Swift Lambda API

This project is part of the Swift in the Cloud Series to demonstrate the basics of building a Swift based Lambda API that can requests from multiple regions. To successfully complete the steps below, you should start at the beginning of this series with the AWS Swift Multi-Region API project.

Requirements

To complete this setup you will need:

1. Xcode 14+
2. Docker 4+
3. AWS CLI (setup to access the AWS account used in the AWS Swift Multi-Region API project)

Getting Started

This code will build a Swift ARM package for Graviton Lambda instances by default.

Installation

1. Create a bucket for the project in AWS S3 in the same region you began installing your Cloudformation stacks. swiftdemo0 will be translated by the Cloudformation template as swiftlambda-region. Eg: if swiftlambda is set at the template bucketname, then swiftlambda-us-east-2 will be the bucket name the Cloudformation template looks for in us-east-2 (Ohio).
2. Clone SwiftLambdaAPI locally
3. Make sure docker is running
4. From the command line change directories into the project.
5. Run ./build.sh. To change the available options run ./build.sh -h
6. Run ./package.sh. To change the available options run `./package.sh -h

cd SwiftLambdaAPI/

# Build SwiftLambdaAPI
# Available Swift AmazonLinux2 versions: https://hub.docker.com/_/swift/?tab=tags
./build.sh -v 5.7.2 -a linux/arm64

# Package SwiftLambdaAPI for upload to S3
./package.sh -n SwiftLambdaAPI

# Upload to S3 via AWS CLI.
# NB: You can also just upload the file lambda.zip via the AWS S3 Console
aws s3 cp .build/lambda/SwiftLamdbaAPI/lambda.zip s3://swiftdemo0-us-east-2/SwiftLamdbaAPI/

Make a note of the final keyPath of the upload. You will need this for the AWS Swift Multi-Region API CloudFormation template.

Package Dependencies

This project makes use of:

• Swift AWS Runtime — AWS Lambda Runtime API implementation in Swift

Testing Locally

You can also build and run this code locally in Xcode. To do this you will need to set an environment variable to enable the lambda server to run locally. Use Xcode's scheme editor to add environment variables to your app. In the Xcode menu, go to Product > Scheme > Edit Scheme. Select Run on the left, select Arguments in the main window. Under Environment Variables add Name: LOCAL_LAMBDA_SERVER_ENABLED, Value: true.

Build and run the project and you should see Output similar to the following:

2023-01-10T16:01:11-0500 info LocalLambdaServer : [AWSLambdaRuntimeCore] LocalLambdaServer started and listening on 127.0.0.1:7000, receiving events on /invoke
2023-01-10T16:01:11-0500 info Lambda : [AWSLambdaRuntimeCore] lambda lifecycle startingwith Configuration
	General(logLevel: info))
	Lifecycle(id: 24655414529708, maxTimes: 0, stopSignal: TERM)
RuntimeEngine(ip: 127.0.0.1, port: 7000, requestTimeout: nil

This allows you to POST requests to 127.0.0.1 (localhost) on port 7000 and have the lambda response. The format of these requests, is expected to be in the same format (version 2.0) that APIGateway uses to talk to the Lambda.

For testing you can copy the example below and use it locally. The minimum changes that need to be made from the AWS v2.0 default are to the requestContext > http dictionary. method and path will be used when the request hits the locally run instance. In this example, method is set to GET and path is set to /hello to get the success response of a JSON encoded HelloResponse. Change either method or path and see how the code responds (404). The response format is also not your typical HTTP response as it is formatted for the APIGateway service which will transform it into the expected user response. From the command line you can run this test via curl.

## SwiftLambdaAPI (POST) local 
curl -X "POST" "http://localhost:7000/invoke" \
     -H 'Content-Type: application/json' \
     -d $'{
  "version": "2.0",
  "routeKey": "$default",
  "rawPath": "/my/path",
  "rawQueryString": "parameter1=value1&parameter1=value2&parameter2=value",
  "cookies": [
    "cookie1",
    "cookie2"
  ],
  "headers": {
    "header1": "value1",
    "header2": "value1,value2"
  },
  "queryStringParameters": {
    "parameter1": "value1,value2",
    "parameter2": "value"
  },
  "requestContext": {
    "accountId": "123456789012",
    "apiId": "api-id",
    "authentication": {
      "clientCert": {
        "clientCertPem": "CERT_CONTENT",
        "subjectDN": "www.example.com",
        "issuerDN": "Example issuer",
        "serialNumber": "a1:a1:a1:a1:a1:a1:a1:a1:a1:a1:a1:a1:a1:a1:a1:a1",
        "validity": {
          "notBefore": "May 28 12:30:02 2019 GMT",
          "notAfter": "Aug  5 09:36:04 2021 GMT"
        }
      }
    },
    "authorizer": {
      "jwt": {
        "claims": {
          "claim1": "value1",
          "claim2": "value2"
        },
        "scopes": [
          "scope1",
          "scope2"
        ]
      }
    },
    "domainName": "id.execute-api.us-east-1.amazonaws.com",
    "domainPrefix": "id",
    "http": {
      "method": "GET",
      "path": "/hello",
      "protocol": "HTTP/1.1",
      "sourceIp": "192.0.2.1",
      "userAgent": "agent"
    },
    "requestId": "id",
    "routeKey": "$default",
    "stage": "$default",
    "time": "12/Mar/2020:19:03:58 +0000",
    "timeEpoch": 1583348638390
  },
  "body": "Hello from Lambda",
  "pathParameters": {
    "parameter1": "value1"
  },
  "isBase64Encoded": false,
  "stageVariables": {
    "stageVariable1": "value1",
    "stageVariable2": "value2"
  }
}'

Next Steps

As mentioned above this project is part of the Swift in the Cloud Series. The next step is to go back the AWS Swift Multi-Region API and complete the SwiftLambdaAPI lambda template stack with the parameter data generated here.

Further Improvements

Time will bring changes to this project. To really make this setup robust, it can be improved by adding:

1. Testing is ignored in this project. As it develops testing may become more relevant.
2. Simpler build and packaging scripting
3. Better automation via the AWS CLI

License

SwiftLambdaAPI is released under the Apache License, Version 2.0. See LICENSE for details.