SWIFT-1536 Add AWS Lambda Example (#771)

Author: isabelatkinson

Examples/AWSLambdaExample/Dockerfile

@@ -0,0 +1,2 @@
+FROM swift:5.6-amazonlinux2
+RUN yum -y install cmake openssl-devel cyrus-sasl-devel

Examples/AWSLambdaExample/Package.swift

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+// swift-tools-version:5.5
+// The swift-tools-version declares the minimum version of Swift required to build this package.
+
+import PackageDescription
+
+let package = Package(
+    name: "AWSLambdaExample",
+    platforms: [.macOS(.v12)],
+    dependencies: [
+        .package(
+            url: "https://github.com/swift-server/swift-aws-lambda-runtime.git",
+            branch: "main"
+        ),
+        .package(
+            url: "https://github.com/mongodb/mongo-swift-driver",
+            .upToNextMajor(from: "1.0.0")
+        )
+    ],
+    targets: [
+        .executableTarget(
+            name: "AWSLambdaExample",
+            dependencies: [
+                .product(name: "AWSLambdaRuntime", package: "swift-aws-lambda-runtime"),
+                .product(name: "MongoSwift", package: "mongo-swift-driver")
+            ]
+        ),
+    ]
+)

Examples/AWSLambdaExample/README.md

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+# AWSLambdaExample
+
+This is a minimal working example of using the driver in AWS Lambda. 
+
+## Building the example
+The example code needs to be compiled for Amazon Linux 2 to be run in AWS Lambda.
+You can use [Docker](https://docs.docker.com/desktop/) to achieve this.
+
+First, run the following command to build a Docker image using the [`Dockerfile`](Dockerfile) in
+this directory:
+```
+docker build -t swift-lambda .
+```
+This will install the dependencies necessary to build the driver on Linux.
+
+Note that the `Dockerfile` uses Swift 5.6, the latest version at the time of writing. If you'd like
+to use a different version, visit [DockerHub](https://hub.docker.com/_/swift) for a full list of
+Swift Docker images.
+
+Next, use the image you created to compile the example:
+```
+$ docker run \
+    --rm \
+    --volume "$(pwd)/:/src" \
+    --workdir "/src/" \
+    swift-lambda \
+    swift build --product AWSLambdaExample -c release -Xswiftc -static-stdlib
+```
+
+Finally, run the [`package.sh`](package.sh) script in this directory to create a symlink called
+`bootstrap` and zip the folder:
+```
+./package.sh AWSLambdaExample
+```
+Navigate to the Code section on the page for your AWS Lambda function in the AWS Console and upload
+the `lambda.zip` file created.
+
+## Acknowledgements
+The instructions for using Docker to build the example were largely taken from
+[this blog post](https://fabianfett.dev/getting-started-with-swift-aws-lambda-runtime) by
+Fabian Fett. Feel free to read through the post for more detailed information on the Docker
+commands used.
+
+The `package.sh` script is copied from
+[this example](https://github.com/swift-server/swift-aws-lambda-runtime/blob/main/Examples/Deployment/scripts/package.sh)
+in the `swift-aws-lambda-runtime` repository.

Examples/AWSLambdaExample/Sources/AWSLambdaExample/MongoHandler.swift

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+// begin lambda connection example 1
+import AWSLambdaRuntime
+import Foundation
+import MongoSwift
+import NIO
+
+struct Input: Codable {
+    let number: Double
+}
+
+struct Response: Codable {
+    let ok: Double
+}
+
+@main
+final class MongoHandler: LambdaHandler {
+    typealias Event = Input
+    typealias Output = Response
+
+    let elg: EventLoopGroup
+    let mongoClient: MongoClient
+
+    required init(context _: LambdaInitializationContext) async throws {
+        let uri = ProcessInfo.processInfo.environment["MONGODB_URI"] ?? "mongodb://localhost:27017"
+        self.elg = MultiThreadedEventLoopGroup(numberOfThreads: 4)
+        self.mongoClient = try MongoClient(uri, using: self.elg)
+    }
+
+    deinit {
+        // clean up driver resources
+        try? mongoClient.syncClose()
+        cleanupMongoSwift()
+
+        // shut down EventLoopGroup
+        try? elg.syncShutdownGracefully()
+    }
+
+    func handle(_: Event, context _: LambdaContext) async throws -> Output {
+        let db = self.mongoClient.db("db")
+        let response = try await db.runCommand(["ping": 1])
+        return try BSONDecoder().decode(Output.self, from: response)
+    }
+}
+
+// end lambda connection example 1

Examples/AWSLambdaExample/package.sh

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+#!/bin/bash
+
+set -eu
+
+executable=$1
+
+target=.build/lambda/$executable
+rm -rf "$target"
+mkdir -p "$target"
+cp ".build/release/$executable" "$target/"
+cd "$target"
+ln -s "$executable" "bootstrap"
+zip --symlinks lambda.zip *

etc/build-examples.sh

@@ -2,7 +2,7 @@
 
 exit_code=0
 
-examples=("BugReport" "Docs" "KituraExample" "PerfectExample" "VaporExample" "Atlas")
+examples=("BugReport" "Docs" "KituraExample" "PerfectExample" "VaporExample" "Atlas" "AWSLambdaExample")
 
 branch=${1}
 # Ensure branch is non-empty