This library provides an AWS Lambda transport for Swift OpenAPI generator
This library allows to expose server side Swift OpenAPI implementation generated by the Swift OpenAPI generator as an AWS Lambda function.
The library provides two capabilities:
- a default implementation of an AWS Lambda function that consumes your OpenAPI service implementation
- a binding with the Amazon API Gateway (HTTP API mode) (aka
APIGatewayV2) event type.
Other Lambda function bindings (event types) are supported as well, depending on your needs. We include instructions to create a binding with an Amazon API Gateway (REST API mode)
To write and deploy AWS Lambda functions based on an OpenAPI API definition, you need the following:
- an AWS Account
- the AWS Command Line Interface (AWS CLI) - install the CLI and configure it with credentials to your AWS account
- the AWS SAM CLI - a command-line tool used to create serverless workloads on AWS
- the Docker Desktop - to compile your Swift code for Linux deployment to AWS Lambda
If you already have an OpenAPI definition, you already generated the server stubs, and wrote an implementation, here are the additional steps to expose your OpenAPI service implementation as a AWS Lambda function and an Amazon API Gateway HTTP API (aka APIGatewayV2).
If you don't know how to start, read the next section, there is a tutorial with step-by-step instructions.
To expose your OpenAPI implementation as an AWS Lambda function:
-
Add the dependency to your
Package.swiftThe project dependencies:
dependencies: [ .package(url: "https://github.com/apple/swift-openapi-generator.git", from: "1.0.0"), .package(url: "https://github.com/apple/swift-openapi-runtime.git", from: "1.0.0"), // add these three dependencies .package(url: "https://github.com/swift-server/swift-aws-lambda-runtime.git", from: "1.0.0-alpha.1"), .package(url: "https://github.com/swift-server/swift-aws-lambda-events.git", from: "0.1.0"), .package(url: "https://github.com/sebsto/swift-openapi-lambda", from: "0.1.1") ],The target dependencies:
.executableTarget( name: "YourOpenAPIService", dependencies: [ .product(name: "OpenAPIRuntime",package: "swift-openapi-runtime"), // add these three dependencies .product(name: "AWSLambdaRuntime", package: "swift-aws-lambda-runtime"), .product(name: "AWSLambdaEvents", package: "swift-aws-lambda-events"), .product(name: "OpenAPILambda",package: "swift-openapi-lambda"), ],- Add a protocol and a constructor to your existing OpenAPI service implementation
There are only four changes to make to your existing implementation:
import Foundation import OpenAPIRuntime import OpenAPILambda // <-- 1. import this library @main // <-- 2. flag this struct as the executable target entrypoint struct QuoteServiceImpl: APIProtocol, OpenAPILambdaHttpApi { // <-- 3. add the OpenAPILambdaHttpApi protocol init(transport: OpenAPILambdaTransport) throws { // <-- 4. add this constructor (don't remove the call to `registerHandlers(on:)`) try self.registerHandlers(on: transport) } // the rest below is unmodified func getQuote(_ input: Operations.getQuote.Input) async throws -> Operations.getQuote.Output { let symbol = input.path.symbol let price = Components.Schemas.quote( symbol: symbol, price: Double.random(in: 100..<150).rounded(), change: Double.random(in: -5..<5).rounded(), changePercent: Double.random(in: -0.05..<0.05), volume: Double.random(in: 10000..<100000).rounded(), timestamp: Date()) return .ok(.init(body: .json(price))) } }- Package and deploy your Lambda function + create an HTTP API Gateway (aka
APIGatewayV2)
🎉 Enjoy!
