my story

• coupled code
• reusability via services
• inject dependencies
• modelling DB not business problem
• thinking about DB more than problem

RegistrationController

• validate data
• create user object
• persist user object
• create activation email
• send email
• save user to elasticsearch

RegistrationController

RegistrationService

ORM

RegistrationEmailManager

Mailer

EmailComposer

ORM

ElasticSearchManager

UserImportManager

UserCsvProcessor

UserValidationService

UserImportFetcher

ShoppingService

OrderService

UserManager

Product

Category

• id
• title
• description
• categoryId
• price
• vendorId
• createdAt

• id
• title
• parentId
• createdAt

Product

Category

• id
• title
• description
• categoryId
• category_level_0
• category_level_1
• category_level_2
• price
• vendorId
• createdAt

• id
• title
• parentId
• category_level_0
• category_level_1
• category_level_2
• createdAt

Product should be visible in all parent categories

Show products on site

class ProductsRepository
{

    public function getProducts($categoryId,$categoryLevel,...){
        ...
        $this->addWhere('category_level_'.$categoryLevel,$categoryId);
        ...
    }
}

Edit category: change parent

• calculate new category levels
• find all products in that category
  • update each category level

Pretty fine on 100 products

Timeout on 10.000 products

Product

Category

• id
• title
• description
• categoryId
• category_level_0
• category_level_1
• category_level_2
• discount
• price
• vendorId
• createdAt

• id
• title
• parentId
• category_level_0
• category_level_1
• category_level_2
• createdAt

We are opening special category with discounts

Show product on site

class ProductsRepository
{

    public function getProducts($categoryId,$categoryLevel,...){
        ...

        if( $categoryId === '34242'){
            $this->addWhere('discount is not null');
        }else{
            $this->addWhere('category_level_'.$categoryLevel,$categoryId);
        }
        ...
    }
}

Get product price

class Product
{

    public function getPrice(){
        ...

        if( !is_null($this->discount)){
            $price = $this->price;
            $price *= (100 - $this->discount)/100;
            return $price;

        }
        return $this->price;
    }
}

Miro Svrtan

senior developer 

@msvrtan

as web is growing

more and more core business systems are web

simple CMS

simple webshops

existing practices and pattern

existing practices and pattern

new ideas

eventsourcing

command query responsibility segregation

Domain

class RegisterController
{
    public function registerUser($form){
       $....
       $this->validate(...);
       $....
       $this->fillUpUserObject(...);
       $....
       $this->save(...);
       $....
       $this->sendConfirmationEmail(...);
       $this->saveUserInTextSearchEngine(...);
       $....
       $this->showView(...);
    }
}

class RegisterController
{
    public function registerUser($form){
       $....
    }
    public function registerUserApi($apiData){
       $....
    }
}

class CsvImportController
{
    public function importUsersCsv(){
       $data = $this->readFromDisk('somefile.csv');
       $....
    }
}


class RemoteImportController
{
    public function importFromRemoteSystem(){
       $data = curl(..);
       $....
    }
}

UserRegisteredEvent

SendActivationEmail

SaveInTextSearchEngine

class UserRegisteredEvent
{
    private $userId;

    public function __constuctor($userId)
    {
        $this->userId=$userId;
    }

    public function getUserId()
    {
       return $this->userId;
    }
}

class SendActivationEmail
{
    ... 

    public function doWork(UserRegisteredEvent $event){
       $....
    }

    ...
}

class SaveUserInTextSearchEngine
{
    ...

    public function doWork(UserRegisteredEvent $event){
       $....
    }

    ...
}

How do we connect event to subcriber?

class MessageBus{

    private $list=[];

    public function add(string $eventName, array $subscriberNames)
    {
        $this->list[$eventName] = $subscriberNames;
    }

    public function doWork($event)
    {
        foreach($this->findSubscribers($command::class) as $subscriber)
        {
             $subscriber->doWork($event);
        }
    }
}

class RegisterController
{
    public function registerUser($form){
       $....
       $this->validate(...);
       $....
       $this->fillUpUserObject(...);
       $....
       $this->save(...);
       $....
       $messagebus->doWork(new UserRegisteredEvent($userId));
       $this->showView(...);
    }

    public function registerApiUser($json){
       $....
       $messagebus->doWork(new UserRegisteredEvent($userId));
       $this->showView(...);
    }
}

Changes

• MessageBus
• UserRegisteredEvent
• SendActivationEmail
• SaveInTextSearchEngine

How hard is it to modify now?

