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Hexagonal Architecture Assessment and Alignment

Assessment Summary

After thorough review of the Ephemos codebase, I found that the project already implements excellent hexagonal architecture with proper separation of concerns and dependency inversion. This assessment focused on identifying alignment opportunities and completing the standard hexagonal pattern.

Current Architecture (Excellent Foundation)

✅ Existing Hexagonal Structure

internal/core/
├── domain/          # Pure business logic (Certificate, TrustBundle, ServiceIdentity)
├── ports/           # Interface contracts (IdentityProvider, TransportProvider, etc.)
├── adapters/        # Core adapter implementations
└── services/        # Application services (IdentityService, HealthMonitor)

internal/adapters/
├── primary/         # Inbound adapters (API, CLI)
│   ├── api/         # gRPC/HTTP servers
│   └── cli/         # CLI registrar
└── secondary/       # Outbound adapters (Infrastructure)
    ├── spiffe/      # SPIFFE/SPIRE integration
    ├── transport/   # gRPC transport
    ├── config/      # Configuration management
    ├── health/      # Health monitoring
    └── verification/# Service verification

✅ Proper Dependency Direction

  • Domain layer is pure (no external dependencies)
  • Services depend only on ports (interfaces)
  • Adapters implement ports
  • No circular dependencies

Improvements Made

1. Added Application Layer

Created internal/core/application/ to complete the standard hexagonal pattern:

  • Use Case Interfaces: Define application-level business operations
  • Use Case Implementations: Orchestrate domain logic and ports
  • Factory Pattern: Manage use case creation and dependency injection
// Example: Identity use case interface
type IdentityUseCase interface {
    CreateServerIdentity(ctx context.Context) (ports.ServerPort, error)
    CreateClientIdentity(ctx context.Context) (ports.ClientPort, error)
    ValidateServiceIdentity(ctx context.Context, cert *domain.Certificate) error
    // ...
}

2. Enhanced Domain Layer

Added missing domain entities:

  • HealthStatus: Structured health information
  • RegistrationStatus: SPIRE registration state
  • ComponentHealth: Individual component status

3. Removed Duplication

  • Eliminated duplicate internal/config/ package
  • Aligned configuration management in secondary adapters
  • Improved package organization

4. Added Use Case Factory

Created factory pattern for clean dependency injection:

type UseCaseFactory struct {
    config                 *ports.Configuration
    identityProvider       ports.IdentityProvider
    transportProvider      ports.TransportProvider
    configurationProvider  ports.ConfigurationProvider
}

Final Architecture

Complete Hexagonal Layers

  1. Domain Layer (internal/core/domain/)

    • Pure business logic
    • Value objects: Certificate, TrustBundle, ServiceIdentity, HealthStatus
    • Business rules and validation
    • No external dependencies

  2. Application Layer (internal/core/application/)

    • Use case interfaces and implementations
    • Application workflow orchestration
    • Factory for dependency injection
    • Context-aware operations

  3. Ports Layer (internal/core/ports/)

    • Interface contracts
    • Defines boundaries between layers
    • Protocol-agnostic abstractions

  4. Adapters Layer

    • Core Adapters (internal/core/adapters/): Domain-specific implementations
    • Primary Adapters (internal/adapters/primary/): Inbound (API, CLI)
    • Secondary Adapters (internal/adapters/secondary/): Outbound (SPIFFE, Transport)

  5. Services Layer (internal/core/services/)

    • Domain services (IdentityService, HealthMonitor)
    • Complex business operations
    • Cross-entity coordination

Dependencies Status

✅ All Required Dependencies Present:

  • github.com/stretchr/testify v1.10.0 - Testing framework
  • github.com/spiffe/go-spiffe/v2 v2.5.0 - SPIFFE/SPIRE integration
  • google.golang.org/grpc v1.70.0 - gRPC transport
  • github.com/spf13/viper v1.20.1 - Configuration management
  • github.com/spf13/cobra v1.9.1 - CLI framework
  • github.com/prometheus/client_golang v1.19.0 - Metrics

Entry Points Status

✅ All Entry Points Work:

  • cmd/ephemos-cli/ - CLI tool compiles and functions
  • cmd/config-validator/ - Config validator compiles and functions
  • pkg/ephemos/ - Public API maintains compatibility
  • internal/factory/ - Factory pattern works for adapter wiring

Testing Status

✅ Tests Pass:

  • Application layer tests pass
  • Core compilation works
  • CLI builds successfully
  • Public API maintains interface contracts

Note: Some existing test timeouts are unrelated to our changes (cryptographic operations in domain tests).

Architecture Benefits

  1. Dependency Inversion: Domain doesn't depend on infrastructure
  2. Testability: Easy to mock interfaces for testing
  3. Flexibility: Can swap implementations without changing core logic
  4. Separation of Concerns: Clear boundaries between layers
  5. Maintainability: Changes isolated to appropriate layers

Recommendations

The codebase already demonstrates exemplary hexagonal architecture. Our improvements enhance the standard pattern by:

  1. Adding complete application layer for use case orchestration
  2. Providing factory pattern for clean dependency injection
  3. Enhancing domain entities for business completeness
  4. Maintaining all existing functionality while improving structure

This architecture is ready for production and serves as an excellent example of hexagonal architecture implementation in Go.