite simple (or event stupid) abstraction layer (yunno KISS)

Requirements

PHP >= 7.0

Installation

Package can be installed using composer composer require cocoders/event-store Usage

Library provides bunch of interfaces and about 5 concrete classes for handling domain events.

What you need to do in order to setup this event store with your project? Follow those 5 steps.

1. Step 1 - define you aggregate In your aggregate you need implement Cocoders\EventStore\AggregateRoot interface (you can use Cocoders\EventStore\AggregateRootBehavior trait if tou want). Example: Example Domain Invoice Aggregate

2. Step 2 - define own events and use it in aggregate You should define new event classes and use those events in you aggregate

   • Example of using events in Invoice
   • Example of event class

3. Step 3 - implement own EventStore You need to create concrete implementation of Cocoders\EventStore\EventStore interface, using your favorite db engine ;) Example: Json File EventStore

4. Step 4 - do some operation on aggregate and add fresh events from Aggregate to event store, and commit event store.

Examples:

    $eventStore = new MyEventStore();
    $invoice = Invoice::issueInvoice(
        Invoice\Id::generate();
        $command->getSeller(),
        $command->getBuyer(),
        $command->maxItemNumber
    );
    $eventStore->apply(new EventStream\Name(Invoice::class), $invoice->getRecordedEvents());
    $eventStore->commit();

• Execute logic on aggregate
• Apply using repository pattern
• Commit using command bus middleware

5. Step 5 - define own projections. As you can see in example, invoice aggregate does not have many "getters". You should generate read model using projection instead of using getters. Projection is basically event subscriber which can react to event by chaging read model. To use event subscriber you need to use EventBus:

  $eventStore = new MyEventStore(); 
  $eventSubscribers = new EventSubscribers();
  $eventBus = new EventBus($eventSubscribers);
  $projectionManager = new ProjectionManager($eventSubscribers);
  $projectionManager->registerProjection(
      'InvoiceIssued',
      new MyProjection()
  );
  $newEventsStream = $eventStore->findUncommited(new EventStream\Name(Invoice::class));
  $eventStore->commit();
  $eventStore->notify($newEventsStream); //now event bus will notify projections as well

• More examples: You can see whole working example setup in IntegrationWithExampleDomainTest

Development and tests

To develop this lib we are using docker and docker-compose. After installation of those you should run:

    docker-compose up
    docker-compose run eventstore bash

Then on docker console run:

composer install
php bin/phpspec run -fpretty
php bin/phpunit