- Create a Swift executable project
mkdir quoteapi && cd quoteapi swift package init --name quoteapi --type executable- Write or import an OpenAI API definition in YAML or JSON
# # the $ signs are escaped (\$) to work with the cat << EOF command # if you choose to copy the content directly to a text editor, # be sure to remove the \ (that means \$ becomes $) #cat << EOF > Sources/openapi.yaml openapi: 3.1.0 info: title: StockQuoteService version: 1.0.0 components: schemas: quote: type: object properties: symbol: type: string price: type: number change: type: number changePercent: type: number volume: type: number timestamp: type: string format: date-time paths: /stocks/{symbol}: get: summary: Get the latest quote for a stock operationId: getQuote parameters: - name: symbol in: path required: true schema: type: string tags: - stocks responses: 200: description: OK content: application/json: schema: \$ref: '#/components/schemas/quote' 400: description: Bad Request 404: description: Not Found EOF- Add a Swift OpenAPI generator configuration file to generate only the server side
cat << EOF > Sources/openapi-generator-config.yaml generate: - types - server EOF- Use this
Package.swiftfile to define targets and their dependencies
cat << EOF > Package.swift // swift-tools-version: 5.9 // The swift-tools-version declares the minimum version of Swift required to build this package. import PackageDescription let package = Package( name: "QuoteService", platforms: [ .macOS(.v13), .iOS(.v15), .tvOS(.v15), .watchOS(.v6), ], products: [ .executable(name: "QuoteService", targets: ["QuoteService"]), ], dependencies: [ .package(url: "https://github.com/apple/swift-openapi-generator.git", from: "1.0.0"), .package(url: "https://github.com/apple/swift-openapi-runtime.git", from: "1.0.0"), .package(url: "https://github.com/swift-server/swift-aws-lambda-runtime.git", from: "1.0.0-alpha.1"), .package(url: "https://github.com/swift-server/swift-aws-lambda-events.git", from: "0.1.0"), .package(url: "https://github.com/sebsto/swift-openapi-lambda", from: "0.1.1") ], targets: [ .executableTarget( name: "QuoteService", dependencies: [ .product(name: "AWSLambdaRuntime", package: "swift-aws-lambda-runtime"), .product(name: "AWSLambdaEvents", package: "swift-aws-lambda-events"), .product(name: "OpenAPIRuntime",package: "swift-openapi-runtime"), .product(name: "OpenAPILambda",package: "swift-openapi-lambda"), ], path: "Sources", resources: [ .copy("openapi.yaml"), .copy("openapi-generator-config.yaml") ], plugins: [ .plugin( name: "OpenAPIGenerator", package: "swift-openapi-generator" ) ] ), ] ) EOF- Generate server side Swift stub of the OpenAPI API definition
swift build- Replace
main.swiftwith your own implementation
rm Sources/main.swift cat << EOF > Sources/QuoteService.swift import Foundation import OpenAPIRuntime import OpenAPILambda @main struct QuoteServiceImpl: APIProtocol, OpenAPILambdaHttpApi { init(transport: OpenAPILambdaTransport) throws { try self.registerHandlers(on: transport) } func getQuote(_ input: Operations.getQuote.Input) async throws -> Operations.getQuote.Output { let symbol = input.path.symbol let price = Components.Schemas.quote( symbol: symbol, price: Double.random(in: 100..<150).rounded(), change: Double.random(in: -5..<5).rounded(), changePercent: Double.random(in: -0.05..<0.05), volume: Double.random(in: 10000..<100000).rounded(), timestamp: Date()) return .ok(.init(body: .json(price))) } } EOF- Build the project to ensure everything works
swift build- Add the Lambda build instructions as a Docker file and a Makefile. We build for Swift 5.9 on Amazon Linux 2
# # the $ signs are escaped (\$) to work with the cat << EOF command # if you choose to copy the content directly to a text editor, # be sure to remove the \ (that means \$ becomes $) #cat << EOF > Dockerfile # image used to compile your Swift code FROM public.ecr.aws/docker/library/swift:5.9.1-amazonlinux2 RUN yum -y install git jq tar zip openssl-devel EOF cat << EOF > Makefile ### Add functions here and link them to builder-bot format MUST BE "build-FunctionResourceName in template.yaml" build-QuoteService: builder-bot # Helper commands deploy: sam deploy logs: sam logs --stack-name QuoteService --name QuoteService tail: sam logs --stack-name QuoteService --name QuoteService --tail ###################### No Change required below this line ########################## builder-bot: \$(eval \$@PRODUCT = \$(subst build-,,\$(MAKECMDGOALS))) \$(eval \$@BUILD_DIR = \$(PWD)/.aws-sam/build-swift) \$(eval \$@STAGE = \$(\$@BUILD_DIR)/lambda) \$(eval \$@ARTIFACTS_DIR = \$(PWD)/.aws-sam/build/\$(\$@PRODUCT)) # build docker image to compile Swift for Linux docker build -f Dockerfile . -t swift-builder # prep directories mkdir -p \$(\$@BUILD_DIR)/lambda \$(\$@ARTIFACTS_DIR) # compile application inside Docker image using source code from local project folder docker run --rm -v \$(\$@BUILD_DIR):/build-target -v \`pwd\`:/build-src -w /build-src swift-builder bash -cl "swift build --static-swift-stdlib --product \$(\$@PRODUCT) -c release --build-path /build-target" # create lambda bootstrap file docker run --rm -v \$(\$@BUILD_DIR):/build-target -v \`pwd\`:/build-src -w /build-src swift-builder bash -cl "cd /build-target/lambda && ln -s \$(\$@PRODUCT) /bootstrap" # copy binary to stage cp \$(\$@BUILD_DIR)/release/\$(\$@PRODUCT) \$(\$@STAGE)/bootstrap # copy app from stage to artifacts dir cp \$(\$@STAGE)/* \$(\$@ARTIFACTS_DIR) EOF- Add a SAM template to deploy the Lambda function and the API Gateway
# # the $ signs are escaped (\$) to work with the cat << EOF command # if you choose to copy the content directly to a text editor, # be sure to remove the \ (that means \$ becomes $) #cat << EOF > template.yml AWSTemplateFormatVersion: '2010-09-09' Transform: AWS::Serverless-2016-10-31 Description: SAM Template for QuoteService Globals: Function: Timeout: 60 CodeUri: . Handler: swift.bootstrap Runtime: provided.al2 MemorySize: 512 Architectures: - arm64 Resources: # Lambda function QuoteService: Type: AWS::Serverless::Function Properties: Events: # pass through all HTTP verbs and paths Api: Type: HttpApi Properties: Path: /{proxy+} Method: ANY Metadata: BuildMethod: makefile # print API endpoint and name of database table Outputs: SwiftAPIEndpoint: Description: "API Gateway endpoint URL for your application" Value: !Sub "https://\${ServerlessHttpApi}.execute-api.\${AWS::Region}.amazonaws.com" EOF- Build the Lambda function executable for Amazon Linux 2
sam build- Deploy the Lambda function and create an API Gateway in front of it
# use --guided for the first deployment only. # SAM cli collects a few parameters and store them in `samconfig.toml` sam deploy --guided --stack-name QuoteServiceAccept all the default values, except:
QuoteService has no authentication. Is this okay? [y/N]: <-- answer Y here This command outputs the URL of the API Gateway, for example:
Outputs ----------------------------------------------------------------------------------------------------------------------------- Key SwiftAPIEndpoint Description API Gateway endpoint URL for your application Value https://747ukfmah7.execute-api.us-east-1.amazonaws.com ------------------------------------------------------------------------------------------------------------------------------ Test your setup
curl [[ Replace with SWIFTAPIEndpoint value ]]/stocks/AAPL { "change" : -4, "changePercent" : -0.030052760210257923, "price" : 111, "symbol" : "AAPL", "timestamp" : "2023-12-13T03:12:35Z", "volume" : 63812 }On new AWS accounts, there is no costs associated with the deployment and test of this sample code, up to 1 million invocation per month. It falls under the permananet AWS free Tier for AWS Lambda and Amazon API Gateway
When you're account is older than a year, you are charged $1.0 per million calls to the API Gateway. AWS Lambda function invocation stays free up to 4 million invocations and 400.000 GB-second compute time per month.
To delete the AWS Lambda function, the API Gateway, and the roles and permissions created with sam, just type:
sam deletegit clone https://github.com/sebsto/swift-openapi-lambda.git && cd swift-openapi-lambda # In the directory of the Swift OpenAPI Lambda transport project LOCAL_LAMBDA_SERVER_ENABLED=true swift run # from another terminal, in the directory of the QuoteAPI sample project curl -v -X POST --header "Content-Type: application/json" --data @events/GetQuote.json http://127.0.0.1:7000/invoke When you expose your AWS Lambda function to other event types, you have to specialize the OpenAPILambda protocol and implement the two methods that transform your Lambda function input data to an OpenAPIRequest and the other way around, transform an OpenAPIResponse to your Lambda function output type.
