Turn your startup in a stayup with DDD

A real story about DDD, startups, agility, TDD, debt (both technical and financial), culture, failure and success.

Transcript

1. Marijn Huizendveld
2. Turn your startup in a stayup with DDD
4. What to expect?
5. Real story
6. Real domain
7. Interrupt me
8. Tickets verkoop je met Pink Tie
9. Why DDD?
10. Domain Vision Statement?
11. What were we doing?
12. – Pink Tie V.O.F. “The domain model will represent available Admissions to Events that are organized by Promoters. (…)”
13. – Pink Tie V.O.F. “(…) Once an Admission has been acquired a Ticket will be issued, granting the TicketHolder access to the Event for the acquired Admission.”
14. What are we doing?!
15. DDD everywhere
16. final class GeneralTermsAndConditionsAgreementAccepted extends DomainEvent { private $agreementId; private $customerRegistrationId; private $signee; private $organization; ! public function __construct( Uuid $agreementId, $playhead, Uuid $customerRegistrationId, $signee, $organization ) { parent::__construct($playhead); ! $this->agreementId = $agreementId; $this->customerRegistrationId = $customerRegistrationId; $this->signee = $signee; $this->organization = $organization; } }
17. Wrong language in a bounded context
19. Incorrect boundaries
20. public function handle(StartPurchaseOrderIdealPayment $command) { $purchaseOrder = $this->purchaseOrders->find($command->getPurchaseOrderId()); $idealMerchant = $this->idealMerchants->find($command->getIdealMerchantId()); $idealIssuer = $this->idealIssuers->find($command->getIdealIssuerId()); ! $idealTransaction = $purchaseOrder->startIdealTransaction( $command->getIdealTransactionId(), $idealMerchant, $this->idealAcquirerConnection, $idealIssuer, $command->getReturnUrl(), $command->getRandomCode(), $command->getIdealTransactionFee() ); ! $purchaseOrder->startPaymentProcess($idealTransaction); ! // persistence order is important $this->purchaseOrders->add($purchaseOrder); $this->idealTransactions->add($idealTransaction); }
21. False domain vision
22. – Pink Tie V.O.F. “The domain model will represent available Admissions to Events that are organized by Promoters. (…)”
23. – Pink Tie V.O.F. “(…) The domain model will represent available Admissions to Events that are organized by Promoters. These Admissions can be acquired given a PricingPolicy. (…)”
24. – Pink Tie V.O.F. “(…) Once a Admission has been required a Ticket will be issued, granting the TicketHolder access to the Event for the acquired Admission.”
25. No agility
27. You apply all the patterns but it isn't working
29. Knowledge crunching the DDD startup environment
30. DDD in startups Cost Specific knowledge Difficult to hire Difficult to train Code ceremony Skilled developers Tests can slow down Knowledge crunching Initial slowdown Access to experts Perfection Slow pace of change Stiffness Lack of feedback DDD fixation Wrong abstractions Cultural issues Traps DDD all the things Lack of context Over design Unfocused effort No refinement Missing abstractions Mismatch with ubiquitous language Mismatch between model and implementation Technical debt in domain model Inertia Expensive to pay back Knowledge leaks Domain model becomes anemic Difficult to refactor High risk of issues Coupling to infrastructure Difficult to move to other infrastructure Reduces testability Incorrect boundaries Aggregates Bounded contexts Modules No domain experts Lack of feedback Self fulfilling prophecy Slow Incorrect intent Cripples communication False suggestions Leads away from real problems Frameworkization Wrong level of abstractions Wrong audience Coupling False vision/wrong perspective Leads away from the real problems Difficult to identify Even more difficult to correct Waterfall Slow time to market No feedback cycle Change of course is tough Wide vision Everything is core No time to become excellent Unskilled team Difficult to solve in the short term Expensive in the long term Many new techniques at once Lack of focus on domain Lack of refinent High risk low reward Knowledge silos Team members Areas of the code Integrations under the radar Benefit Ubiquitous language Understanding of the domain Intent Commands Analytics Evolving Testing Support Debugging Domain events Extensibility Scaling Evolving Testing Analytics Support Debugging Abstractions Emergent design Opportunities Pivot Maintainable Simplicity Agility Ease of use Adoption Little support Eases communications Domain experts Simplifies marketing effort Team members Behavior driven tests Agility Flat learning curve Visualization Bounded context Scope Isolation Low risk Decoupled Focus Specialization Fun & excitement Tools Process Knowledge crunching Explore boundaries Experiment Narratives Diagrams Visualization techniques Going backwards Visual tests Ubiquitous language Read vs. write UX state charts Boxes & arrows Estimating ROI Cost/benefit Pomodorros Planning Event storming Modeling whirlpool Agile Infrastructure Clouds Messaging CI Monitoring Code TDD Tactical patterns Natural language Ubiquitous language Temporal evolution Modularity API design Existing patterns Event sourcing CQRS Hacks Follow the current
31. Cost
33. DDD is not free of charge
34. Traps
36. You may be aware of the traps and still get caught up in them
37. Tools
39. Use the tools to solve your problem
40. Benefit
42. There is so much benefit in DDD if you get it right
43. Examples
44. Ease communication with BDD tests
45. /** * @test * @dataProvider ProvidePreSaleIdEventDetailsAndAnotherEventName::that_are_valid */ public function corrects_name_of_event( Uuid $aPreSaleId, EventDetails $someEventDetails, $anotherEventName ) { $this->scenarioToTest() ! ->given( GeneralAdmissionPrepared::withPreSaleId($aPreSaleId) ->withEventDetails($someEventDetails) ->withCapacity(1) ) ! ->when(CorrectNameOfEvent::v1($aPreSaleId, $anotherEventName)) ! ->then(NameOfEventWasCorrected::v1($aPreSaleId, 1, $anotherEventName)); }
46. Tell the story of your customer
47. Feature: Register account In order to become a customer As a promoter I want to register for an account. ! Scenario: Successful registration ! Scenario: Customer is already registered ! Scenario: Forgot to accept the General Terms and Conditions ! Scenario: Forgot to enter name ! Scenario: Forgot to enter password ! Scenario: Forgot to enter organization
48. Natural language
49. final class PleaseReserveTickets extends CommandOrderProcess { ! private $orderProcess, $reservationNumber, $tickets, $channel; ! public function __construct ( $orderProcess, $reservationNumber, $tickets, $channel ) { $this->orderProcess = (string) $orderProcess; $this->reservationNumber = (string) $reservationNumber; $this->tickets = (string) $tickets; $this->channel = (string) $channel; } }
50. final class SorryInvalidOrderPolicy extends DomainException { ! public function __construct ($aMessage) { parent::__construct($aMessage); } ! static function becauseMinOrderQuantityExceedsMaxOrderQuantity () { return new SorryInvalidOrderPolicy( 'Sorry, the minimum order quantity should be less than or ' 'equal to the maximum order quantity.' ); } }
51. final class ProvideOrderNumberInput extends PHPUnit_Framework_DataProvider { ! static public function that_is_semantically_correct () { return [ 'First order number for firsthand tickets' => [ 'aNumber' => 'A000001' ] ]; } }
52. Don’t get caught up in the patterns
53. Get caught up in your domain
54. Questions?
55. @marijn @huizendveld Thank you