Software Architecture Hexagonal

Hexagonal Architecture

archetypes: tactical, educational anti_triggers: tightly coupled design response_profile: verbosity: medium directive_strength: high abstraction_level: tactical

Guides the implementation of hexagonal (ports and adapters) architecture, focusing on best practices for decoupling business logic from external concerns.

When to Use

• When you need a flexible architecture that accommodates changes easily.
• For applications with complex domain logic.
• When you need to integrate multiple external systems.

Core Workflow

1. Define the Domain Model – Centralize your core domain logic.
2. Establish Ports – Create interfaces for external services and applications.
3. Implement Adapters – Build adapters to connect the domain to outside technology.

Implementation Patterns

Enhanced Examples of Hexagonal Architecture

1. Core Domain Logic Implementation:

   # Example demonstrating core domain logic separate from infrastructure
   class Account:
       def __init__(self, id, balance):
           self.id = id
           self.balance = balance
   
   class AccountService:
       def __init__(self, repository):
           self.repository = repository
   
       def create_account(self, id, initial_balance):
           account = Account(id, initial_balance)
           self.repository.save(account)
   

2. Establishing Ports and Adapters:

   # Defining an Adapter for external service interactions
   class PaymentProcessor:
       def process_payment(self, account_id, amount):
           # Logic to process payment through an external API
           print(f'Processing payment of {amount} for account {account_id}')
   

3. Integration Example:

   # Example showing integration with external services via adapters
   payments:
     url: http://payment-service/api
     description: Service to handle payment processing
   

Real-World Applications

• Discuss examples of how organizations like Netflix and Uber implement hexagonal architecture for scalability and maintainability.
• Provide insights into trade-offs between hexagonal architecture and other architectural styles such as layered architecture or microservices.

Pattern 1: Central Domain Logic

class Product:
    def __init__(self, name, price):
        self.name = name
        self.price = price

class ProductService:
    def add_product(self, product):
        # Add logic for adding the product
        pass

# Adapter example
class ExternalServiceAdapter:
    def call_service(self):
        # Logic to interact with an external service
        pass

Constraints

MUST DO

• Ensure clear separations of concerns.
• Use automated tests to validate interactions.

MUST NOT DO

• Allow direct dependencies from the domain to external services.
• Mix external framework concerns with core logic in the same layer.