Application with CQRS and Event Sourcing built on Rails and Rails Event Store.

👉 ecommerce.arkademy.dev

Event storming (events and commands) - Miro documentation

Domains exist in directories starting at ecommerce.

ecommerce/
├── crm
├── inventory
├── ordering
├── payments
├── pricing
└── product_catalog
└── shipping

Each one has a README introduction:

• CRM
• Inventory
• Ordering
• Payments
• Pricing
• Product Catalog
• Shipping

Order management application lives at rails_application directory.

This application simulates a process of managing orders.

We start with a list of exiting products and customers (populated with seeds).

The customer perspective is "simulated" only - via using the select box.

• Add/remove some of the existing products to the order
• Choose the customer
• Submit the order
  • after this you can't update the order items or customer
  • it generates the order number like "2021/03/20" (the last part is random(100))
• Look at the order
• Look at the history of events (in the Rails Event Store Browser)

There's only one read model - which helps us listing all the orders and individual order details.

It consists of 2 ActiveRecord classes: Order and OrderItem.

There's a process manager responsible for dealing with the process of expiring orders.

It takes the following events as the input:

• Ordering::OrderSubmitted
• Ordering::OrderExpired
• Ordering::OrderPaid
• Payments::PaymentAuthorized
• Payments::PaymentReleased

When certain conditions are met the process manager return a ReleasePayment command.

Another process manager is responsible for confirming order. It does it, when a successful payment is detected.

This project has several high-level goals:

• to show that it's possible to modularize a non-trivial Rails app
• to serve as an example of a DDD project (not only in Rails)
• to let people play with this codebase to get a feel if DDD is for them
• to show that tests can be fast if the app is well modularized
• to show a proper pyramid of tests
• to teach event-driven architectures
• to show how to use RailsEventStore
• to bring DDD enthusiasts from .Net/Java/PHP/others to the Ruby world 😎
• to popularize professional testing techniques - mutation testing
• to allow programmers to reuse existing and popular domains
• to build new apps like Lego

We welcome all the contributors here.

As you see, this project is not an usual Rails project. Many Rails conventions are not followed here. Usually there's a good reason for that. Trust us, but feel free to challenge our decisions.

As for the local dev setup:

• we use Makefile, so make install should simplify a lot
• there's docker-compose in the rails_application, if you're into Docker

Things worth knowing about:

• Zeitwerk is not used here - you need to be explicit with requires
• Any IDE should work with this codebase
• We use mutant for mutation testing, code that is untested breaks the build.
• But sometimes we allow ourselves for mutant ignores (explicit mark for mutant to ignore)
• Mutant ignores are considered technical debt.
• REST is not followed here for routes, no need for that
• register_command accepts events because it's used in the /architecture view. It's a visualisation/documentation of the events flow
• Certain ideas are in the Work In Progress status - sorry about that
• Feel free to ask.
• After you make a contribution, we'll invite you to a special Discord
• Contributing is a good way to learn DDD/CQRS/Event sourcing.

Over time we have developed a number of DDD-related online courses. We now sell them as part of one membership access via arkademy.dev for $49/month.