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Bootstrap
Client
Context
ExceptionHandling
ThirdParty/Json
Amazon.Lambda.RuntimeSupport.csproj
README.md

README.md

Amazon.Lambda.RuntimeSupport

This package contains classes that can be used to create .NET Core custom runtimes in AWS Lambda. You can learn more about AWS Lambda custom runtimes here.

LambdaBootstrap

The Amazon.Lambda.RuntimeSupport.LambdaBootstrap class handles initialization of the function and runs the loop that receives and handles invocations from the AWS Lambda service. Take a look at the signature of the ToUpperAsync method in the example below. This signature is the default for function handlers when using the Amazon.Lambda.RuntimeSupport.LambdaBootstrap class.

private static MemoryStream ResponseStream = new MemoryStream();
private static JsonSerializer JsonSerializer = new JsonSerializer();

private static async Task Main(string[] args)
{
    using(var bootstrap = new LambdaBootstrap(ToUpperAsync))
    {
        await bootstrap.RunAsync();
    }
}

private static Task<InvocationResponse> ToUpperAsync(InvocationRequest invocation)
{
    var input = JsonSerializer.Deserialize<string>(invocation.InputStream);

    ResponseStream.SetLength(0);
    JsonSerializer.Serialize(input.ToUpper(), ResponseStream);
    ResponseStream.Position = 0;

    return Task.FromResult(new InvocationResponse(responseStream, false));
}

The Amazon.Lambda.RuntimeSupport.HandlerWrapper class allows you to use existing handlers with LambdaBootstrap. The Amazon.Lambda.RuntimeSupport.HandlerWrapper class also takes care of deserialization and serialization for you.

private static async Task Main(string[] args)
{
    using(var handlerWrapper = HandlerWrapper.GetHandlerWrapper((Func<string, ILambdaContext, string>)ToUpper, new JsonSerializer()))
    using(var bootstrap = new LambdaBootstrap(handlerWrapper))
    {
        await bootstrap.RunAsync();
    }
}

// existing handler doesn't conform to the new Amazon.Lambda.RuntimeSupport default signature
public static string ToUpper(string input, ILambdaContext context)
{
    return input?.ToUpper();
}

The Amazon.Lambda.RuntimeSupport.RuntimeApiClient class handles interaction with the AWS Lambda Runtime Interface. This class is meant for advanced use cases. Under most circumstances you won't use it directly.

Below is an excerpt from the Amazon.Lambda.RuntimeSupport.LambdaBootstrap class that demonstrates how Amazon.Lambda.RuntimeSupport.RuntimeApiClient is used. Read the full source for Amazon.Lambda.RuntimeSupport.LambdaBootstrap to learn more.

internal async Task InvokeOnceAsync()
{
    using (var invocation = await Client.GetNextInvocationAsync())
    {
        InvocationResponse response = null;
        bool invokeSucceeded = false;

        try
        {
            response = await _handler(invocation);
            invokeSucceeded = true;
        }
        catch (Exception exception)
        {
            await Client.ReportInvocationErrorAsync(invocation.LambdaContext.AwsRequestId, exception);
        }

        if (invokeSucceeded)
        {
            try
            {
                await Client.SendResponseAsync(invocation.LambdaContext.AwsRequestId, response?.OutputStream);
            }
            finally
            {
                if (response != null && response.DisposeOutputStream)
                {
                    response.OutputStream?.Dispose();
                }
            }
        }
    }
}
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