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Sebastien Stormacq
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Add a multi Source API example
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‎Examples/MultiSourceAPI/.aws-sam/build.toml‎

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# This file is auto generated by SAM CLI build command
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[function_build_definitions]
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[layer_build_definitions]

‎Examples/MultiSourceAPI/.aws-sam/build/template.yaml‎

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AWSTemplateFormatVersion: '2010-09-09'
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Transform: AWS::Serverless-2016-10-31
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Description: Multi-source API Lambda function with ALB and API Gateway V2
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Resources:
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MultiSourceAPIFunction:
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Type: AWS::Serverless::Function
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Properties:
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CodeUri: ../../.build/plugins/AWSLambdaPackager/outputs/AWSLambdaPackager/MultiSourceAPI/MultiSourceAPI.zip
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Handler: provided
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Runtime: provided.al2
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Architectures:
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- arm64
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MemorySize: 256
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Timeout: 30
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Environment:
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Variables:
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LOG_LEVEL: trace
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Events:
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ApiGatewayEvent:
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Type: HttpApi
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Properties:
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Path: /{proxy+}
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Method: ANY
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VPC:
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Type: AWS::EC2::VPC
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Properties:
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CidrBlock: 10.0.0.0/16
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EnableDnsHostnames: true
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EnableDnsSupport: true
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PublicSubnet1:
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Type: AWS::EC2::Subnet
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Properties:
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VpcId:
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Ref: VPC
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CidrBlock: 10.0.1.0/24
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AvailabilityZone:
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Fn::Select:
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- 0
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- Fn::GetAZs: ''
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MapPublicIpOnLaunch: true
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PublicSubnet2:
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Type: AWS::EC2::Subnet
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Properties:
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VpcId:
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Ref: VPC
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CidrBlock: 10.0.2.0/24
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AvailabilityZone:
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Fn::Select:
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- 1
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- Fn::GetAZs: ''
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MapPublicIpOnLaunch: true
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InternetGateway:
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Type: AWS::EC2::InternetGateway
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AttachGateway:
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Type: AWS::EC2::VPCGatewayAttachment
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Properties:
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VpcId:
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Ref: VPC
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InternetGatewayId:
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Ref: InternetGateway
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RouteTable:
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Type: AWS::EC2::RouteTable
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Properties:
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VpcId:
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Ref: VPC
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Route:
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Type: AWS::EC2::Route
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DependsOn: AttachGateway
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Properties:
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RouteTableId:
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Ref: RouteTable
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DestinationCidrBlock: '0.0.0.0/0'
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GatewayId:
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Ref: InternetGateway
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SubnetRouteTableAssociation1:
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Type: AWS::EC2::SubnetRouteTableAssociation
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Properties:
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SubnetId:
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Ref: PublicSubnet1
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RouteTableId:
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Ref: RouteTable
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SubnetRouteTableAssociation2:
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Type: AWS::EC2::SubnetRouteTableAssociation
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Properties:
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SubnetId:
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Ref: PublicSubnet2
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RouteTableId:
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Ref: RouteTable
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ALBSecurityGroup:
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Type: AWS::EC2::SecurityGroup
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Properties:
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GroupDescription: Security group for ALB
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VpcId:
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Ref: VPC
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SecurityGroupIngress:
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- IpProtocol: tcp
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FromPort: 80
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ToPort: 80
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CidrIp: '0.0.0.0/0'
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ApplicationLoadBalancer:
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Type: AWS::ElasticLoadBalancingV2::LoadBalancer
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Properties:
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Scheme: internet-facing
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Subnets:
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- Ref: PublicSubnet1
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- Ref: PublicSubnet2
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SecurityGroups:
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- Ref: ALBSecurityGroup
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ALBTargetGroup:
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Type: AWS::ElasticLoadBalancingV2::TargetGroup
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DependsOn: ALBLambdaInvokePermission
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Properties:
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TargetType: lambda
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Targets:
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- Id:
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Fn::GetAtt:
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- MultiSourceAPIFunction
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- Arn
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ALBListener:
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Type: AWS::ElasticLoadBalancingV2::Listener
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Properties:
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LoadBalancerArn:
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Ref: ApplicationLoadBalancer
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Port: 80
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Protocol: HTTP
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DefaultActions:
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- Type: forward
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TargetGroupArn:
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Ref: ALBTargetGroup
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ALBLambdaInvokePermission:
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Type: AWS::Lambda::Permission
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Properties:
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FunctionName:
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Fn::GetAtt:
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- MultiSourceAPIFunction
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- Arn
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Action: lambda:InvokeFunction
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Principal: elasticloadbalancing.amazonaws.com
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Outputs:
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ApiGatewayUrl:
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Description: API Gateway endpoint URL
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Value:
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Fn::Sub: https://${ServerlessHttpApi}.execute-api.${AWS::Region}.amazonaws.com
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ALBUrl:
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Description: Application Load Balancer URL
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Value:
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Fn::Sub: http://${ApplicationLoadBalancer.DNSName}

‎Examples/MultiSourceAPI/.gitignore‎

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.DS_Store
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/.build
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/Packages
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xcuserdata/
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DerivedData/
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.swiftpm/configuration/registries.json
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.swiftpm/xcode/package.xcworkspace/contents.xcworkspacedata
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.netrc
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Package.resolved

