initial version of a custom Swift Runtime for AWS Lambda

Author: tonisuter

.gitignore

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-# Xcode
-#
-# gitignore contributors: remember to update Global/Xcode.gitignore, Objective-C.gitignore & Swift.gitignore
-
-## Build generated
-build/
-DerivedData/
-
-## Various settings
-*.pbxuser
-!default.pbxuser
-*.mode1v3
-!default.mode1v3
-*.mode2v3
-!default.mode2v3
-*.perspectivev3
-!default.perspectivev3
-xcuserdata/
-
-## Other
-*.moved-aside
-*.xccheckout
-*.xcscmblueprint
-
-## Obj-C/Swift specific
-*.hmap
-*.ipa
-*.dSYM.zip
-*.dSYM
-
-## Playgrounds
-timeline.xctimeline
-playground.xcworkspace
-
-# Swift Package Manager
-#
-# Add this line if you want to avoid checking in source code from Swift Package Manager dependencies.
-# Packages/
-# Package.pins
-# Package.resolved
-.build/
-
-# CocoaPods
-#
-# We recommend against adding the Pods directory to your .gitignore. However
-# you should judge for yourself, the pros and cons are mentioned at:
-# https://guides.cocoapods.org/using/using-cocoapods.html#should-i-check-the-pods-directory-into-source-control
-#
-# Pods/
-
-# Carthage
-#
-# Add this line if you want to avoid checking in source code from Carthage dependencies.
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-Carthage/Build
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-# It is recommended to not store the screenshots in the git repo. Instead, use fastlane to re-generate the
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-fastlane/report.xml
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-fastlane/test_output
+.DS_Store
+.build_linux
+lambda.zip

AWSLambdaSwift/.gitignore

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+.DS_Store
+/.build
+/Packages
+/*.xcodeproj

AWSLambdaSwift/Package.swift

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+// swift-tools-version:4.2
+
+import PackageDescription
+
+let package = Package(
+    name: "AWSLambdaSwift",
+    products: [
+        .library(
+            name: "AWSLambdaSwift",
+            targets: ["AWSLambdaSwift"]),
+    ],
+    dependencies: [],
+    targets: [
+        .target(
+            name: "AWSLambdaSwift",
+            dependencies: []),
+    ]
+)

AWSLambdaSwift/README.md

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+# AWSLambdaSwift
+
+A description of this package.

AWSLambdaSwift/Sources/AWSLambdaSwift/Runtime.swift

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+import Foundation
+
+func log(_ object: Any, flush: Bool = false) {
+    fputs("\(object)\n", stderr)
+    if flush {
+        fflush(stderr)
+    }
+}
+
+public typealias JSONDictionary = [String: Any]
+
+public class Runtime {
+    var counter = 0
+    let urlSession: URLSession
+    let awsLambdaRuntimeAPI: String
+    let handler: String
+    var lambdas: [String: (JSONDictionary) -> JSONDictionary]
+    
+    public init() throws {
+        self.urlSession = URLSession.shared
+        self.lambdas = [:]
+        
+        let environment = ProcessInfo.processInfo.environment
+        guard let awsLambdaRuntimeAPI = environment["AWS_LAMBDA_RUNTIME_API"],
+           let handler = environment["_HANDLER"] else {
+              throw RuntimeError.missingEnvironmentVariables
+        }
+        
+        self.awsLambdaRuntimeAPI = awsLambdaRuntimeAPI
+        self.handler = handler
+    }
+    
+    func getNextInvocation() throws -> (input: JSONDictionary, requestId: String) {
+        let getNextInvocationEndpoint = URL(string: "http://\(awsLambdaRuntimeAPI)/2018-06-01/runtime/invocation/next")!
+        let (optData, optResponse, optError) = urlSession.synchronousDataTask(with: getNextInvocationEndpoint)
+        
+        guard optError == nil else {
+            throw RuntimeError.endpointError(optError!.localizedDescription)
+        }
+        
+        guard let data = optData else {
+            throw RuntimeError.missingData
+        }
+        
+        guard let jsonObject = try? JSONSerialization.jsonObject(with: data),
+              let input = jsonObject as? JSONDictionary else {
+            throw RuntimeError.invalidData
+        }
+        
+        let httpResponse = optResponse as! HTTPURLResponse
+        let requestId = httpResponse.allHeaderFields["Lambda-Runtime-Aws-Request-Id"] as! String
+        return (input: input, requestId: requestId)
+    }
+    
+    func postInvocationResponse(for requestId: String, response: JSONDictionary) throws {
+        let postInvocationResponseEndpoint = URL(string: "http://\(awsLambdaRuntimeAPI)/2018-06-01/runtime/invocation/\(requestId)/response")!
+        guard let httpBody = try? JSONSerialization.data(withJSONObject: response) else {
+            throw RuntimeError.invalidData
+        }
+        
+        var urlRequest = URLRequest(url: postInvocationResponseEndpoint)
+        urlRequest.httpMethod = "POST"
+        urlRequest.httpBody = httpBody
+        
+        _ = urlSession.synchronousDataTask(with: urlRequest)
+    }
+
+    public func registerLambda(_ name: String, handler: @escaping (JSONDictionary) -> JSONDictionary) {
+        lambdas[name] = handler
+    }
+    
+    public func start() throws {
+        while true {
+            let (input, requestId) = try getNextInvocation()
+            counter += 1
+            log("Invocation-Counter: \(counter)")
+
+            let lambda = lambdas["lambda"]!
+            let output = lambda(input)
+            try postInvocationResponse(for: requestId, response: output)
+        }
+    }
+}

