Aim: learn basics of event-sourcing pattern and its caveats.
This project builds on example from presentation from [Mathias Verraes - Practical Event Sourcing](http://verraes.net/2014/03/practical-event-sourcing/).
### Event Sourcing / DDD / CQRS
# Learning matherial
Bellow is learning matherial that I've used to dive into event DDD (and its implementations) deeper.
## DDD: Domain Driven Design
I've put DDD in it's own section because DDD is more analysis process then collection of structural patterns.
-[Jimmy Bogard: Domain Driven Design: The Good Parts](https://www.youtube.com/watch?v=U6CeaA-Phqo)
-[book: Eric Evans: Domain-Driven Design - Tacking Complexity in the Heart of Software](https://www.amazon.com/Domain-Driven-Design-Tackling-Complexity-Software/dp/0321125215)(book; read especially bounded context capture)
-[Eric Evans: Tackling Complexity in the Heart of Software](https://www.youtube.com/watch?v=dnUFEg68ESM)(10 years later; explains nicely how to read the book)
-[Greg Young: A Decade of DDD, CQRS, Event Sourcing](https://www.youtube.com/watch?v=LDW0QWie21s)
## Case studies
-[Lufthansa case study](https://drive.google.com/file/d/0B_enB2DMKeyzbF96VjdKdjIzOHc/view)
## Technical stuff
This sections actually describes how people are implementing their domains discoved by using DDD. **Be careful applying patters bellow blindly.**
## Event Sourcing + CQRS
Alternative implementation of domain model persistence layer which stores complete history of all events that happend to domain in past.
-[Greg Young's hi-level overview of CQRS/DDD](https://www.youtube.com/watch?v=KXqrBySgX-s)
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-[Greg Young's full and up-to-date DDD/CQRS/EventSourcing class](http://subscriptions.viddler.com/GregYoung)
-[Mathias Verraes' elaborate on domain events](http://verraes.net/2014/11/domain-events/) - *Domain Events allow you to segregate the models of different systems*
-[unknown's Domain Driven Design Through Onion *Architecture*](https://www.youtube.com/watch?v=pL9XeNjy_z4)
-[CQRS.nu](http://cqrs.nu/)
-[DDD Community](http://dddcommunity.org/)
### DDD in PHP
-*Tip:* Try to watch some microservices / stream processing videos. You will see unxpected similarities.
### (The structural part of) DDD in PHP
- William Durand: DDD with Symfony2:
-[Folder Structure And Code First](http://williamdurand.fr/2013/08/07/ddd-with-symfony2-folder-structure-and-code-first/)
-[Making Things Clear](http://williamdurand.fr/2013/08/20/ddd-with-symfony2-making-things-clear/)
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-[Jan Kuchar's second sanbox](https://gitlab.grifart.cz/jkuchar1/thesis-example-application)
-[DDDinPHP](http://dddinphp.org/)
### Message Buses / libraries
-[Prooph](http://getprooph.org/)(cool one!)
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-[EventSourcing at BlaBlaCar](http://blablatech.com/blog/micro-service-at-blablacar) + Matthieu Moquet: [CQRS & Event Sourcing](https://speakerdeck.com/mattketmo/cqrs-and-event-sourcing)
-[GitHub: example applications written with CQRS/event sourcing pattern](https://github.com/dddinphp)
## Notes / TODOs
- [ ] How to make proper relation between Product and Basket?
- [ ] How to access product name when product-related event occurs - aggregate does not expose any state?! (should I access read model from write model?)
- [ ] If aggregate produces event but it does not change state in any way, should it have empty apply() method for this event or should framework just skip this event. (this can lead into hard discoverable typo errors)
- [ ] Is there any point of adding events when loading from history into object "recoded events"?
### Notes / TODOs
## Case studies
- [x] How to make proper relation between Product and Basket?
-**Answer:** Analyse bounded contexts. (probably in most domains use two separate AggregateRoots)
- [x] How to access product name when product-related event occurs - aggregate does not expose any state?! (should I access read model from write model?)
-**Answer:** Access read side if needed or use heavy events.
- [x] If aggregate produces event but it does not change state in any way, should it have empty apply() method for this event or should framework just skip this event. (this can lead into hard discoverable typo errors)
-**Answer:** I would prefer to hot have this methods in aggregate and have some kind of static analysis check for method name and type consistency (in PHP which does not support method overloading).
- [x] Is there any point of adding events when loading from history into object "recoded events"?
-**Answer:** No, if you load them there, they will be persisted once more / there will be need for merge proccess.
-[Lufthansa case study](https://drive.google.com/file/d/0B_enB2DMKeyzbF96VjdKdjIzOHc/view)
