Practical insight into modulithic architecture Max Beckers 𝕏 @maxbbeckers Elbphilharmonie Hamburg

Contact: 𝕏 @maxbbeckers [email protected] linkedin.com/in/maximilianbeckers Max Beckers Solutions Architect • Working for / • Living near Kiel, Germany • Symfony Experience since 2012

Software architecture is always about finding the best solution for your use case and your application in your specific context. The challenge is to find the right balance between simplicity and flexibility. 𝕏 @maxbbeckers

Simplicity in focus Monoliths 𝕏 @maxbbeckers

Focusing on flexibility Microservices 𝕏 @maxbbeckers

Finding its place between Monoliths and Microservice Modulithic Architecture Modular Monolith 𝕏 @maxbbeckers

𝕏 @maxbbeckers Monolith – Modulith – Microservice – Overview Microservices Modulith Monolith Multiple Both possible Single Codebase Multiple Single Single Releases Multiple Single Single Deployments Domain / Business centered Domain / Business centered Technical design Design Principles Orchestration & Monitoring Releases / Coordination Understanding Code Complexity Network overhead Direct calls Direct calls Performance Services + Integration Modules + Integration Whole codebase Testing

𝕏 @maxbbeckers Monolith – Modulith - Microservice Microservices Modulith Monolith ❌ ✔ ✔ Simplicity ✔ ❌* ❌ Scalability ✔ ✔ ❌ Low Coupling ✔* ✔* ❌* Maintainability ❌ ✔ ✔ Single point of failure ✔ ❌* ❌ Free in technology usage ❌ ✔ ✔ Transaction Handling

Let's dive into the example … 𝕏 @maxbbeckers

𝕏 @maxbbeckers

𝕏 @maxbbeckers

𝕏 @maxbbeckers Architecture Overview API GATE WAY Payment Processing Order Management Customer Management SEPA Mandate Payment Provider

𝕏 @maxbbeckers Symfony Application Overview Use-Case based Structure instead of technical namespaces at the first level.

𝕏 @maxbbeckers Generate Code from the API #!/usr/bin/env bash openapi-generator-cli generate \ -i ./public-contract-definition.yaml \ -g php \ -o ./generated \ --additional-properties=\ invokerPackage=Worldline\\Payments\\Api\\V2,\ modelPackage=Models,\ artifactVersion=2.279.0,\ composerPackageName=worldline/payment-api,\ licenseName=MIT

𝕏 @maxbbeckers Composer part "repositories": [ { "type": "path", "url": "api-spec/generated", "options": { "symlink": true } } ], $ composer require worldline/payment-api:@dev ./composer.json has been updated Running composer update worldline/payment-api Loading composer repositories with package information Updating dependencies

𝕏 @maxbbeckers API Gateway "Internal" namespace denotes module internal functionality – cannot be accessed outside the module context.

𝕏 @maxbbeckers Modulith internal APIs - Objects Modules have data structures defined by DTOs

𝕏 @maxbbeckers Modulith internal APIs - Services Services in a module are called using interfaces. In a Microservices context, this could be the OpenAPI Spec.

𝕏 @maxbbeckers Modulith internal APIs - Messages Modules can consume messages defined in Message. namespace App\Order\Message; use App\Order\Dto\OrderDto; class PersistOrderEvent { public function __construct( private readonly OrderDto $orderDto ) { } public function getOrderDto(): OrderDto { return $this->orderDto; } }

𝕏 @maxbbeckers Modulith internal APIs - Overview • DTOs – Data Structure for the API of the Module • Interfaces – Endpoints for the API of the Module • Messages – Async Communication API of the Module • Exceptions – Error Responses of the Module

