Integration with AWS Lambda functions

Document updated on Jun 9, 2022

The Lambda integration allows you to invoke Amazon Lambda functions on a KrakenD endpoint call. The content returned by the lambda function can be treated and manipulated as any other backend.

The payload that is sent to the Lambda function comes from the request and depends on the method used by the endpoint:

• Method GET: The payload contains all the request parameters.
• Non-GET methods: The payload is defined by the content of the body in the request.

You don’t need to set an Amazon API Gateway in the middle as KrakenD does this job for you.

Lambda configuration

The inclusion requires you to add the code in the extra_config of your backend section, using the backend/lambda namespace.

The supported parameters are:

• function_name: Name of the lambda function as saved in the AWS service.
• function_param_name: The endpoint {placeholder} that sets the function name. You have to choose between function_name and function_param_name but not both.
• region: The AWS identifier region (e.g.: us-east-1, eu-west-2, etc. )
• max_retries: Maximum times you want to execute the function until you have a successful response.
• endpoint: An optional parameter to customize the Lambda endpoint to call. Useful when Localstack is used for testing.

Authentication and connectivity

The KrakenD machine needs to have connectivity with your AWS account and have the credentials to do so. There are several ways you can achieve this:

• By copying your AWS credentials in the default file, ~/.aws/credentials (and maybe an additional ~/.aws/config and the env var AWS_PROFILE if you have several profiles)
• By passing the environment variables with at least AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY (and maybe AWS_REGION) when starting KrakenD.
• By having an IAM user with a policy and execution role that let you invoke the function from the machine

When setting the credentials, ensure the Lambda is callable within the KrakenD box with the selected method.

If your machine has the AWS CLI installed, you can test your Lambda:

$aws lambda invoke --region us-east-1 --function-name myLambdaFunction --output json result.json

Authentication examples

Mounting an existing .aws directory with the credentials in it (notice that the home of the Docker user is krakend):

$docker run --rm -it -p "8080:8080" \
    -e "AWS_PROFILE=default" \
    -v "/home/user/.aws:/home/krakend/.aws:ro" \
    -v "$PWD:/etc/krakend" krakend/krakend-ee:2.2

Passing the credentials directly:

$docker run --rm -it -p "8080:8080" \
    -e "AWS_ACCESS_KEY_ID=XXX" \
    -e "AWS_SECRET_ACCESS_KEY=XXX" \
    -e "AWS_REGION=eu-west-1" \
    -v "$PWD:/etc/krakend" krakend/krakend-ee:2.2

Example: Associate a lambda to a backend

When you associate a KrakenD endpoint to a unique lambda function, use this configuration:

{
  "endpoint": "/call-a-lambda",
  "backend": [
    {
      "host": ["ignore"],
      "url_pattern": "/ignore",
      "extra_config": {
        "backend/lambda": {
          "function_name": "myLambdaFunction",
          "region": "us-east-1",
          "max_retries": 1
        }
      }
    }
  ]
}

Here is an example of Lambda code that could run a Hello World (NodeJS):

exports.handler = async (event) => {
    // TODO implement
    const response = {
        statusCode: 200,
        body: {"message": "Hello World"},

    };
    return response;
};

Example: Take the lambda from the URL

When the name of the Lambda depends on a parameter passed in the endpoint, use this configuration instead:

{
  "endpoint": "/call-a-lambda/{lambda}",
  "backend": [
    {
      "host": ["ignore"],
      "url_pattern": "/ignore",
      "extra_config": {
        "backend/lambda": {
          "function_param_name": "Lambda",
          "region": "us-west1",
          "max_retries": 1
        }
      }
    }
  ]
}

In this example, the function_param_name tells us which is the placeholder in the endpoint setting the Lambda. In this case, {lambda}.

Following the code, a call GET /call-a-lambda/my-lambda would produce a call to the My-lambda function in AWS.