Racine's 1st and 2nd wok from her paintings class

 Racine's first painting class work.

She wants to be 3-years old, even she is already 5.

Racine's second painting class work. It is amazing, and Racine is the the fastest one in the class. I love the big dragonfly, a lot of her thought are draw down.

 

 

 

 

 

 

 

 

Racine's first PC mouse painting.

 

I am so proud of you, Racine!

CQRS + Event Sourcing Distribute Architecture Design

Preface

Very good I got a chance to attend the DevTeach 2012 at Vancouver. Even though I only get one day to be there, I am still so happy that we will see what other company are going in Architecture level. 

First I must say thanks to those excellent speakers to show my respect:

Rob Daigneau

Dylan Smith

Ted Neward 

Vincent Grondin

This blog is what I learned form Dylan, and the same time added some my thought to make it better in my opinion.

Content

1. What is CQRS 

It stands as Command Query Responsibility Segregation

Strong point:

The core concepts is split write and read behavior to Command Handler and Query Handler, and it is really good to increase scalability for our server.

Imagine, a cluster which have 2 writing server and 20 read server based on 10 database, we can easily make it.

Weak point:

Command/Query handler is easy to implements, but it less extensibility and flexibility for reuse existing under layer modules. For examples: we want detect a behavior if user did command A, and then B, then D, we should do some specific thing for the case.

2. Event Sourcing

We all know the best benefit for Event-driven is we have flexibility and extensibility to hook up new features into the existing software. Based on CQRS's major weakness, we know if we mix this 2 architecture style together, we will have a round result.

3. CQRS + Event Sourcing

Based on Dylan's model, I added some specific part(red circle) in bellow overall figure:

Architecture illustrate for CQRS+ES

Core classes:

CommandHandler

Queryhandler 

DomainObject

Repository

Subscriber

EventHandler

DTO

I do not have time to write a small prototype for this, but I believe it is is good to deal with a large scale system.

4 Benifits

• Simple
• E=mc^2. Everything  should be made as simple as possible, not simpler. In this architecture design, a new feature we can easily implement a bunch of classes, e.g. Command, Query, Repository...

• Single Responsibility Principle

• Scalability

1. Split write and read
2. Support sync and notification evens

• Flexibility & Extensibility
• Event Bus allow us plug in new module to handler new events

• Can be noSQL System 
• Writing to a file server, QUEUE

• Testing 
• Each class are single responsibility, we can easily write unit test with mock

.........................................
Any comments are welcome.