Add Streaming Lambda Examples with API Gateway and Function URL

[sebsto]

Overview

This PR reorganizes and enhances the streaming Lambda examples by splitting them into two distinct examples that demonstrate different invocation methods:

1. Streaming+FunctionUrl - Streaming responses via Lambda Function URLs
2. Streaming+APIGateway - Streaming responses via API Gateway REST API

Changes

🔄 Restructured Examples

• Renamed: Examples/Streaming/ → Examples/Streaming+FunctionUrl/

  • Maintains the original streaming example using Lambda Function URLs
  • Updated documentation to clarify Function URL-specific configuration
  • Improved AWS credentials handling in curl examples

• New: Examples/Streaming+APIGateway/

  • Comprehensive example demonstrating API Gateway REST API with response streaming
  • Complete SAM template with proper IAM roles and streaming configuration
  • Detailed documentation covering API Gateway-specific setup

📚 Documentation Improvements

Streaming+FunctionUrl

• Clarified that this example uses Lambda Function URLs
• Updated curl examples to use eval $(aws configure export-credentials --format env) for cleaner credential handling
• Maintained all existing functionality and deployment instructions

Streaming+APIGateway (New)

• 316-line comprehensive README covering:
  • Response streaming concepts and benefits
  • HTTP status code and header configuration
  • Streaming response body patterns
  • Local testing instructions
  • Complete SAM deployment guide with detailed template explanation
  • API Gateway-specific invocation with AWS Sigv4 authentication
  • Payload format documentation with example JSON
  • Security and reliability best practices
  • How API Gateway streaming works under the hood

🛠️ Technical Details

API Gateway Streaming Configuration

The new example demonstrates:

• Special Lambda URI: /response-streaming-invocations endpoint
• responseTransferMode: STREAM configuration
• IAM role with both lambda:InvokeFunction and lambda:InvokeWithResponseStream permissions
• Proper timeout configuration (60s) to accommodate streaming duration

SAM Template Features

- Lambda function with streaming support (arm64, provided.al2)
- API Gateway REST API with OpenAPI 3.0 definition
- IAM execution role for API Gateway to invoke Lambda with streaming
- Complete outputs for easy testing (API URL and Lambda ARN)

🔐 Security Enhancements

Both examples now include comprehensive security best practices:

• API Gateway access logging
• Throttling configuration
• AWS WAF integration recommendations
• Lambda concurrent execution limits
• Environment variable encryption
• Dead Letter Queue (DLQ) configuration
• VPC configuration guidance

🧪 Testing

Both examples support:

• Local testing: swift run with curl invocation on port 7000
• AWS deployment: Complete SAM templates with deployment instructions
• Authenticated invocation: AWS Sigv4 examples with proper credential handling

Benefits

1. Clearer separation: Developers can now easily choose between Function URLs and API Gateway based on their use case
2. Better documentation: Each example has tailored documentation for its specific invocation method
3. Production-ready: Includes security best practices and proper IAM configuration
4. Easier testing: Improved credential handling in curl examples

Breaking Changes

None - this is purely additive. The original streaming example is preserved as Streaming+FunctionUrl.

Testing Checklist

• Local testing works for both examples
• SAM deployment templates are valid
• Documentation is comprehensive and accurate
• Security best practices are documented
• Curl examples work with proper authentication

Related Documentation

• AWS Lambda Response Streaming
• API Gateway Lambda Proxy Integration with Streaming
• Lambda Function URLs
  EOF