AWSLambdaSwift/Sources/AWSLambdaSwift/RuntimeError.swift

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+enum RuntimeError: Error {
+    case missingEnvironmentVariables
+    case endpointError(String)
+    case missingData
+    case invalidData
+}

AWSLambdaSwift/Sources/AWSLambdaSwift/URLSession+Utils.swift

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+import Foundation
+
+extension URLSession {
+    func synchronousDataTask(with url: URL) -> (Data?, URLResponse?, Error?) {
+        let urlRequest = URLRequest(url: url)
+        return synchronousDataTask(with: urlRequest)
+    }
+    
+    func synchronousDataTask(with urlRequest: URLRequest) -> (Data?, URLResponse?, Error?) {
+        var data: Data?
+        var response: URLResponse?
+        var error: Error?
+        
+        let semaphore = DispatchSemaphore(value: 0)
+        
+        let dataTask = self.dataTask(with: urlRequest) {
+            data = $0
+            response = $1
+            error = $2
+
+            semaphore.signal()
+        }
+        dataTask.resume()
+
+        _ = semaphore.wait(timeout: .distantFuture)
+        return (data, response, error)
+    }
+}

ExampleLambda/.gitignore

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+.DS_Store
+/.build
+/Packages
+/*.xcodeproj

ExampleLambda/Package.resolved

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+{
+  "object": {
+    "pins": [
+
+    ]
+  },
+  "version": 1
+}

ExampleLambda/Package.swift

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+// swift-tools-version:4.2
+
+import PackageDescription
+
+let package = Package(
+    name: "ExampleLambda",
+    dependencies: [
+        .package(path: "../AWSLambdaSwift")
+    ],
+    targets: [
+        .target(
+            name: "ExampleLambda",
+            dependencies: ["AWSLambdaSwift"]),
+    ]
+)

ExampleLambda/README.md

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+# ExampleLambda
+
+A description of this package.

ExampleLambda/Sources/ExampleLambda/main.swift

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+import AWSLambdaSwift
+
+func lambda(input: JSONDictionary) -> JSONDictionary {
+    print(input)
+    return ["hello": "world", "number": 42, "strings": ["one", "two", "three"]]
+}
+
+let runtime = try Runtime()
+runtime.registerLambda("lambda", handler: lambda)
+try runtime.start()

Makefile

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+EXECUTABLE=ExampleLambda
+PROJECT_PATH=ExampleLambda
+LAMBDA_ZIP=lambda.zip
+
+clean:
+	rm $(LAMBDA_ZIP) || true
+	rm -r $(PROJECT_PATH)/.build_linux || true
+
+build:
+	docker run \
+			--rm \
+			--volume "$(shell pwd)/:/src" \
+			--workdir "/src/$(PROJECT_PATH)" \
+			swift \
+			swift build --build-path ./.build_linux
+
+package_lambda: clean build
+	zip -r -j $(LAMBDA_ZIP) bootstrap $(PROJECT_PATH)/.build_linux/debug/$(EXECUTABLE)

bootstrap

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+#!/bin/sh
+/opt/swift-shared-libs/ld-linux-x86-64.so.2 --library-path /opt/swift-shared-libs/lib ./ExampleLambda