#AWS Lambda Handler

The AWS Lambda handler is used to send requests to AWS Lambda. This handler can be used as an alternative to AWS API Gateway when exposing Lambda functions as an API or HTTP endpoint.

Note: Many customers use Zuplo's AWS Lamdba handler as a replacement for using AWS API Gateway, however it should not be considered a complete fire-and-forget replacement. Some features, such as the way certain errors are handled may differ. We recommend testing your API to ensure the behavior is as you expect, especially in migration scenarios.

#IAM Permissions

Zuplo will need to be granted access to execute your Lambda function. It is recommended you create an IAM user and grant that account only the permission needed to invoke the lambda function. The IAM use does not require console access, only API access. The IAM user used by Zuplo requires the [AWSLambdaRole[(https://docs.aws.amazon.com/lambda/latest/dg/access-control-identity-based.html)] role. This role can be scoped to only the specific Lambda functions required.

#Setup via Portal

To setup the AWS Lambda handler in the portal UI, select the AWS Lambda handler on any route.

Configure the properties for your AWS Lambda function.

#Setup via routes.oas.json

The AWS Lambda handler can be setup by editing the routes.oas.json file directly by configuring the handler property on any route's x-zuplo-route property.

{
  "handler": {
    "export": "awsLambdaHandler",
    "module": "$import(@zuplo/runtime)",
    "options": {
      "accessKeyId": "$env(AWS_ACCESS_KEY_ID)",
      "functionName": "demo-post-1",
      "region": "us-east-2",
      "secretAccessKey": "$env(AWS_SECURE_ACCESS_KEY)"
    }
  }
}

#Binary Media Types

For content types, the binaryMediaTypes option allows specifying which content types get converted to base64 encoded strings when sent as the body to the AWS Lambda function. See AWS docs for details.

{
  "handler": {
    "export": "awsLambdaHandler",
    "module": "$import(@zuplo/runtime)",
    "options": {
      "accessKeyId": "$env(AWS_ACCESS_KEY_ID)",
      "functionName": "demo-post-1",
      "region": "us-east-2",
      "secretAccessKey": "$env(AWS_SECURE_ACCESS_KEY)",
      "binaryMediaTypes": ["image/png", "application/pdf"]
    }
  }
}

#X-Amzn-Trace-Id Header

For the purposes of troubleshooting and tracing, it can be useful to return the X-Amzn-Trace-Id header in the response. This can help correlate AWS Lambda events or errors with Zuplo requests/responses. This header is disabled by default, but it can be enabled by setting the configuration option returnAmazonTraceIdHeader to true.

{
  "handler": {
    "export": "awsLambdaHandler",
    "module": "$import(@zuplo/runtime)",
    "options": {
      "accessKeyId": "$env(AWS_ACCESS_KEY_ID)",
      "functionName": "demo-post-1",
      "region": "us-east-2",
      "secretAccessKey": "$env(AWS_SECURE_ACCESS_KEY)",
      "returnAmazonTraceIdHeader": true
    }
  }
}

#Compressed Body Content

The Zuplo handler supports gzip and deflate compression of the content of the AWS Lambda response body property. In order to instruct the Zuplo handler to decompress the body content add a property on the outgoing event called bodyEncoding and set the value to gzip or deflate.

The response event would look like this:

{
  "isBase64Encoded": true,
  "bodyEncoding": "gzip",
  "body": "COMPRESSSED AND BASE64 ENCODED BODY",
  "...": "other properties..."
}

#API Gateway Compatibility

The AWS Lambda handler can also call Lambda functions that were built for API Gateway.

Setting options.useLambdaProxyIntegration to true will tell the handler to call the function with the event format that matches with AWS API Gateway. You can also choose between the payload format by setting options.payloadFormatVersion to either 1.0 or 2.0.

The value for requestContext.resourcePath sent to the AWS Lambda function is the parameterized path of the route. Zuplo uses path-to-regex style paths (i.e. /my/route/:param1) instead of OpenAPI style paths (i.e. /my/route/{param1}) for routes. By default, the value of resourcePath is the Zuplo route value. Setting useAwsResourcePathStyle to true will convert the value to the AWS format.

For more details about the AWS payload formats see AWS's documentation.

Below is an example lambda handler configured for proxy integration with payload format 2.0.

{
  "handler": {
    "export": "awsLambdaHandler",
    "module": "$import(@zuplo/runtime)",
    "options": {
      "accessKeyId": "$env(AWS_ACCESS_KEY_ID)",
      "functionName": "demo-post-1",
      "region": "us-east-2",
      "secretAccessKey": "$env(AWS_SECURE_ACCESS_KEY)",
      "useLambdaProxyIntegration": true,
      "payloadFormatVersion": "2.0",
      "useAwsResourcePathStyle": true
    }
  }
}