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Sébastien Stormacq 97b2e6d017 Add support for Lambda functions exposed behind an Application Load Balancer (ALB) (#29)
This PR adds support for exposing Swift OpenAPI Lambda functions behind
an Application Load Balancer (ALB), providing an alternative to API
Gateway for HTTP routing to Lambda functions.

## Changes

### New ALB Support
- **OpenAPILambdaALB Protocol**: New protocol for ALB integration
alongside existing API Gateway support
- **ALB Event Handling**: Added `ALBTargetGroupRequest` and
`ALBTargetGroupResponse` support
- **HTTP Request Conversion**: Extension methods to convert ALB events
to/from HTTP requests/responses

### Core Library Updates
- **ALB-related source files**: New `/Sources/ALB/` directory with
ALB-specific implementations
- **Event Type Support**: Support for `ALBTargetGroupRequest` events
from Elastic Load Balancing
- **Response Mapping**: Proper mapping from OpenAPI responses to ALB
target group responses

### Complete ALB Example
- **QuoteAPI ALB Example**: Full working example in
`Examples/quoteapi-alb/`
- **Infrastructure as Code**: Complete SAM template with VPC, subnets,
security groups, and ALB
- **Build System**: Makefile and Docker build support for ALB deployment
- **Documentation**: Comprehensive README with ALB-specific deployment
instructions

### Key Files Added
```
Sources/ALB/
├── OpenAPILambdaALB.swift
└── ALBTargetGroup+HTTPRequest.swift

Examples/quoteapi-alb/
├── Package.swift
├── template.yaml
├── Makefile
├── README.md
├── Sources/QuoteAPI/QuoteService.swift
├── Sources/QuoteAPI/openapi.yaml
├── Sources/QuoteAPI/openapi-generator-config.yaml
└── events/GetQuote.json
```

## Usage

### Simple ALB Integration
```swift
@main
struct QuoteServiceALBImpl: APIProtocol, OpenAPILambdaALB {
    func register(transport: OpenAPILambdaTransport) throws {
        try self.registerHandlers(on: transport)
    }
    
    static func main() async throws {
        let service = QuoteServiceALBImpl()
        try await service.run()
    }
    
    // Your OpenAPI implementation...
}
```

### Key Differences from API Gateway
- Uses `OpenAPILambdaALB` instead of `OpenAPILambdaHttpApi`
- Handles `ALBTargetGroupRequest` events instead of
`APIGatewayV2Request`
- Returns `ALBTargetGroupResponse` instead of `APIGatewayV2Response`
- Requires VPC infrastructure (included in SAM template)
- No built-in authorization (implement via custom middleware if needed)

## Benefits

- **Cost Optimization**: ALB can be more cost-effective for high-traffic
applications
- **VPC Integration**: Native VPC support for private network access
- **Load Balancing**: Advanced load balancing features and health checks
- **WebSocket Support**: Future WebSocket support through ALB
- **Flexibility**: Choice between API Gateway and ALB based on use case

## Testing

-  ALB example builds successfully with `sam build`
-  Local testing with `sam local invoke`
-  Complete infrastructure deployment via SAM
-  HTTP requests properly routed through ALB to Lambda
-  OpenAPI specification compatibility maintained

## Deployment

Deploy the ALB example:
```bash
cd Examples/quoteapi-alb
sam build && sam deploy --guided
```

Test the deployed endpoint:
```bash
curl http://[alb-dns-name]/stocks/AAPL
```

## Backward Compatibility

This is a purely additive change:
- Existing API Gateway implementations continue to work unchanged
- No breaking changes to existing APIs
- New ALB support is opt-in via protocol conformance
2025-10-26 09:10:09 +01:00

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1.3 KiB
Swift

// swift-tools-version: 6.0
// The swift-tools-version declares the minimum version of Swift required to build this package.
import PackageDescription
let package = Package(
name: "swift-openapi-lambda",
platforms: [.macOS(.v15)],
products: [.library(name: "OpenAPILambda", targets: ["OpenAPILambda"])],
dependencies: [
.package(url: "https://github.com/apple/swift-openapi-runtime.git", from: "1.8.2"),
.package(url: "https://github.com/awslabs/swift-aws-lambda-runtime.git", from: "2.0.0"),
.package(url: "https://github.com/awslabs/swift-aws-lambda-events.git", from: "1.2.0"),
],
targets: [
.target(
name: "OpenAPILambda",
dependencies: [
.product(name: "AWSLambdaRuntime", package: "swift-aws-lambda-runtime"),
.product(name: "AWSLambdaEvents", package: "swift-aws-lambda-events"),
.product(name: "OpenAPIRuntime", package: "swift-openapi-runtime"),
],
path: "Sources"
),
// test targets
.testTarget(
name: "OpenAPILambdaTests",
dependencies: [
.byName(name: "OpenAPILambda"),
.product(name: "AWSLambdaEvents", package: "swift-aws-lambda-events"),
]
),
]
)