2.0.0

The AWS Lambda Runtime for Swift v2 is now officially available.

Overview

Swift AWS Lambda Runtime v2 introduces a complete redesign of the API with async/await-first architecture, response streaming support, background task execution, and seamless integration with Swift Service Lifecycle. This release prioritizes developer experience, and structured concurrency.

🚀 v2 - Major New Features

Complete Swift 6 Concurrency Integration

• Full async/await support throughout the entire API surface
• Structured concurrency with proper task management and cancellation
• Swift 6 compatibility with complete concurrency checking
• Non-blocking I/O foundation built on SwiftNIO for optimal performance
• Own the main() function for complete control over initialization

// Clean async/await API 
let runtime = LambdaRuntime { (event: Input, context: LambdaContext) async throws -> Output in
    let result = try await someAsyncOperation()
    return Output(data: result)
}

try await runtime.run()

Response Streaming Support

• Stream large responses incrementally to improve time-to-first-byte (TTFB) performance
• 200MB soft limit for streamed responses vs 6MB for buffered responses
• Reduced memory usage for large responses
• Support for custom HTTP status codes and headers in the streamed response

let runtime = LambdaRuntime { (event: StreamingRequest, responseWriter, context: LambdaContext) in
    for i in 1...10 {
        try await responseWriter.write(ByteBuffer(string: "Message \(i)\n"))
        try await Task.sleep(for: .milliseconds(500))
    }
    try await responseWriter.finish()
}

Background Task Execution

• Execute code after returning response without affecting response latency
• Structured concurrency approach following Swift best practices

let runtime = LambdaRuntime { (event: Input, outputWriter: some LambdaResponseWriter<Output>, context: LambdaContext) in
    // Return response immediately
    try await output.write(Greeting(message: event.message))
    
    // Execute background work
    try await performAnalytics(event)
    try await updateCache()
}

Swift Service Lifecycle Integration

• Structured dependency with ServiceGroup
• Graceful shutdown handling with proper resource cleanup
• Eliminate LambdaTerminator complexity

let postgresClient = PostgresClient()
let runtime = LambdaRuntime { (event: Input, context: LambdaContext) in
    try await postgresClient.query("SELECT * FROM users")
}

let serviceGroup = ServiceGroup(
    services: [postgresClient, runtime],
    configuration: .init(gracefulShutdownSignals: [.sigterm])
)
try await serviceGroup.run()

Changes between 2.0.0-beta.1 and 2.0.0

What's Changed

SemVer Major

• Use a struct for ClientContext (fix #169) by @sebsto in #539
• Remove dependency on DispatchWallTime (fix #384) by @sebsto in #540
• Revert streaming codable handler and provide it as an example, not an API by @sebsto in #549
• [fix] The library must compile when no traits are enabled by @sebsto in #563

SemVer Minor

• Performance Test the invocation loop (fix #377) by @sebsto in #542
• Add hummingbird Lambda example by @sebsto in #544
• Propagate Connection Closed Information up to top-level (fix #465) by @sebsto in #545
• add support for LOCAL_LAMBDA_PORT by @sebsto in #557
• Bump Amazon RDS version 19 PG 17 by @sebsto in #561
• Update toolchain and doc for 6.2 by @sebsto in #564
• Apply recommendation for security and reliability by @sebsto in #573

SemVer Patch

• fix: Fix deadline header with correct instant value (#551) by @sebsto in #552
• Split LambdaRuntimeClient in two files for easier reading by @sebsto in #554
• Rename Tests' timeout() function by @sebsto in #555
• refactor the Swift Settings in Package.swift by @sebsto in #558
• Allow compiling on macOS by @fabianfett in #559
• [Example] Use smaller containers in all examples by @sebsto in #571
• [Example] Add APIGatewayV1 example by @everyplace in #569
• Rename APIGateway example to APIGatewayV2 by @sebsto in #575

Other Changes

• Fix link (Response Streaming) in readme.md by @natanrolnik in #543
• [doc] Updated streaming response limit to 200 MB by @dsplatonov in #548

New Contributors

• @natanrolnik made their first contribution in #543
• @dsplatonov made their first contribution in #548
• @everyplace made their first contribution in #569

Full Changelog: 2.0.0-beta.1...2.0.0