Switch email provider

• MessageBus
• UserRegisteredEvent
• SendActivationEmail
• SaveInTextSearchEngine

change this class

Change text search engine

• MessageBus
• UserRegisteredEvent
• SendActivationEmail
• SaveInTextSearchEngine

change this class

Stop sending activation emails

• MessageBus
• UserRegisteredEvent
• SendActivationEmail
• SaveInTextSearchEngine

delete this class

Registration

is still duplicated...

RegisterUserCommand

RegisterUserHandler

class RegisterUserCommand
{
    private $userId;
    private $username;
    private $email;

    public function __constuctor($userId,$username,$email)
    {
        $this->userId    = $userId;
        $this->username = $username;
        $this->email    = $email;
    }

    public function getUserId()
    {
       return $this->userId;
    }

    public function getUsername()
    {
       return $this->username;
    }

    public function getEmail()
    {
       return $this->email;
    }
}

class RegisterUserHandler
{
    ...

    public function handle(RegisterUserCommand $command)
    {
        $...
        $...
        $...
        $messagebus->doWork(new UserRegisteredEvent($userId));
    }

}

class RegisterController
{
    public function registerUser($form){
       $....
       $this->validate(...);
       $....
       $commandbus->handle(new RegisterUserCommand(...));
       $this->showView(...);
    }

    public function registerApiUser($json){
       $....
       $commandbus->handle(new RegisterUserCommand(...));
       $this->showView(...);
    }
}

CHE

command handler event

command pattern

event pattern

RegisterUserCommand

RegisterUserHandler

UserRegisteredEvent

SendActivationEmail

SaveToTextSearchEngine

RegistrationController

ImportController

CLI

AdminController

Commands

• action to take
  • RegisterUser
  • SendEmail
  • BuyMilk
• command bus
• 1 command
  • exactly 1 handler

Events

• what happened
  • UserRegistered
  • EmailSent
  • MilkBought
• event bus
• 1 event 
  • 0,1,2,3,... subscribers

User still waits for email to be sent :(

• create SendActivationEmailCommand & Handler
• make SendActivationEmailSubscriber launch command instead of doing work
• add queueable command bus
• send command to queuable command bus
• worker(s) will do rest of the job
• eventual consistency issues!

Issue tracker: Issue

How long is this urgent bug opened?

No one is assigned to it?

Lets check the logs

• IssueOpened: 123456789 [2016-06-11 22:22:11]
• IssueClosed: 123456789 [2016-06-12 12:00:11]
• IssueReopened: 123456789, [2017-01-04 11:01:11]

• We are missing details now :(
• Lets add logging when priority changes
• 2months later: lets add logging when user is assigned/removed

New company policy: log everything

We just lost valuable data :(

Logging stuff

class EventBus extends MessageBus
{

    public function doWork($event)
    {
        parent::doWork($event);
        $this->saveSomewhere($event);
    }
}

class UpdateIssueHandler
{
    public function handle(UpdateIssue $command){
       $....
       $logger->info('Title on issue $id change to ' . $title);
    }
}

class UpdateIssueHandler
{
    public function handle(UpdateIssue $command){
       $....
       $eventbus->doWork(new IssueTitleChanged($id,$title));
    }
}

I'm too lazy to add Event here

What if instead of logging, we create object state from events?

IssueCreated(123, 'Something', 'text', BUG, NORMAL, '2016..')

IssueAssigned(123, TeamManager, '2016-06-12 10:00:00')

PriorityChanged(123,URGENT, '2016-08-11 15:46:33')

IssueDellocated(123,'2016...')

IssueClosed(123,'2016...')

IssueReopened(123, '2017-03-16 11:01:35')

TitleChanged(123, 'Register button doesnt work in IE', '2016...')

Issue object is now in same state as in CRUD

Event sourcing

class Issue
{
    private $id;
    private $title;
    private $text;
    private $assigned;
    private $type;
    private $status;
    private $priority;

    public function changePriority($newPriority){
        $this->priority = $newPriority;
    }

}

CRUD

class Issue
{
    ...

    public function changePriority($newPriority){
        if($newPriority !== $this->priority){
            $this->record(new PriorityChanged($this->id,$newPriority);
        }
    }
}

Eventsourcing #1

class Issue
{
    ...

    private $newEvents=[];


    public function changePriority($newPriority){
        if($newPriority !== $this->priority){
            $this->record(new PriorityChanged($this->id,$newPriority);
        }
    }

    private function record($event){
        $this->apply($event);
        $this->newEvents[] = $event;
    }

    public function apply($event){
        $className = get_class_name($event);
        $methodName = apply.$className;
        if( method_exists($this,$methodName){
             $this->$methodName($event);
        }
    }
}

