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https://github.com/tpierrain/cqrs

A simple project to explain CQRS during a live coding session at MS experiences'16
https://github.com/tpierrain/cqrs

Last synced: about 5 hours ago
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A simple project to explain CQRS during a live coding session at MS experiences'16

Host: GitHub
URL: https://github.com/tpierrain/cqrs
Owner: tpierrain
Created: 2016-09-24T21:17:04.000Z (about 8 years ago)
Default Branch: master
Last Pushed: 2017-01-09T16:45:00.000Z (almost 8 years ago)
Last Synced: 2024-06-27T13:37:42.321Z (5 months ago)
Language: C#
Homepage:
Size: 4.17 MB
Stars: 143
Watchers: 15
Forks: 32
Open Issues: 7
Metadata Files:
- Readme: README.md

Awesome Lists containing this project

README

![BookARoom](https://github.com/tpierrain/cqrs/blob/master/images/bookARoom.gif?raw=true)

BookARoom is a simple project __to explain CQRS__ during a live coding session at MS experiences'16 (__slides are available here: [https://github.com/tpierrain/CQRS-slides](https://github.com/tpierrain/CQRS-slides)__) or __[here on slideshare](http://www.slideshare.net/ThomasPierrain/cqrs-without-event-sourcing)__

The project is a __dotnet core__ ASP.NET web site (in order to be containerized in the next session), allowing users:

1. To consult and search for available rooms (READ model)
2. To book a room (WRITE model)

Of course, booking a room (write model) will impact the read model accordingly.

---
![disclaimer](https://github.com/tpierrain/cqrs/blob/master/images/disclaimer.gif?raw=true)

This project is not a real one nor a prod-ready code. The intent here is __to illustrate the CQRS pattern during a 40 minutes session__. Thus, some __trade-offs have been taken__ in that direction (e.g. the usage of *Command* and *Queries* terminology instead of domain specific names that I would have used otherwise).

##### CQRS without Event Sourcing?!?
Yes, since the timing will be short for __[this *MS experiences'16* session in Paris](https://experiences.microsoft.fr/Event/speaker/thomas-pierrain/e11c8e2e-f572-e611-80c3-000d3a2229a6)__ (no more than 30 minutes of live-coding), I've decided to focus only on CQRS pattern, WITHOUT Event Sourcing (ES). Indeed, ES is often a mental dam for people's understanding.
I also find important that people understand that __CQRS ![loves](https://github.com/tpierrain/cqrs/blob/master/images/heart.png?raw=true) Event sourcing__, but __CQRS != Event sourcing__.

---

### Highlights of the talk

1. __CQRS (WITHOUT Event Sourcing)__:
- Why CQRS?
- Pattern origin
- How read and write models articulate
- Eventual consistency challenges and options
- Short clarification between __CQRS & Event sourcing__

1. How __Outside-in TDD__ works
1. How __Hexagonal Architecture__ can help us to focus on __Domain first__, before tackling the infra code (ASP.NET) in a second time
1. What is __dotnet core__ and how it articulates with the new version of ASP.NET

---

### Projects & Dependencies
- ![directory](https://github.com/tpierrain/cqrs/blob/master/images/directory.png?raw=true) __BookARoom.Domain__: containing all the domain logic of the solution (for both read and write models). __(has no dependency)__

- ![directory](https://github.com/tpierrain/cqrs/blob/master/images/directory.png?raw=true) __BookARoom.Infra__: containing the reusable infrastructure code (i.e. non-domain one like adapters, command handler, repositories) for both read and write models. __(depends on both Domain and IntegrationModel projects)__

- ![directory](https://github.com/tpierrain/cqrs/blob/master/images/directory.png?raw=true) __BookARoom.Infra.Web__: ASP.NET core project hosting the web infrastructure code (like ViewModels, Views and Controllers) which relies on the BookARoom.Infra code. __(depends on both Domain, Infra and IntegrationModel projects)__

- ![directory](https://github.com/tpierrain/cqrs/blob/master/images/directory.png?raw=true) __BookARoom.Tests__: containing tests for all projects. __(depends on all the other BookARoom projects)__

- ![directory](https://github.com/tpierrain/cqrs/blob/master/images/directory.png?raw=true) __BookARoom.IntegrationModel__: command-line project to generate integration json files for hotel (from code). __(has no dependency)__

---

### Tips and tricks

##### How to run the tests

Note: resharper and ncrunch don't support yet dotnet core; you can only run them via Visual Studio test runner (e.g. Ctrl-R, A) or by executing:

dotnet test

within the BookARoom.Tests project directory.

---

### CQRS in a nutshell

There are many forms of CQRS implementation. The implementation of the BookARoom project follows this version:

![directory](https://github.com/tpierrain/cqrs/blob/master/images/CQRSdiagram.png?raw=true)

from original source: [https://msdn.microsoft.com/en-us/library/jj591573.aspx](https://msdn.microsoft.com/en-us/library/jj591573.aspx)

---
![lab](https://github.com/tpierrain/cqrs/blob/master/images/Lab.jpg?raw=true)

The objective of this lab is to __add the "cancel a reservation" feature__.

__[Step by step Instructions (following outside-in TDD technique) are presented here](LabInstructions.md)__.

---

### Tracks of improvement

1. Fight against the current anemic model (mainly because I never worked on that topic and that I don't have any expert available to help me ;-( and embrace more the ubiquitous language of this domain.

...