Domain-Driven Design for Microservices Architecture

Vũ Nhật Minh / @dtvd88

Agenda

• About me

• Domain-Driven Design

• DDD approach for Microservices architecture

• +α

Domain-Driven Design

• About me

• Domain-Driven Design

• DDD approach for Microservices architecture

• +α

Software development is hard

The hard part come from real-world problems

Real-world problem belongs to a specific domain

The Ubiquitous Language

Building the ubiquitous language

• Commit to use the language in everywhere

  • All communication form: speech, writing, diagrams ...

  • In the code later

• Communicate with domain experts and find keywords​

• Developers can think about keyword as classes in OOP

The model

Architecture

and design patterns

Think DDD

Layered Architecture

DDD Desgin Patterns

• Extract from the ubiquitous language
  • Entities
  • Value Objects
  • Services
• Ownership and boundaries
  • Aggregates
• Storage
  • Repositories

Entities

Find out what is Entities

Value Objects

Find out what is not need to be Entities

// Entities with same id is considered the same.
class User(val userId: Int, val name: String, val profile: SocialProfile) {
  def equals(other: User): Boolean = {
    userId == other.userId
  }
}

// Value Objects with same value is considered the same.
class SocialProfile(val facebookURL: String,
                    val twitterURL: String,
                    val githubURL: String) {
  def equals(other: SocialProfile): Boolean = {
    facebookURL == other.facebookURL &&
    twitterURL == other.twitterURL &&
    githubURL == other.twitterURL
  }
}

Services

Language's nouns can be Entities or Value Objects

class Saiyan(val name: String, val age: Int)

// Service provide a method to perform an operation
def fusionDance(left: Saiyan, right: Saiyan): Saiyan = {
  new Saiyan(left.name + right.name, math.min(left.age,right.age))
}

DDD Desgin Patterns

• Extract from the ubiquitous language
  • Entities
  • Value Objects
  • Services
• Ownership and boundaries
  • Aggregates
• Storage
  • Repositories

Chaotic Objects associations

Aggregates

Aggregates

Groups of associated objects regard to transactions

Repositories

Repository commonly refers to a storage location, often for safety or preservation.

                                                                                   Wikipedia

findPost(cond)

posts list

findPost(cond)

posts list

Entity or Value Object ?

DDD with Microservices

• About me

• Domain Driven Design

• DDD approach for Microservices architecture

• +α

There is a very, very bad nightmare for every developer

Monolithic is hell

DDD and Microservices are here to help us escape from the hell !

Microservices introduce boundaries

DDD make bounded context

DDD for multiple context

• There are advanced topics

  • Bounded Context

  • Context Map

  • Shared Kernel

  • Anticorruption Layer

  • Separate Ways

  • Open Host Service

• Read Eric Evan's book and the online sumary version ... 

Software Engineer life in Japan

• About me

• Domain Driven Design

• DDD approach for Microservices architecture

• +α

Realize two worlds

Don't fail into traps

Use your time wisely

Invest to yourself

Build awesome things

Thanks for listening