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Goat domain driven design tools

Provides a set of tooling for domain driven design. Automatic integration to Symfony >= 4 is provided via makinacorpus/goat-bundle package.

Status

This was kind of micro-framework, including many features:

• Command bus logic with a command dispatcher and a command handler locator.
• Independent message broker implementation using PostgreSQL.
• A command for reading the message broker queue and send it into the command bus synchronous dispatcher.
• A name normalization and mapping API (e.g. \App\Foo\Bar to App.Foo.Bar) for sharing business identifier across techonology boundary.
• Some rather generic, stable and functionnal event store implementation with a PostgreSQL driver.
• An event projector API for consuming event store events and projecting them into custom implementation, for populating read model databases.
• A legary repository pattern implementation.
• Preferences API restitued as pseudo Symfony environement variables.
• A Symfony bundle to tie everything.

All together this represents a huge functionnal surface, and many items in this list don't belong together.

The name goat itself refers to something stupid or insecure.

This project has lived throught 4 production projects, and still exist and is maintained, but not for long.

Next version major, i.e. 5.x will be the last one, it reprensents the current state where:

• Preferences API no long exists, and has been moved to an independant package makinacorpus/preferences-bundle (you may look it up on packagist).
• Repository pattern implementation has gone away, it was really in use in a single project, and will remain minimally maintained (bugfixes only) in an independent package as well makinacorpus/goat-domain.
• Name normalization feature as been moved to the makinacorpus/normalization package.
• New makinacorpus/message package now contains the shared message envelope and associated interfaces.
• New makinacorpus/event-store package now contains the event store and the projector API. Please note that the project API itself might end up being deprecated if we don't have any new use case.
• Lots of other dead code pieces will be trashed away.
• It will mostly remain only the command bus, dispatcher, message broker, event store and normalization API.

This will enter a state of bugfixes only, for our production projects still using it, but most of its code will progressively be deprecated in favor of new independant and more accurate packages:

• Existing makinacorpus/corebus package which is more or less the same as the dispatcher of this package, using more modern code and that is more extensively tested will eventually inherit from this dispatcher and message broker code.

Pre-requisites

Due to SQL RETURNING clause usage, this cannot work with MySQL. This feature is not SQL standard, but all of PostgreSQL, SQL Server and Oracle have a variant of this feature, therefore could work with this package.

As of now, only PostgreSQL is an active target and have been tested with.

Features

• build a domain event driven model, derived from DDD and CQS with a message broken in the middle,
• provide an event store to save everything, and replay it.

Installation

Usage

Please document me.

Dispatcher

The Dispatcher is a component that behaves like symfony/messenger component, it is the user facing interface for sending and consuming messages from a bus.

It gives two methods:

• an asynchronous message dispatch(), whose goal is to send messages to a message broker,

• a synchronous message process() whose goal is to consume messages and dispatch them to the correct message handler.

Base implementation comes down to:

• dispatch() just passes messages to a message broker,
• process() just fetch a handler using an handler locator and executes it.

All other advanced features, including event store support are implemented using dispatcher interface decorators.

A console consumer command exists, it simply fetches messages from the message broker and call dispatcher's dispatch() method.

Event store

Introduction

The EventStore is a very primitive implementation of what you might use for implementing event sourcing. It saves all events that have been throught the applications into an ordered and immutable append-only log.

Every event that have been executed in the application will be saved into this journalisation mecanism.

It works the following way:

• when a domain event is run through the dispatcher and processed synchronously the event is saved directly into the log, with the fail or success status along (a fail event is one that have been rollbacked),

• when the messenger consumes an external or asynchronous message, it goes througth the dispatcher once again, and gets saved the way it has been written above.

Its usage is optional.

Some concepts

The event store allows to partially implement an event sourcing based system or it can be used a pure journalisation mecanism without being source of the actual data.

In both case, it will be plugged onto the message bus, and store every message or domain event that happen to the system. For this to work gracefully, your own events should implement the Goat\Dispatcher\Message\Message interface in order for the event store to be able to identify every aggregate or entity that gets created or update within the system and keep track of objects life time.

It doesn't matter if you actually identify creation or modification, only a UUID is necessary, if it doesn't exist in the index, a new event stream will be created, if it exist a single event will append to the existing stream.

Advanced configuration

Please document me.

Monolog integration

Provide some extra options for monolog.

Please see the README.monolog.md file for more information.

Testing

A docker environement with various containers for various PHP versions is present in the sys/ folder. For tests to work in all PHP versions, you need to run composer update --prefer-lowest otherwise PHP 7.4 tests will fail.