Domain Driven Development applied
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(println "Hello World! :)")
Transcript of Domain Driven Development applied
(println "Hello World! :)")
DDD as an implementation detail
Eloi PochSergi González
Who$are$we?$$
!es.linkedin.com/in/eloipoch/$
$
$@eloipoch$
Eloi!Poch!!Technical!Lead!at!@Akamon!• So8ware$Developer$• Clojure$developer$wannabe$• Want$to$code$in$Castefa$beach$while$drinking$wine$
(conj '(1 2 3) 4)
Who$are$we?$$
!es.linkedin.com/in/sergigp/$
$
$“SergiGP$
Sergi!!Technical!Lead!at!@Akamon!• So<ware$Developer$• Chief$Trolling$Officer$• Two$animals$remaining$to$have$an$urban$zoo$
Akamon
A little bit on Akamon before we deal with the technical stuff
We#develop#Social#Casino#Games#
Por$olio'of'Facebook'games'
Por$olio'of'Mobile'apps'
Recently(launched(a(new(Casino(Suite(
Technically …
Flash Client Game Server Backend
AS3 Nova
Java JReactive & Vertx
PHP Horus
@eloipoch @jordillonch @SergiGP
@jorgeavila_ss @jdiezc @jvalduvieco @amassa5
Who we are? The backend team
Development Problems
Our expectations…
PerformanceBig DataDifficult AlgorithmsConcurrencyReal time analyticsScalability
The ugly truth…
Technical Problems
Code ComplexityBig ball of mudShared StateCoupling
& Non-Technical problems
Different Cultures
Tackling Complex CodeThe Philosophy
Simple made Easy
Complex((
One(role(
One(task(
not(a(single(opera2on(
(
OBJECTIVE
Hard(
Familiar,(near(your(
knowledge(
(
(
Simple(vs(Easy((
SUBJECTIVEOBJECTIVE
Simple vs Easy
$mysqli = new mysqli("localhost", "horus", "olakease", “suite"); $mysqli->query("INSERT INTO users …”))
SIMPLE
EASY
/** * @ORM\Entity * @ORM\Table(name="product") */ class Product
$sum = function ($carry, $item) { return $carry + $item; } array_reduce([1, 2, 3], $sum);
$acc = 0; foreach ([1, 2, 3] as $value) {
$acc += $value; }
SIMPLE
EASY
(reduce + [1 2 3])
Simple vs EasySimple vs Easy
Simplicity vs Easiness
• Easy to understand
• Easy to debug
• Easy to change, flexibility, maintenable
• Easy to use
• Hard to debug
• Hard to change
Complected
• Something does more than one thing and you can’t split it easily
• Source of accidental complexity
• DON’T DO IT
Essential ComplexityVS
Accidental Complexity
Do not complect, compose
Tackling Complex Code
The Theory
Organisational level
Pair Programming
Pull Requests
Code Reviews
Continuous Integration
Self Empowerment
Never ask for permission unless it
would be reckless not to
Trust
Great teams are unafraid to air their dirty laundry, admit their mistakes, their weaknesses and their concerns
without fear. Patrick Lencioni
Technical Level
Lean Approach
Any model/solution is provisional
YAGNIYou Aren’t Gonna Need It
DDD Concepts
• DDD Tactical:
• Application Services
• Domain Services
• Domain Events
• Repositories
• AR & VO
• DDD Strategical:
• Modules
• Bounded Contexts
• SubDomains
• Context Maps
CQRS Concepts
Hexagonal Architecture
TDD & BDD
Tackling Complex Code
The Practice
Divide, Test & Conquer
Product Entity Example
ProductId
NameDescription
PriceCurrencyImage Url
CoinsStoreId
Product
Product Descriptions
Product Prices
Stores
Product Benefits
Product Images
ProductId
Product Description
Product Price
Stores
Product Benefit
Product Image
DescriptionName Currency
Amount
CoinsStoreId
Image Url
ProductId
Product Description
Product Price
Stores
Product Benefit
Product Image
DescriptionName Currency
Amount
CoinsStoreId
Image Url
Product BC
ProductId
Product Description
Product Price
Stores
Product Benefit
Product Image
DescriptionName Currency
Amount
CoinsStoreId
Image Url
Pricing/Sales BC
Product BC
Product
Id
BenefitId
Product Price
ProductId
Amount
Currency
Product Description
ProductId
Name
Description
Product Benefit
Id
Amount
VirtualMoneyId
Product Store
ProductId
StoreId
HORUS
Big Picture
• Directories: 773
• Files: 1501
• Lines of code: 113885
• Non-Comment Lines of Code: 88806 (80%)
• Average Class Length: 14 lines
• Average Method Length: 2 lines
• Cyclomatic Complexity / LLOC: 0.06
• Cyclomatic Complexity / Number of Methods: 1.21
HORUS
Big Picture of our Code in Horus
• Directories: 773 / 558
• Files: 1501 / 1001
• Lines of code: 113885 / 41205
• Non-Comment Lines of Code: 88806 (80%) / 38045 (92%)
• Average Class Length: 14 lines / 5 lines
• Average Method Length: 2 lines / 2 lines
• Cyclomatic Complexity / LLOC: 0.06 / 0.03
• Cyclomatic Complexity / Number of Methods: 1.21 / 1.14
UserPostController Command Bus
UserRegistratorCommandHandler
UserRegistratorDomain Event
Publisher
UserRegisteredDomainEventSubscriber
UserAccountOpener
User UserRepository Event Subscribers
.
.
.
POST /users[
userId: 0db90987-5ce1-4683-bb05-7d1b5539cb0b]
Command Handlers
.
.
.
UserR
egisteredDom
ainEvent
User
HORUS
BASIC REQUEST
UserRegistrationCommand
UserRegistrationCommand
userIdanalyticsContextId
userIdanalyticsContextId
UserRegisteredDomainEvent
userId
analyticsContextId
id (Economy Account)
UserPostController Command Bus
UserRegistratorCommandHandler
UserRegistratorDomain Event
Publisher
UserRegisteredDomainEventSubscriber
UserAccountOpener
User UserRepository Event Subscribers
.
.
.
POST /users[
userId: 0db90987-5ce1-4683-bb05-7d1b5539cb0b]
Command Handlers
.
.
.
UserR
egisteredDom
ainEvent
User
HORUS
BASIC REQUEST
UserRegistrationCommand
UserRegistrationCommand
userIdanalyticsContextId
userIdanalyticsContextId
UserRegisteredDomainEvent
userId
analyticsContextId
id (Economy Account)
UserModule
EconomyModule
Operational
Analytics
Support
Marketing
DE
C
Q
Q
We are still COUPLED !!
Operational
Analytics
Support
Marketing
HTTP
…
Tackling Complex Code
The Conclusions
Mistakes
• Do not store domain events
• Own libraries for CQRS & DDD
• Do not use Domain Services
• Domain events with wrong identifiers
• Couple App Services to Commands & Queries
• Not start earlier some Modules/Bounded Contexts
Mistakes
• Let the DB guide us
• Let the framework guide us
Problems
• Domain Events: Lost of order (async)
• Doctrine
• Unit Of Work + Integration Test = Fail
• Embedded: Identifier or not
• Behat: The Container
Tips & Tricks
• Repositories:
• Just add, save and find
• Use of DQL implies the schema is too complex
• Controllers: 50 lines of code
• Application Services: Avoid business logic
• One step at time: Hex. Arch. -> DDD -> CQRS -> ES?
• Start it as a Module and promote it later to BC
TROLLTIMEQUESTIONS?
Akamon Developers
