Siemens.AspNet.Lambda.Sdk.Contracts 0.1.0-alpha.99

Siemens.AspNet.Lambda.Sdk.Contracts

The Siemens.AspNet.Lambda.Sdk.Contracts NuGet package provides core abstractions—interfaces, delegates, and base classes—essential for implementing AWS Lambda functions using the Siemens Lambda SDK. This contract library enables consistent, maintainable, and testable Lambda implementations.

📖 Overview

This package defines interfaces and delegates crucial for middleware-based pipeline handling and function execution in AWS Lambda environments.

✅ Key Abstractions

• 📐 Lambda Function Handlers

  • IFunctionHandler<TRequest>
  • IFunctionHandler<TRequest, TResponse>

• 🔗 Middleware Interfaces

  • ILambdaMiddleware<TRequest>
  • ILambdaMiddleware<TRequest, TResponse>

• 🚦 Pipeline Executors

  • ILambdaPipelineExecutor<TRequest>
  • ILambdaPipelineExecutor<TRequest, TResponse>

• 🔀 Delegates for Request Handling

  • LambdaRequestDelegate<TRequest>
  • LambdaRequestDelegate<TRequest, TResponse>

• 📌 Structured Error Logging

  • SpecificErrorLogHandler

📦 Installation

Using the .NET CLI

dotnet add package Siemens.AspNet.Lambda.Sdk.Contracts

🚀 Example Implementations

Implementing a simple Lambda function without response

public class MyFunction : FunctionBase<SQSEvent>
{
    public override Task HandleAsync(SQSEvent request, ILambdaContext context)
    {
        // Your Lambda handling logic here      
    }
}

Implementing a simple Lambda function with request and response

public class Function : FunctionBase<CognitoPostConfirmationEvent, CognitoPostConfirmationEvent>
{
    public override Task<CognitoPostConfirmationEvent> HandleAsync(CognitoPostConfirmationEvent request,
                                                                   ILambdaContext context)
    {
        // Your Lambda handling logic here        
    }
}

Implementing a Lambda function with custom handler and dependency injection

Function:

public class Function : FunctionHandlerBase<Startup, CognitoPostConfirmationEvent, CognitoPostConfirmationEvent>
{
}

Startup:

public sealed class Startup : LambdaStartup
{
    protected override void ConfigureServices(IServiceCollection services,
                                              IConfiguration configuration)
    {
        base.ConfigureServices(services, configuration);

        services.AddFunctionHandler();
    }
}

FunctionHandler:

internal static class AddFunctionHandlerExtension
{
    internal static void AddFunctionHandler(this IServiceCollection services)
    {
        services.AddSingletonIfNotExists<IFunctionHandler<CognitoPostConfirmationEvent, CognitoPostConfirmationEvent>, FunctionHandler>();
    }
}

internal sealed class FunctionHandler(IMyService service,
                                      IJsonSerializer jsonSerializer) : IFunctionHandler<CognitoPostConfirmationEvent, CognitoPostConfirmationEvent>
{
    public Task<CognitoPostConfirmationEvent> HandleAsync(CognitoPostConfirmationEvent request,
                                                          ILambdaContext context)
    {
        // Your custom logic here
    }
}

Lambda Middleware Pipeline

Leverage middleware for clean and maintainable request handling. Sample middleware for error logging: (This middleware is already included in the SDK and active !)

internal static class AddErrorLogRequestMiddlewareExtension
{
    internal static void AddErrorLogRequestMiddleware(this IServiceCollection services)
    {
        services.AddErrorLoggingStrategyForLambda();
            
        services.AddSingleton(typeof(ILambdaMiddleware<>), typeof(ErrorLogRequestMiddleware<>));
    }
}

internal sealed class ErrorLogRequestMiddleware<TRequest>(IErrorLoggingStrategyForLambda errorLoggingStrategy) : ILambdaMiddleware<TRequest>
{
    public async Task InvokeAsync(TRequest request,
                                    ILambdaContext context,
                                    LambdaRequestDelegate<TRequest> requestDelegate)
    {
        try
        {
            await requestDelegate(request, context).ConfigureAwait(false);
        }
        catch (Exception e)
        {
            await errorLoggingStrategy.HandleAsync(context, e).ConfigureAwait(false);
            throw;
        }
    }
}

📌 Usage & Best Practices

• Use provided interfaces to structure Lambda functions clearly.
• Middleware helps implement cross-cutting concerns (logging, validation, error handling).
• Implement custom pipeline executors for advanced control over middleware execution flow.

📚 Documentation

Detailed documentation and examples are included in the source repository and will be published online soon.

📢 Contributing

Contributions and feedback are highly appreciated! Feel free to create issues or submit pull requests.