Architecture¶

Understanding the core design principles and components that make Nexus a powerful plugin-based application platform.

🏗️ Architecture Overview¶

Nexus is built on a plugin-first architecture where modularity, extensibility, and performance are the primary design goals.

graph TB
    subgraph "Application Layer"
        A[FastAPI Application]
        B[Plugin Manager]
        C[Event Bus]
        D[Service Registry]
    end

    subgraph "Plugin Ecosystem"
        E[Core Plugins]
        F[Custom Plugins]
        G[Third-party Plugins]
    end

    subgraph "Infrastructure Layer"
        H[Database Adapter]
        I[Authentication Manager]
        J[Monitoring System]
        K[Configuration Manager]
    end

    A --> B
    B --> E
    B --> F
    B --> G

    E --> C
    F --> C
    G --> C

    E --> D
    F --> D
    G --> D

    A --> H
    A --> I
    A --> J
    A --> K

📖 Architecture Sections¶

Section	Description	Best For
Overview	High-level architecture and design principles	Architects, system designers
Core Components	Deep dive into framework components	Advanced developers
Event System	Event-driven communication patterns	Plugin developers
Security Model	Authentication, authorization, and security	Security engineers

🎯 Key Concepts¶

Plugin-First Design¶

Every feature in Nexus is implemented as a plugin, ensuring: - Modularity: Independent, testable components - Extensibility: Easy to add new functionality - Maintainability: Clear separation of concerns - Reusability: Plugins can be shared across projects

Event-Driven Architecture¶

Loose coupling through asynchronous events: - Publishers: Emit events when actions occur - Subscribers: React to events of interest - Event Bus: Routes events between components - Priority System: Control event processing order

Service Registry Pattern¶

Dependency injection and service discovery: - Registration: Services register themselves - Discovery: Components find needed services - Lifecycle: Automatic service management - Testing: Easy mocking and isolation

🔍 Architecture Patterns¶

Layered Architecture¶

graph TB
    A[HTTP Layer] --> B[Application Layer]
    B --> C[Business Logic Layer]
    C --> D[Data Access Layer]
    D --> E[Infrastructure Layer]

    subgraph "Cross-Cutting Concerns"
        F[Security]
        G[Logging]
        H[Monitoring]
        I[Configuration]
    end

    F -.-> A
    F -.-> B
    F -.-> C

    G -.-> A
    G -.-> B
    G -.-> C

    H -.-> A
    H -.-> B
    H -.-> C

    I -.-> A
    I -.-> B
    I -.-> C

Plugin Lifecycle¶

stateDiagram-v2
    [*] --> Discovered: Plugin Found
    Discovered --> Loading: Load Manifest
    Loading --> Loaded: Code Imported
    Loaded --> Initializing: Call initialize()
    Initializing --> Active: Success
    Initializing --> Failed: Error
    Active --> Stopping: Shutdown Signal
    Stopping --> Stopped: Cleanup Complete
    Stopped --> [*]
    Failed --> [*]

    Active --> Active: Handle Events
    Active --> Active: Process Requests

🎨 Design Principles¶

1. Convention over Configuration¶

Sensible defaults for common use cases
Minimal required configuration
Clear conventions for plugin structure
Automatic discovery and registration

2. Fail Fast, Fail Safe¶

Early validation of configuration
Graceful degradation when plugins fail
Isolation of plugin failures
Comprehensive error reporting

3. Async-First¶

Non-blocking I/O throughout
Async plugin interfaces
Event-driven communication
Scalable request handling

4. Developer Experience¶

Clear, discoverable APIs
Comprehensive documentation
Rich tooling and CLI support
Excellent error messages

🔄 Request Flow¶

sequenceDiagram
    participant C as Client
    participant F as FastAPI
    participant M as Middleware
    participant PM as Plugin Manager
    participant P as Plugin
    participant E as Event Bus
    participant S as Services

    C->>F: HTTP Request
    F->>M: Apply Middleware
    M->>PM: Route to Plugin
    PM->>P: Handle Request
    P->>E: Emit Events
    P->>S: Use Services
    S-->>P: Return Data
    E-->>P: Event Responses
    P-->>PM: Response Data
    PM-->>F: HTTP Response
    F-->>C: Send Response

🔧 System Architecture¶

Deployment Architecture¶

graph TB
    subgraph "Load Balancer"
        LB[nginx/HAProxy]
    end

    subgraph "Application Tier"
        A1[Nexus Instance 1]
        A2[Nexus Instance 2]
        A3[Nexus Instance N]
    end

    subgraph "Data Tier"
        DB[(Database)]
        CACHE[(Redis Cache)]
        FILES[File Storage]
    end

    subgraph "Monitoring"
        METRICS[Metrics Store]
        LOGS[Log Aggregation]
        ALERTS[Alerting]
    end

    LB --> A1
    LB --> A2
    LB --> A3

    A1 --> DB
    A2 --> DB
    A3 --> DB

    A1 --> CACHE
    A2 --> CACHE
    A3 --> CACHE

    A1 --> FILES
    A2 --> FILES
    A3 --> FILES

    A1 --> METRICS
    A2 --> METRICS
    A3 --> METRICS

    A1 --> LOGS
    A2 --> LOGS
    A3 --> LOGS

📊 Performance Considerations¶

Scalability Patterns¶

Horizontal scaling: Stateless application design
Vertical scaling: Efficient resource utilization
Database scaling: Read replicas and partitioning
Caching strategies: Multi-level caching hierarchy

Memory Management¶

Plugin isolation: Separate memory spaces
Resource pooling: Connection and object pools
Garbage collection: Optimized GC settings
Memory monitoring: Real-time usage tracking

I/O Optimization¶

Async operations: Non-blocking I/O
Connection pooling: Reuse database connections
Batch processing: Aggregate operations
Lazy loading: Load data on demand

🛡️ Security Architecture¶

Defense in Depth¶

graph TB
    A[Network Security] --> B[Application Security]
    B --> C[Authentication Layer]
    C --> D[Authorization Layer]
    D --> E[Data Security]
    E --> F[Audit & Monitoring]

    subgraph "Security Controls"
        G[WAF/Firewall]
        H[Rate Limiting]
        I[Input Validation]
        J[JWT Tokens]
        K[RBAC]
        L[Encryption]
        M[Logging]
    end

    A --- G
    A --- H
    B --- I
    C --- J
    D --- K
    E --- L
    F --- M

🎯 Architecture Benefits¶

For Developers¶

Fast development: Plugin templates and CLI tools
Clear boundaries: Well-defined interfaces
Easy testing: Isolated, mockable components
Rich tooling: Debug, monitor, and profile easily

For Operations¶

Scalable deployment: Horizontal and vertical scaling
Monitoring ready: Built-in metrics and health checks
Configuration management: Environment-specific configs
Zero-downtime updates: Hot-reload plugin support

For Business¶

Rapid feature delivery: Plugin-based development
Technical debt reduction: Modular architecture
Team scalability: Independent development teams
Vendor flexibility: Pluggable third-party integrations

🚀 Getting Started¶

Choose your learning path:

New to architecture? → Architecture Overview
Want to understand components? → Core Components
Building event-driven features? → Event System
Implementing security? → Security Model

Plugin Development - Build plugins with this architecture
API Reference - Use the architectural components
Deployment - Deploy this architecture

Understanding the architecture is key to building effective Nexus applications. Start with the overview to get the big picture.