Eventsourcing #2

class Issue
{
    ...

    private $newEvents=[];


    public function changePriority($newPriority){
        if($newPriority !== $this->priority){
            $this->record(new PriorityChanged($this->id,$newPriority);
        }
    }

    private function record($event){
        $this->apply($event);
        $this->newEvents[] = $event;
    }

    public function apply($event){
        $className = get_class_name($event);
        $methodName = apply.$className;
        if( method_exists($this,$methodName){
             $this->$methodName($event);
        }
    }

    public function applyPriorityChanged(PriorityChanged $event){
        $this->priority = $event->getPriority();
    }

}

Eventsourcing #3

class Issue
{
    ...

    private $newEvents=[];


    public function changePriority($newPriority)
    {
        if($newPriority !== $this->priority){
            $this->record(new PriorityChanged($this->id,$newPriority);
        }
    }

    private function record($event)
    {
        $this->apply($event);
        $this->newEvents[] = $event;
    }

    public function apply($event)
    {
        if( get_class_name($event) === PriorityChanged::class){
             $this->priority = $event->getPriority();
        }
        ..
    }
}

Eventsourcing #4

$issue = new Issue();

$data = $db->get('SELECT * FROM issue WHERE id = 123');

foreach($data as $property => $value){
    $propertySetterName = set.$property;
    $issue->$propertySetterName($value);
}

Load Issue object: CRUD

$issue->changePriority('URGENT');

$db->update('UPDATE ...);

Save Issue object: CRUD

IssueCreated(123, 'Something', 'text', BUG, NORMAL, '2016..')

IssueAssigned(123, TeamManager, '2016-06-12 10:00:00')

PriorityChanged(123,URGENT, '2016-08-11 15:46:33')

IssueDellocated(123,'2016...')

IssueClosed(123,'2016...')

IssueReopened(123, '2017-03-16 11:01:35')

TitleChanged(123, 'Register button doesnt work in IE', '2016...')

Event store table

$issue = new Issue();

$data = $db->get('SELECT * FROM event_store where object_id=123 and class_name=issue');

foreach($data as $item){
    $event = deserialize($item['event']);
    $event->apply($event);
}

Load Issue object: EventSourcing

$issue->changePriority('URGENT');

foreach( $issue->getNewEvents() as $newEvent)
{
    $db->insert('INSERT INTO...');
}

Save Issue object: EventSourcing

Hm, how do we show all open issues on our homepage?

We run events for each object and check state?

Hm, how do we show all open issues on our homepage?

We run events for each object and check state?

Any experience with text search engines?

• Our blog posts are in MySQL
• We save id, title and text to elasticsearch
• When user searches our blog, we ask elasticsearch for results

We want to make our blog posts text searchable and we use elastic search for that

$blogPost = new BlogPost();
$blogPost->setTitle(..)
...

$orm->save($blogPost);

$elasticSearch->save($id,$title,$text,...);

Saving a blog post

$results = $elasticSearch
           ->searchFor('some words');

Searching blog posts for 'some words'

CQRS

Command Query Responsibility Segregation

• separate models to write/read
• customized data for our need

IssueCreated(123, 'Something', 'text', BUG, NORMAL, '2016..')

List of open issues: id and title

class OpenIssue
{
    private $id;
    private $title;

    
     public function setId($title)
     {
          $this->id=$id;
     }

     public function getId()
     {
          return $this->id;
     }

    
     public function setTitle($title)
     {
          $this->title=$title;
     }

     public function getTitle()
     {
          return $this->title;
     }
}

OpenIssue: CRUD

class IssueCreatedSubscriber
{
     public function doWork(IssueCreated $event)
     {
          $openIssue = new OpenIssue();
          $openIssue->setid($event->getId());
          $openIssue->setTitle($event->getTitle());
          $orm->save($openIssue);
     }
}

class TitleChangedSubscriber
{
     public function doWork(TitleChanged $event)
     {
          $openIssue = $orm->load($event->getId());
          $openIssue->setTitle($event->getTitle());
          $orm->save($openIssue);
     }
}

class IssueClosedSubscriber
{
     public function doWork(IssueClosed $event)
     {
          $openIssue = $orm->load($event->getId());
          $orm->delete($openIssue);
     }
}

List of open issues: id and title

OMG

Admin:Listings to verify

Listings to verify

Listings to verify

v2

ListingCreatedSubscriber

ListingRejectedSubscriber

EventSomethingHappenedSubscriber

...

v2