README.md

Amazon.Lambda.ApplicationLoadBalancerEvents

This package contains classes that can be used as requests and responses for Lambda functions that process Elastic Load Balancing's Application Load Balancers.

Classes

ApplicationLoadBalancerRequest

The ApplicationLoadBalancerRequest class contains information relating to the request coming from an Application Load Balancer.

Multi-Value Headers

ELB Lambda Target Groups can be enabled to support multiple values for headers and querystring parameters. If support is enabled and a client sends a request with multiple values then the MultiValueHeaders and MultiValueQueryStringParameters collections should be used instead of Headers and QueryStringParameters collection.

Either Headers or MultiValueHeaders collection will be set, never both. The Lambda function can check to see which collection has values and then use that collection from then on.

Sample Functions

The following is a sample class and Lambda function that receives an Application Load Balancer request as an input, writes some of the record data to CloudWatch Logs, and responds with a 200 status and the same body as the request. (Note that by default anything written to Console will be logged as CloudWatch Logs events.)

Function handler

public class Function
{
    public ApplicationLoadBalancerResponse Handler(ApplicationLoadBalancerRequest request)
    {
        Console.WriteLine($"Processing request data for request {request.RequestContext.RequestId}.");
        Console.WriteLine($"Body size = {request.Body.Length}.");
        var headerNames = string.Join(", ", request.Headers.Keys);
        Console.WriteLine($"Specified headers = {headerNames}.");

        return new ApplicationLoadBalancerResponse
        {
            Body = request.Body,
            StatusCode = 200,
        };
    }
}