Good ORMs do not call __construct a.k.a. where to fire my Domain Events

tl;dr: Entity constructor should be called once in its entire life. That’s why good ORMs don’t use constructor to reconstitute objects from the database. Good ORMs use reflection, deserialization or proxies. So, fire your Domain Events in the constructor.

Last week, I saw a presentation about going from coupled-to-framework code to a Domain-Driven Design approach in a sample application. It was a good talk. However, in my honest opinion, there were some mistakes that are important to address. In order not to troll, I have checked with the speakers to write this post ;).

One of the mistakes, that I would like to point is where a Domain Event about “a new product was created” should be trigger specifically inside the Product Entity.

Speakers were showing a “Video” Entity with a named constructor called “create”. They were calling new inside the named constructor and then firing the event. I mean, the Domain Event was not fired inside of the real constructor. Let’s see the code we’re talking about (the whole repository can be found here): Continue reading

“Domain-Driven Design in PHP” (@dddbook) is finished

Today, Keyvan, Christian and me are very happy to announce that “Domain-Driven Design in PHP” book is 100% complete. 380 pages and around 1400 readers so far.

Thanks

Thanks, thanks, thanks.

Thanks to everyone that has supported us in this project.

Thanks to Christian and Keyvan. We don’t need words to understand each other.

Thanks to our families and friends. Love is what you need to keep pushing.

Thanks to Edd Mann for helping at the beginning with the language implementation details ;).

Thanks to Matthias Noback for his suggestions and his foreword.

Thanks to Vaughn Vernon for being pragmatic and inspiring.

Thanks to Ricard Clau, Albert Casademont, Victor Guardiola and Jordi Abad for your contributions.

Thanks to Natalye Childress for non stopping asking about uppercase or lowercase. With your work, the book can be read.

Thanks to everyone that committed fixes, you are great: Jonathan Wondrusch, César Rodríguez, Yannick Voyer, Oriol González, Henry Snoek, Tom Jowitt, Sascha Schimke, Sven Herrmann, Daniel Abad, Luis Rovirosa, Luis Cordova, Raúl Ramos, Juan Maturana, Nil Portugués, Nikolay Zujev, Fernando Pradas, Raúl Araya, Neal Brooks, Hubert Béague, Aleksander Rekść, Sebastian Machuca, Nicolas Oelgart, and Marc Aube.

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Event Sourcing is not a messaging integration pattern

tl;dr: If you are sending messages to RabbitMQ to communicate one application to another, you are not doing Event Sourcing. You’re just doing messaging ;)

In the last two months, I’ve seen different nice talks using DDD, CQRS or Event Sourcing in the talk title. However, after watching the content, I think there are some general misunderstandings about some of the concepts. The most important one, in my honest opinion, is calling Event Sourcing to sending messaging to other applications using a broker. Event Sourcing is not about that. Let me explain a bit more.

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Rendimiento con Domain Events, Proyecciones y principios de CQRS

Cuando desarrollamos una aplicación nueva, todo va muy rapidito. Hay poco tráfico, pocas queries y si hay alguna más “dura” usamos alguna cache como Memcached o Redis. Pero a medida que agregamos más funcionalidad a una página, el número de queries a base de datos u otras infraestructuras va creciendo. Hasta que sin saber cómo, haces 300 queries, y no es broma, en la ficha de algún producto.

El problema es que estamos acostumbrados a hacer muchas queries de lectura y muy pocas de escritura en estructuras bastante normalizadas. Eso escala mal en base a nueva funcionalidad. Un buen approach en busca del máximo rendimiento es la consistencia eventual, estructuras desnormalizadas y proyecciones.

Os dejo el video de la formación de @AtrapaloEng sobre cómo el uso de Eventos de Dominio y el uso de conceptos de CQRS nos pueden ayudar enormemente a mejorar el rendimiento de nuestras aplicaciones.

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Domain-Driven Design: Logging with Domain Events Webcast at @AtrapaloEng (Spanish)

Cuando trabajamos con aplicaciones DDD-style (aunque para las otras también aplica), una de las preguntas clásicas es como ejecutar tareas relacionadas con infraestructura desde las zonas más internas como Value Object o Entidades, sin violar la dependencias hacia capas superiores e incluso el SRP. Un ejemplo es logar información como acciones de usuario (tipo intento de acceso al sistema, alta de usuario, baja de usuario, etc.). El pasado Viernes, orientamos la formación de @AtrapaloEng sobre este tema. Os dejo el video y los ejercicios. Formación práctica basada en el proyecto de LastWishes con múltiples ejercicios resueltos in live coding.

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