‎Examples/MultiSourceAPI/Package.swift‎

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// swift-tools-version:6.2
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import PackageDescription
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// needed for CI to test the local version of the library
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import struct Foundation.URL
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let package = Package(
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name: "MultiSourceAPI",
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platforms: [.macOS(.v15)],
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products: [
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.executable(name: "MultiSourceAPI", targets: ["MultiSourceAPI"])
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],
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dependencies: [
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.package(url: "https://github.com/awslabs/swift-aws-lambda-runtime.git", from: "2.0.0"),
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.package(url: "https://github.com/awslabs/swift-aws-lambda-events.git", from: "1.0.0"),
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],
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targets: [
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.executableTarget(
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name: "MultiSourceAPI",
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dependencies: [
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.product(name: "AWSLambdaRuntime", package: "swift-aws-lambda-runtime"),
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.product(name: "AWSLambdaEvents", package: "swift-aws-lambda-events"),
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],
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path: "Sources"
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)
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]
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)
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if let localDepsPath = Context.environment["LAMBDA_USE_LOCAL_DEPS"],
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localDepsPath != "",
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let v = try? URL(fileURLWithPath: localDepsPath).resourceValues(forKeys: [.isDirectoryKey]),
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v.isDirectory == true
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{
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let indexToRemove = package.dependencies.firstIndex { dependency in
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if case .sourceControl(
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name: _,
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location: "https://github.com/awslabs/swift-aws-lambda-runtime.git",
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requirement: _
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) = dependency.kind {
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return true
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}
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return false
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}
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if let indexToRemove {
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package.dependencies.remove(at: indexToRemove)
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}
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print("[INFO] Compiling against swift-aws-lambda-runtime located at \(localDepsPath)")
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package.dependencies += [
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.package(name: "swift-aws-lambda-runtime", path: localDepsPath)
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]
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}

‎Examples/MultiSourceAPI/README.md‎

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# Multi-Source API Example
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This example demonstrates a Lambda function that handles requests from both Application Load Balancer (ALB) and API Gateway V2 by accepting a raw `ByteBuffer` and decoding the appropriate event type.
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## Overview
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The Lambda handler receives events as `ByteBuffer` and attempts to decode them as either:
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- `ALBTargetGroupRequest` - for requests from Application Load Balancer
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- `APIGatewayV2Request` - for requests from API Gateway V2
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Based on the successfully decoded type, it returns an appropriate response.
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## Building
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```bash
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swift package archive --allow-network-connections docker
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```
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## Deploying
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Deploy using SAM:
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```bash
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sam deploy \
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--resolve-s3 \
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--template-file template.yaml \
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--stack-name MultiSourceAPI \
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--capabilities CAPABILITY_IAM
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```
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## Testing
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After deployment, SAM will output two URLs:
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### Test API Gateway V2:
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```bash
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curl https://<api-id>.execute-api.<region>.amazonaws.com/apigw/test
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```
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Expected response:
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```json
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{"source":"APIGatewayV2","path":"/apigw/test"}
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```
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### Test ALB:
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```bash
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curl http://<alb-dns-name>/alb/test
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```
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Expected response:
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```json
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{"source":"ALB","path":"/alb/test"}
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```
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## How It Works
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The handler uses Swift's type-safe decoding to determine the event source:
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1. Receives raw `ByteBuffer` event
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2. Attempts to decode as `ALBTargetGroupRequest`
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3. If that fails, attempts to decode as `APIGatewayV2Request`
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4. Returns appropriate response based on the decoded type
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5. Throws error if neither decoding succeeds
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This pattern is useful when a single Lambda function needs to handle requests from multiple sources.

‎Examples/MultiSourceAPI/Sources/main.swift‎

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import AWSLambdaEvents
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import AWSLambdaRuntime
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import HTTPTypes
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import NIOCore
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#if canImport(FoundationEssentials)
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import FoundationEssentials
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#else
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import Foundation
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#endif
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struct MultiSourceHandler: StreamingLambdaHandler {
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func handle(
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_ event: ByteBuffer,
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responseWriter: some LambdaResponseStreamWriter,
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context: LambdaContext
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) async throws {
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let decoder = JSONDecoder()
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let data = Data(event.readableBytesView)
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// Try to decode as ALBTargetGroupRequest first
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if let albRequest = try? decoder.decode(ALBTargetGroupRequest.self, from: data) {
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context.logger.info("Received ALB request to path: \(albRequest.path)")
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let response = ALBTargetGroupResponse(
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statusCode: .ok,
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headers: ["Content-Type": "application/json"],
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body: "{\"source\":\"ALB\",\"path\":\"\(albRequest.path)\"}"
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)
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let encoder = JSONEncoder()
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let responseData = try encoder.encode(response)
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try await responseWriter.write(ByteBuffer(bytes: responseData))
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try await responseWriter.finish()
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return
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}
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// Try to decode as APIGatewayV2Request
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if let apiGwRequest = try? decoder.decode(APIGatewayV2Request.self, from: data) {
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context.logger.info("Received API Gateway V2 request to path: \(apiGwRequest.rawPath)")
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let response = APIGatewayV2Response(
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statusCode: .ok,
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headers: ["Content-Type": "application/json"],
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body: "{\"source\":\"APIGatewayV2\",\"path\":\"\(apiGwRequest.rawPath)\"}"
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)
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let encoder = JSONEncoder()
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let responseData = try encoder.encode(response)
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try await responseWriter.write(ByteBuffer(bytes: responseData))
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try await responseWriter.finish()
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return
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}
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// Unknown event type
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context.logger.error("Unable to decode event as ALB or API Gateway V2 request")
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throw LambdaError.invalidEvent
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}
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}
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enum LambdaError: Error {
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case invalidEvent
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}
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let runtime = LambdaRuntime(handler: MultiSourceHandler())
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try await runtime.run()

‎Examples/MultiSourceAPI/samconfig.toml‎

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version = 0.1
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[default.deploy.parameters]
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stack_name = "sam-app"
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resolve_s3 = true
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s3_prefix = "sam-app"
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region = "eu-west-3"
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capabilities = "CAPABILITY_IAM"
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image_repositories = []
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[default.global.parameters]
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region = "eu-west-3"

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