docs/developer_portal/architecture/overview.md

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title: Architecture Overview
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# Extension Architecture Overview

The Superset extension architecture is designed to be modular, secure, and performant. This document provides a comprehensive overview of how extensions work and interact with the Superset host application.

## Core Principles

### 1. Lean Core
Superset's core remains minimal, with features delegated to extensions wherever possible. Built-in features use the same APIs as external extensions, ensuring API quality through dogfooding.

### 2. Explicit Contribution Points
All extension points are clearly defined and documented. Extensions declare their capabilities in metadata files, enabling predictable lifecycle management.

### 3. Versioned APIs
Public interfaces follow semantic versioning, ensuring backward compatibility and safe evolution of the platform.

### 4. Lazy Loading
Extensions load only when needed, minimizing performance impact and resource consumption.

### 5. Composability
Architecture patterns and APIs are reusable across different Superset modules, promoting consistency.

### 6. Community-Driven
The system evolves based on real-world feedback, with new extension points added as needs emerge.

## System Architecture

```mermaid
graph TB
    subgraph "Superset Host Application"
        Core[Core Application]
        API[Extension APIs]
        Loader[Extension Loader]
        Manager[Extension Manager]
    end

    subgraph "Core Packages"
        FrontendCore["@apache-superset/core<br/>(Frontend)"]
        BackendCore["apache-superset-core<br/>(Backend)"]
        CLI["apache-superset-extensions-cli"]
    end

    subgraph "Extension"
        Metadata[extension.json]
        Frontend[Frontend Code]
        Backend[Backend Code]
        Bundle[.supx Bundle]
    end

    Core --> API
    API --> FrontendCore
    API --> BackendCore
    Loader --> Manager
    Manager --> Bundle
    Frontend --> FrontendCore
    Backend --> BackendCore
    CLI --> Bundle
```

## Key Components

### Host Application

The Superset host application provides:

- **Extension APIs**: Well-defined interfaces for extensions to interact with Superset
- **Extension Manager**: Handles lifecycle, activation, and deactivation
- **Module Loader**: Dynamically loads extension code using Webpack Module Federation
- **Security Context**: Manages permissions and sandboxing for extensions

### Core Packages

#### @apache-superset/core (Frontend)
- Shared UI components and utilities
- TypeScript type definitions
- Frontend API implementations
- Event system and command registry

#### apache-superset-core (Backend)
- Python base classes and utilities
- Database access APIs
- Security and permission helpers
- REST API registration

#### apache-superset-extensions-cli
- Project scaffolding
- Build and bundling tools
- Development server
- Package management

### Extension Structure

Each extension consists of:

- **Metadata** (`extension.json`): Declares capabilities and requirements
- **Frontend**: React components and TypeScript code
- **Backend**: Python modules and API endpoints
- **Assets**: Styles, images, and other resources
- **Bundle** (`.supx`): Packaged distribution format

## Module Federation

Extensions use Webpack Module Federation for dynamic loading:

```javascript
// Extension webpack.config.js
new ModuleFederationPlugin({
  name: 'my_extension',
  filename: 'remoteEntry.[contenthash].js',
  exposes: {
    './index': './src/index.tsx',
  },
  externals: {
    '@apache-superset/core': 'superset',
  },
  shared: {
    react: { singleton: true },
    'react-dom': { singleton: true },
  }
})
```

This allows:
- **Independent builds**: Extensions compile separately from Superset
- **Shared dependencies**: Common libraries like React aren't duplicated
- **Dynamic loading**: Extensions load at runtime without rebuilding Superset
- **Version compatibility**: Extensions declare compatible core versions

## Extension Lifecycle

### 1. Registration
```typescript
// Extension registered with host
extensionManager.register({
  name: 'my-extension',
  version: '1.0.0',
  manifest: manifestData
});
```

### 2. Activation
```typescript
// activate() called when extension loads
export function activate(context: ExtensionContext) {
  // Register contributions
  const disposables = [];

  // Add panel
  disposables.push(
    context.core.registerView('my-panel', MyPanel)
  );

  // Register command
  disposables.push(
    context.commands.registerCommand('my-command', {
      execute: () => { /* ... */ }
    })
  );

  // Store for cleanup
  context.subscriptions.push(...disposables);
}
```

### 3. Runtime
- Extension responds to events
- Provides UI components when requested
- Executes commands when triggered
- Accesses APIs as needed

### 4. Deactivation
```typescript
// Automatic cleanup of registered items
export function deactivate() {
  // context.subscriptions automatically disposed
  // Additional cleanup if needed
}
```

## Contribution Types

### Views
Extensions can add panels and UI components:

```json
{
  "views": {
    "sqllab.panels": [{
      "id": "my-panel",
      "name": "My Panel",
      "icon": "ToolOutlined"
    }]
  }
}
```

### Commands
Define executable actions:

```json
{
  "commands": [{
    "command": "my-extension.run",
    "title": "Run Analysis",
    "icon": "PlayCircleOutlined"
  }]
}
```

### Menus
Add items to existing menus:

```json
{
  "menus": {
    "sqllab.editor": {
      "primary": [{
        "command": "my-extension.run",
        "when": "editorHasSelection"
      }]
    }
  }
}
```

### API Endpoints
Register backend REST endpoints:

```python
from superset_core.api import rest_api

@rest_api.route('/my-endpoint')
def my_endpoint():
    return {'data': 'value'}
```

## Security Model

### Permissions
- Extensions run with user's permissions
- No elevation of privileges
- Access controlled by Superset's RBAC

### Sandboxing
- Frontend code runs in browser context
- Backend code runs in Python process
- Future: Optional sandboxed execution

### Validation
- Manifest validation on upload
- Signature verification (future)
- Dependency scanning

## Performance Considerations

### Lazy Loading
- Extensions load only when features are accessed
- Code splitting for large extensions
- Cached after first load

### Bundle Optimization
- Tree shaking removes unused code
- Minification reduces size
- Compression for network transfer

### Resource Management
- Automatic cleanup on deactivation
- Memory leak prevention
- Event listener management

## Development vs Production

### Development Mode
```python
# superset_config.py
ENABLE_EXTENSIONS = True
LOCAL_EXTENSIONS = ['/path/to/extension']
```
- Hot reloading
- Source maps
- Debug logging

### Production Mode
- Optimized bundles
- Cached assets
- Performance monitoring

## Future Enhancements

### Planned Features
- Enhanced sandboxing
- Extension marketplace
- Inter-extension communication
- Theme contributions
- Chart type extensions

### API Expansion
- Dashboard extensions
- Database connector API
- Security provider interface
- Workflow automation

## Best Practices

### Do's
- ✅ Use TypeScript for type safety
- ✅ Follow semantic versioning
- ✅ Handle errors gracefully
- ✅ Clean up resources properly
- ✅ Document your extension

### Don'ts
- ❌ Access private APIs
- ❌ Modify global state directly
- ❌ Block the main thread
- ❌ Store sensitive data insecurely
- ❌ Assume API stability in 0.x versions

## Learn More

- [API Reference](../api/frontend)
- [Development Guide](../getting-started)
- [Security Guidelines](./security)
- [Performance Optimization](./performance)