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Build and deploy Swift Package Manager projects on AWS Lambda.

swift lambda builds Swift projects using the Swift AWS Lambda Runtime for deployment into AWS Lambda functions. It uses a Swift cross compilation toolchain for Amazon Linux to build the project right on macOS, no Docker required. Simply call swift lambda build.

A built Swift lambda can then be deployed using swift lambda deploy (using either aws lambda publish or sam deploy).

Blog article: Deploying Swift on AWS Lambda.

Note: Due to a bug in Xcode 11's Swift 5.2.4, a Swift 5.3 install (e.g. Xcode beta 12) is currently required.

First make sure swift --version shows a 5.3 release, it is currently required.

swift lambda is easiest to install using Homebrew, get it over here.

This single call installs swift lambda and all its dependencies:

$ brew install SPMDestinations/tap/swift-lambda

It's a pretty big download at over 1GB (binary host & target Swift toolchains from Swift.org and the AWS CLI).

A simple Swift Lambda using Macro.

Setup the Swift package:

mkdir HelloWorld && cd HelloWorld
swift package init --type executable
open Package.swift # opens Xcode

Configure the Package.swift to look like this:

// swift-tools-version:5.2
import PackageDescription

let package = Package(
  name         : "HelloWorld",
  platforms    : [ .macOS(.v10_13) ], // <== add this
  dependencies : [ // and add this dependency ↓
    .package(url: "https://github.com/Macro-swift/MacroLambda.git",
             from: "0.1.3"),
    .package(url: "https://github.com/AlwaysRightInstitute/cows.git",
             from: "1.0.0") // optional but fun
  ],
  targets: [
    .target(name: "HelloWorld", 
            dependencies: [ "MacroLambda", "cows" ])
  ]
)

Fill in the Lambda's code in the main.swift:

import MacroLambda

let app = Express()
app.use(bodyParser.text())

app.post("/hello") { req, res, next in
  res.send("Client sent: \(req.body.text ?? "~nothing~")")
}

app.get { req, res, next in
  res.send("Welcome to Macro!\n")
}

if process.isRunningInLambda {
  Lambda.run(app)
}
else {
  app.listen(1337) {
    console.log("server running on http://localhost:1337/")
  }
}

Build the package using swift lambda build -d 5.2 and deploy it to AWS by calling swift lambda deploy -d 5.2. It expects a Lambda configuration called HelloWorld (select a different function using the -f argument).

The -d 5.2 is necessary until AmazonLinux 5.3 development toolchains are available.

A more complex example: express-simple-lambda, it looks like this:

$ swift lambda build -h
Unknown argument: -h

usage: swift lambda build [mode] [options]

Modes:
  -c, --configuration debug|release [default: debug]
  --clean build|dist                [default: build]

Product:
  -p, --product <product>           [default: directory name]
  -d, --destination <dest>

Options:
  -v, --verbose
  -s, --silent
  --static
  --static-libs <libs>

$ swift lambda deploy -h
usage: swift lambda deploy [options]

  -f, --function <name>
  -p, --product  <product>
  -t, --template <SAM template>     (optional)
  --stack-name   <SAM stackname>    (optional)

If no function/product name is provided, the current directory
will be used.

Build Options:
  --skip-build                      (do not invoke swift lambda build)
  -c, --configuration debug|release [default: debug]
  -d, --destination <dest>
  --static
  --static-libs <libs>

Options:
  -v, --verbose
  -s, --silent

• Swift 5.3 required on host (SR-13312)
• There is no "direct" Xcode support yet, i.e. the package needs to be created using a Package.swift (vs create a new tool project in Xcode). We might address that and even provide a SwiftXcode style Lambda Xcode template. Direct deployment from within Xcode should be possible. (Issue 2)
• C++ support seems b0rked right now. Regular C code compile just fine (e.g. SwiftNIO includes some). (SPMDestinations Issue #4)
• swift lambda build has some support for static linking already builtin, but it doesn't fully work yet. To be fixed. (static linking reduces the size of the zip and further improves Lambda startup time). (Issue 3)
• There is no Swift 5.3 toolchain for Amazon Linux yet (just 5.2). (SPMDestinations Issue #5)
• The X toolchains only have the packages that seemed necessary. If someone needs additionals ones please file an issue (the toolchains can carry lots of dev packages, that's perfectly fine).

• Deploying Swift on AWS Lambda
• SPMDestinations
• MacroLambda
• Amazon:
  • AWS Lambda homepage
  • Amazon Web Services API Gateway
• Apple:
  • WWDC 2020: Use Swift on AWS Lambda with Xcode
  • Swift Blog: Introducing Swift AWS Lambda Runtime
  • Swift AWS Lambda Runtime
  • SwiftNIO
• Tutorials by Fabian Fett:
  • Getting started with Swift on AWS Lambda
  • Create your first HTTP endpoint with Swift on AWS Lambda
• Optical Aberration: Messing with Swift AWS Lambda Runtime
  • Part 1
  • Part 2

swift-lambda is brought to you by ZeeZide. We like feedback, GitHub stars, cool contract work, presumably any form of praise you can think of.