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swift-openapi-lambda/Examples/quoteapi-alb/template.yaml
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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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# This is an example SAM template for the purpose of this project.
# When deploying such infrastructure in production environment,
# we strongly encourage you to follow these best practices for improved security and resiliency
# - Enable access loggin on API Gateway
# See: https://docs.aws.amazon.com/apigateway/latest/developerguide/set-up-logging.html)
# - Ensure that AWS Lambda function is configured for function-level concurrent execution limit
# See: https://docs.aws.amazon.com/lambda/latest/dg/lambda-concurrency.html
# https://docs.aws.amazon.com/lambda/latest/dg/configuration-concurrency.html
# - Check encryption settings for Lambda environment variable
# See: https://docs.aws.amazon.com/lambda/latest/dg/configuration-envvars-encryption.html
# - Ensure that AWS Lambda function is configured for a Dead Letter Queue(DLQ)
# See: https://docs.aws.amazon.com/lambda/latest/dg/invocation-async-retain-records.html#invocation-dlq
# - Ensure that AWS Lambda function is configured inside a VPC when it needs to access private resources
# See: https://docs.aws.amazon.com/lambda/latest/dg/configuration-vpc.html
# Code Example: https://github.com/awslabs/swift-aws-lambda-runtime/tree/main/Examples/ServiceLifecycle%2BPostgres
AWSTemplateFormatVersion: '2010-09-09'
Transform: AWS::Serverless-2016-10-31
Description: QuoteAPI ALB Example
Resources:
QuoteServiceALB:
Type: AWS::Serverless::Function
Properties:
CodeUri: .
Handler: bootstrap
Runtime: provided.al2023
Architectures:
- arm64
MemorySize: 128
Timeout: 30
Environment:
Variables:
LOG_LEVEL: trace
Metadata:
BuildMethod: makefile
# Lambda permission for ALB
ALBLambdaInvokePermission:
Type: AWS::Lambda::Permission
Properties:
FunctionName: !GetAtt QuoteServiceALB.Arn
Action: lambda:InvokeFunction
Principal: elasticloadbalancing.amazonaws.com
# Target Group for Lambda
ALBTargetGroup:
Type: AWS::ElasticLoadBalancingV2::TargetGroup
DependsOn: ALBLambdaInvokePermission
Properties:
TargetType: lambda
Targets:
- Id: !GetAtt QuoteServiceALB.Arn
# Application Load Balancer
ApplicationLoadBalancer:
Type: AWS::ElasticLoadBalancingV2::LoadBalancer
Properties:
Scheme: internet-facing
Subnets:
- !Ref PublicSubnet1
- !Ref PublicSubnet2
SecurityGroups:
- !Ref ALBSecurityGroup
# HTTP Listener (HTTPS requires valid domain certificate)
ALBListener:
Type: AWS::ElasticLoadBalancingV2::Listener
Properties:
LoadBalancerArn: !Ref ApplicationLoadBalancer
Port: 80
Protocol: HTTP
DefaultActions:
- Type: forward
TargetGroupArn: !Ref ALBTargetGroup
# VPC for ALB
VPC:
Type: AWS::EC2::VPC
Properties:
CidrBlock: 10.0.0.0/16
EnableDnsHostnames: true
EnableDnsSupport: true
PublicSubnet1:
Type: AWS::EC2::Subnet
Properties:
VpcId: !Ref VPC
CidrBlock: 10.0.1.0/24
AvailabilityZone: !Select [0, !GetAZs '']
MapPublicIpOnLaunch: true
PublicSubnet2:
Type: AWS::EC2::Subnet
Properties:
VpcId: !Ref VPC
CidrBlock: 10.0.2.0/24
AvailabilityZone: !Select [1, !GetAZs '']
MapPublicIpOnLaunch: true
InternetGateway:
Type: AWS::EC2::InternetGateway
AttachGateway:
Type: AWS::EC2::VPCGatewayAttachment
Properties:
VpcId: !Ref VPC
InternetGatewayId: !Ref InternetGateway
RouteTable:
Type: AWS::EC2::RouteTable
Properties:
VpcId: !Ref VPC
Route:
Type: AWS::EC2::Route
DependsOn: AttachGateway
Properties:
RouteTableId: !Ref RouteTable
DestinationCidrBlock: 0.0.0.0/0
GatewayId: !Ref InternetGateway
SubnetRouteTableAssociation1:
Type: AWS::EC2::SubnetRouteTableAssociation
Properties:
SubnetId: !Ref PublicSubnet1
RouteTableId: !Ref RouteTable
SubnetRouteTableAssociation2:
Type: AWS::EC2::SubnetRouteTableAssociation
Properties:
SubnetId: !Ref PublicSubnet2
RouteTableId: !Ref RouteTable
ALBSecurityGroup:
Type: AWS::EC2::SecurityGroup
Properties:
GroupDescription: Security group for ALB
VpcId: !Ref VPC
SecurityGroupIngress:
- IpProtocol: tcp
FromPort: 80
ToPort: 80
CidrIp: 0.0.0.0/0
Outputs:
ALBUrl:
Description: Application Load Balancer URL
Value: !Sub "http://${ApplicationLoadBalancer.DNSName}/stocks/AAPL"
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