Here is an example with the Amazon API Gateway (Rest Api), (aka the original API Gateway).
I start with an OpenAPI stub implementation - unmodified.
import Foundation import OpenAPIRuntime struct QuoteServiceImpl: APIProtocol { func getQuote(_ input: Operations.getQuote.Input) async throws -> Operations.getQuote.Output { let symbol = input.path.symbol let price = Components.Schemas.quote( symbol: symbol, price: Double.random(in: 100..<150).rounded(), change: Double.random(in: -5..<5).rounded(), changePercent: Double.random(in: -0.05..<0.05), volume: Double.random(in: 10000..<100000).rounded(), timestamp: Date()) return .ok(.init(body: .json(price))) } }Next, I implement a struct that conforms to OpenAPILambda. This struct defines:
- the event input and output the Lambda function will work on (from AWS Lambda Event Types library).
- the mandatory constructor
init(transport:) - the executable target entrypoint (
@main)
Here is an example using APIGatewayRequest and APIGatewayResponse:
@main struct QuoteServiceLambda: OpenAPILambda { typealias Event = APIGatewayRequest typealias Output = APIGatewayResponse public init(transport: OpenAPILambdaTransport) throws { let openAPIHandler = QuoteServiceImpl() try openAPIHandler.registerHandlers(on: transport) } }Next step is to implement two methods from OpenAPILambda protocol to convert your Lambda function input data (APIGatewayRequest) to an OpenAPIRequest and the other way around, transform an OpenAPIResponse to your Lambda function output type (APIGatewayResponses).
extension OpenAPILambda where Event == APIGatewayRequest { /// Transform a Lambda input (`APIGatewayRequest` and `LambdaContext`) to an OpenAPILambdaRequest (`HTTPRequest`, `String?`) public func request(context: LambdaContext, from request: Event) throws -> OpenAPILambdaRequest { (try request.httpRequest(), request.body) } } extension OpenAPILambda where Output == APIGatewayResponse { /// Transform an OpenAPI response (`HTTPResponse`, `String?`) to a Lambda Output (`APIGatewayResponse`) public func output(from response: OpenAPILambdaResponse) -> Output { var apiResponse = APIGatewayResponse(from: response.0) apiResponse.body = response.1 return apiResponse } }To keep the above code short, simple, and readable, we suggest to implement whatever extension on the Lambda source Event type. Here are the extensions required to support the above code. These are simple data transformation methods from one type to the other.
extension APIGatewayRequest { /// Return an `HTTPRequest.Method` for this `APIGatewayRequest` public func httpRequestMethod() throws -> HTTPRequest.Method { guard let method = HTTPRequest.Method(rawValue: self.httpMethod.rawValue) else { throw OpenAPILambdaHttpError.invalidMethod(self.httpMethod.rawValue) } return method } /// Return an `HTTPRequest` for this `APIGatewayV2Request` public func httpRequest() throws -> HTTPRequest { try HTTPRequest( method: self.httpRequestMethod(), scheme: "https", authority: "", path: self.path, headerFields: self.headers.httpFields() ) } } extension APIGatewayResponse { /// Create a `APIGatewayV2Response` from an `HTTPResponse` public init(from response: HTTPResponse) { self = APIGatewayResponse( statusCode: .init(code: UInt(response.status.code)), headers: .init(from: response.headerFields), isBase64Encoded: false ) } }You can apply the same design to support other AWS Lambda event types. However, keep in mind that the OpenAPILAmbda implementation is heavily biased towards receiving, routing, and responding to HTTP requests.
To get started with the Swift OpenAPI generator, check out the full documentation, which contains a step-by-step tutorial.
The Swift Runtime for AWS Lambda allows you to write AWS Lambda functions in the Swift programming language.
To get started, check out this step-by-step tutorial and the documentation.
Read "What is SAM" to understand and get started with SAM.