𝕏 @maxbbeckers #[Route(name: "app_v2_payments_")] class PaymentsController extends AbstractController { public function __construct( private readonly PaymentServiceInterface $paymentService, private readonly PaymentMapper $paymentMapper ) {} #[Route('/v2/{merchantId}/payments', name: 'create_payment', methods: ['POST'])] public function create(Request $request, string $merchantId): JsonResponse { /** @var CreatePaymentRequest $createPaymentRequest */ $createPaymentRequest = ObjectSerializer::deserialize($request->getContent(), CreatePaymentRequest::class); $paymentRequest = $this->paymentMapper->mapCreatePaymentRequestToPaymentDTO($createPaymentRequest, $merchantId); $paymentResponse = $this->paymentService->pay($paymentRequest); $response = $this->paymentMapper->mapPaymentDTOToPaymentResponse($paymentResponse); return $this->json(ObjectSerializer::sanitizeForSerialization($response), 201); } } Payments Controller

𝕏 @maxbbeckers #[Route(name: "app_v2_payments_")] class PaymentsController extends AbstractController { public function __construct( private readonly PaymentServiceInterface $paymentService, private readonly PaymentMapper $paymentMapper ) {} #[Route('/v2/{merchantId}/payments', name: 'create_payment', methods: ['POST'])] public function create(Request $request, string $merchantId): JsonResponse { /** @var CreatePaymentRequest $createPaymentRequest */ $createPaymentRequest = ObjectSerializer::deserialize($request->getContent(), CreatePaymentRequest::class); $paymentRequest = $this->paymentMapper->mapCreatePaymentRequestToPaymentDTO($createPaymentRequest, $merchantId); $paymentResponse = $this->paymentService->pay($paymentRequest); $response = $this->paymentMapper->mapPaymentDTOToPaymentResponse($paymentResponse); return $this->json(ObjectSerializer::sanitizeForSerialization($response), 201); } } Payments Controller

𝕏 @maxbbeckers #[Route(name: "app_v2_payments_")] class PaymentsController extends AbstractController { public function __construct( private readonly PaymentServiceInterface $paymentService, private readonly PaymentMapper $paymentMapper ) {} #[Route('/v2/{merchantId}/payments', name: 'create_payment', methods: ['POST'])] public function create(Request $request, string $merchantId): JsonResponse { /** @var CreatePaymentRequest $createPaymentRequest */ $createPaymentRequest = ObjectSerializer::deserialize($request->getContent(), CreatePaymentRequest::class); $paymentRequest = $this->paymentMapper->mapCreatePaymentRequestToPaymentDTO($createPaymentRequest, $merchantId); $paymentResponse = $this->paymentService->pay($paymentRequest); $response = $this->paymentMapper->mapPaymentDTOToPaymentResponse($paymentResponse); return $this->json(ObjectSerializer::sanitizeForSerialization($response), 201); } } Payments Controller

𝕏 @maxbbeckers Persistence & Data

𝕏 @maxbbeckers • Each module has its own tables • Modules are not integrated at the database level (SELECTS / JOINS using tables of other modules are not allowed) 4 ways of data isolation: • Different type of persistence (e.g. MySQL, Postgres, Redis, MongoDB, …) • Separate database for each module • Separate schema for each module (used in the example) • Separate tables in the same schema (I would not recommend) Persistence & Data Rules

𝕏 @maxbbeckers Database setup API GATE WAY Payment Processing Order Management Customer Management SEPA Mandate Payment Order Customer Mandate

𝕏 @maxbbeckers Entities

𝕏 @maxbbeckers Database config .env CUSTOMER_DATABASE_URL="postgresql://customer:[email protected]:5432/customer?serverVersion=16&charset=utf8" MANDATE_DATABASE_URL="postgresql://mandate:[email protected]:5432/mandate?serverVersion=16&charset=utf8" ORDER_DATABASE_URL="postgresql://order:[email protected]:5432/order?serverVersion=16&charset=utf8" PAYMENT_DATABASE_URL="postgresql://payment:[email protected]:5432/payment?serverVersion=16&charset=utf8" Can be different for each module Can be different for each module

