Add support for Lambda Managed Instances without changing the public API

[sebsto]

AWS launched Lambda Managed Instance, i.e Lambda functions running on EC2 instances.

This comes with a major change in the programming model as function handlers are now allowed to run concurrently on the same machine (multiple in flight events being processed in parallel in the same execution environment). The maximum concurrency per runtime environment is controlled by the user.

This PR adds support for running multiple Runtime Interface Clients (RICs) concurrently when deployed on Lambda Managed Instances, enabling the runtime to handle multiple invocations simultaneously within a single execution environment.

This PR is a followup to #617 which used another approach to support Lambda Managed Instances by changing the public API and requiring that all handlers must conform to Sendable. The original PR was closed as we agreed that only a fraction of the Lambda functions will be deployed on EC2 and it was not worth adding a Sendable requirement for all.

Changes

• Introduced thread-safe LambdaManagedRuntime: Created new Sendable-conforming runtime class that supports concurrent handler execution with atomic guards to prevent multiple runtime instances and thread-safe handler requirements (Handler: StreamingLambdaHandler & Sendable)

• Added Sendable adapter types: Implemented LambdaHandlerAdapterSendable, LambdaCodableAdapterSendable, LambdaJSONEventDecoderSendable, and LambdaJSONOutputEncoderSendable - all thread-safe versions of existing adapters that enforce Sendable conformance for concurrent execution environments

• Enhanced handler protocols for concurrency: Extended handler protocols to support Sendable constraints and concurrent response writing through LambdaResponseStreamWriter & Sendable, enabling safe multi-threaded invocation processing

• Implemented ServiceLifecycle integration: Added managed runtime support for structured concurrency lifecycle management, allowing proper startup/shutdown coordination in multi-concurrent environments

• Created comprehensive Lambda Managed Instances examples: Built three demonstration functions showcasing concurrent execution capabilities, streaming responses, and background processing patterns specific to the new managed instances deployment model

Context
Lambda Managed Instances support multi-concurrent invocations where multiple invocations execute simultaneously within the same execution environment. The runtime now detects the configured concurrency level and launches the appropriate number of RICs to handle concurrent requests efficiently.

When AWS_LAMBDA_MAX_CONCURRENCY is 1 or unset, the runtime maintains the existing single-threaded behaviour for optimal performance on traditional Lambda deployments.

[Copilot]

Pull request overview

This pull request adds support for Lambda Managed Instances, enabling Swift Lambda functions to handle multiple concurrent invocations within a single execution environment. The implementation introduces thread-safe runtime components with Sendable conformance while maintaining backward compatibility with the existing single-threaded Lambda runtime.

Key Changes:

• Introduced LambdaManagedRuntime class with thread-safe handler execution supporting concurrent invocations based on the AWS_LAMBDA_MAX_CONCURRENCY environment variable
• Created Sendable-conforming adapter types (LambdaHandlerAdapterSendable, LambdaCodableAdapterSendable, LambdaJSONEventDecoderSendable, LambdaJSONOutputEncoderSendable) to ensure safe concurrent execution
• Refactored LambdaRuntime to extract reusable methods (startRuntimeInterfaceClient, startLocalServer) shared with LambdaManagedRuntime

Reviewed changes

Copilot reviewed 23 out of 23 changed files in this pull request and generated 7 comments.

Show a summary per file

File	Description
scripts/extract_aws_credentials.sh	Removed script (likely no longer needed)
Tests/AWSLambdaRuntimeTests/Utils.swift	Added test helper for creating LambdaContext instances
Tests/AWSLambdaRuntimeTests/LambdaManagedRuntimeTests.swift	Comprehensive tests for concurrent handler execution, Sendable constraints, and thread-safe adapters
Sources/AWSLambdaRuntime/Runtime/LambdaRuntime.swift	Refactored to extract reusable methods and renamed atomic guard variable for clarity
Sources/AWSLambdaRuntime/Runtime/LambdaRuntime+Codable.swift	Added Sendable conformance to VoidEncoder
Sources/AWSLambdaRuntime/ManagedRuntime/LambdaManagedRuntimeHandlers.swift	Introduced ClosureHandlerSendable for thread-safe closure-based handlers
Sources/AWSLambdaRuntime/ManagedRuntime/LambdaManagedRuntime.swift	Core implementation of managed runtime with concurrency detection and multiple RIC support
Sources/AWSLambdaRuntime/ManagedRuntime/LambdaManagedRuntime+ServiceLifecycle.swift	ServiceLifecycle integration for managed runtime
Sources/AWSLambdaRuntime/ManagedRuntime/LambdaManagedRuntime+Codable.swift	Thread-safe adapter implementations for managed runtime
Sources/AWSLambdaRuntime/FoundationSupport/LambdaRuntime+JSON.swift	Convenience initializers for LambdaRuntime with JSON encoding/decoding
Sources/AWSLambdaRuntime/FoundationSupport/LambdaManagedRuntime+JSON.swift	Sendable JSON encoder/decoder implementations and convenience initializers for managed runtime
Sources/AWSLambdaRuntime/FoundationSupport/LambdaHandler+JSON.swift	Extracted common JSON handler support to separate file
[email protected]	Added ManagedRuntimeSupport trait and updated dependency versions
Package.swift	Added ManagedRuntimeSupport trait to default enabled traits and updated dependency versions
Examples/Streaming+Codable/Tests/LambdaStreamingCodableTests.swift	Updated logger label for consistency
Examples/ManagedInstances/template.yaml	SAM template for deploying managed instances examples
Examples/ManagedInstances/Sources/Streaming/main.swift	Streaming response example for managed instances
Examples/ManagedInstances/Sources/HelloJSON/main.swift	Simple JSON request/response example for managed instances
Examples/ManagedInstances/Sources/BackgroundTasks/main.swift	Background processing example for managed instances
Examples/ManagedInstances/README.md	Documentation for deploying and testing managed instances examples
Examples/ManagedInstances/Package.swift	Package definition for managed instances examples
Examples/ManagedInstances/.gitignore	Ignore patterns for managed instances examples
.github/workflows/pull_request.yml	Added ManagedInstances to CI examples list

Comments suppressed due to low confidence (3)

Sources/AWSLambdaRuntime/FoundationSupport/LambdaManagedRuntime+JSON.swift:149

• Inconsistent default logger label. This initializer uses "LambdaRuntime" as the default logger label, but the previous initializer on line 122 uses "LambdaManagedRuntime". For consistency, this should likely also use "LambdaManagedRuntime" since it's an extension on LambdaManagedRuntime.
  Sources/AWSLambdaRuntime/FoundationSupport/LambdaManagedRuntime+JSON.swift:207
• Inconsistent default logger label. This initializer uses "LambdaRuntime" as the default logger label, but line 122 uses "LambdaManagedRuntime". For consistency across the LambdaManagedRuntime extension, this should likely also use "LambdaManagedRuntime".
  Sources/AWSLambdaRuntime/FoundationSupport/LambdaManagedRuntime+JSON.swift:176
• Inconsistent default logger label. This initializer uses "LambdaRuntime" as the default logger label, but line 122 uses "LambdaManagedRuntime". For consistency across the LambdaManagedRuntime extension, this should likely also use "LambdaManagedRuntime".

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