𝕏 @maxbbeckers Database config doctrine: dbal: connections: customer: url: '%env(resolve:CUSTOMER_DATABASE_URL)%' mandate: url: '%env(resolve:MANDATE_DATABASE_URL)%' order: url: '%env(resolve:ORDER_DATABASE_URL)%' payment: url: '%env(resolve:PAYMENT_DATABASE_URL)%' default_connection: payment orm: entity_managers: customer: connection: customer mappings: Customer: type: attribute is_bundle: false dir: '%kernel.project_dir%/src/Customer/Internal/Entity' prefix: 'App\Customer\Internal\Entity' alias: Customer

𝕏 @maxbbeckers Doctrine Migrations #config/packages/migrations/migrations_customer.yaml em: customer migrations_paths: App\Migrations\Customer: 'migrations/Customer' table_storage: table_name: migration_versions $ php bin/console doctrine:migrations:diff --em=customer --configuration=config/packages/migrations/migrations_customer.yaml Generated new migration class to "migrations/Customer/Version20240502123126.php" To run just this migration for testing purposes, you can use migrations:execute --up 'App\\Migrations\\Customer\\Version20240502123126' To revert the migration you can use migrations:execute --down 'App\\Migrations\\Customer\\Version20240502123126'

𝕏 @maxbbeckers What about queues?

𝕏 @maxbbeckers Messenger setup API GATE WAY Payment Processing Order Management Customer Management SEPA Mandate Payment Order Customer

𝕏 @maxbbeckers Queue config .env CUSTOMER_MESSENGER_TRANSPORT_DSN=amqp://customer:password@localhost:5672/customer/messages ORDER_MESSENGER_TRANSPORT_DSN=amqp://order:password@localhost:5672/order/messages PAYMENT_MESSENGER_TRANSPORT_DSN=amqp://payment:password@localhost:5672/payment/messages framework: messenger: transports: customer: dsn: '%env(CUSTOMER_MESSENGER_TRANSPORT_DSN)%' order: dsn: '%env(ORDER_MESSENGER_TRANSPORT_DSN)%' payment: dsn: '%env(PAYMENT_MESSENGER_TRANSPORT_DSN)%' routing: 'App\Customer\Message\PersistCustomerEvent': customer 'App\Order\Message\PersistOrderEvent': order 'App\Payment\Internal\Message\PersistPaymentEvent': payment

𝕏 @maxbbeckers Scaling Consumers with Supervisor $ sudo apt-get install supervisor ;/etc/supervisor/conf.d/messenger-worker-payment.conf [program:messenger-consume] command=php /home/www/bin/console messenger:consume payment --time-limit=3600 user=ubuntu numprocs=2 startsecs=0 autostart=true autorestart=true startretries=10 process_name=%(program_name)s_%(process_num)02d

𝕏 @maxbbeckers Flexibility API GATE WAY Payment Processing Order Management Customer Management SEPA Mandate

𝕏 @maxbbeckers Add a new module API GATE WAY Payment Processing Order Management Customer Management SEPA Mandate Invoicing

𝕏 @maxbbeckers Modulith is an architectural alternative between Monolith and Microservices • Simplicity & Maintainability • Low coupling & clear boundaries • Less complexity Monolith: Understanding code, Testing, Clear boundaries Microservices: Easier to configure, no network overhead The Complexity of the business code itself stays of course 😉 Summary

𝕏 @maxbbeckers Don’t start with microservices “You shouldn't start a new project with microservices, even if you're sure your application will be big enough to make it worthwhile.” Martin Fowler S

𝕏 @maxbbeckers Source: https://www.primevideotech.com/video-streaming/scaling-up-the-prime-video-audio-video-monitoring-service-and-reducing-costs-by-90

Contact: 𝕏 Thanks for your attention! @maxbbeckers [email protected] linkedin.com/in/maximilianbeckers