AWS Lambda Function URL Emulator

A lightweight Docker image to emulate AWS Lambda Function URLs locally. It works with AWS Lambda Runtime Interface Emulator (RIE) to replicate the behavior of Function URLs for local development and testing.

Features

• Emulates AWS Lambda Function URLs locally.
• Automatically forwards HTTP requests to a locally running Lambda function to work with the AWS Lambda Runtime Interface Emulator.
• Supports APIGatewayProxyEventV2 for HTTP API requests.
• Handles isBase64Encoded for binary data.
• Supports enabling CORS via an environment variable, allowing cross-origin requests.

Getting Started

Run with Docker (Standalone)

Please ensure that RIE is running in a separate container beforehand.

docker run --rm -p 8080:8080 \
  -e RIE_ENDPOINT=http://host.docker.internal:9000/2015-03-31/functions/function/invocations \
  daido1976/aws-lambda-function-url-emulator:latest

The emulator will be available at http://localhost:8080 and forwards requests to the RIE endpoint.

Run with Docker Compose

For a practical example of integrating this emulator with RIE using Docker Compose, refer to the example directory.

Run as a CLI Tool (Go)

Install the emulator as a CLI tool:

go install github.com/daido1976/aws-lambda-function-url-emulator@latest

Run it with:

aws-lambda-function-url-emulator

The emulator will be available at http://localhost:8080 and forwards requests to the default RIE endpoint. To use a custom endpoint, set the RIE_ENDPOINT environment variable:

RIE_ENDPOINT=http://custom-host:9000/2015-03-31/functions/function/invocations aws-lambda-function-url-emulator

Environment Variables

Variable	Description	Default Value
RIE_ENDPOINT	URL for the Lambda Runtime Interface Emulator (RIE)	http://localhost:9000/2015-03-31/functions/function/invocations
ENABLE_CORS	Set this to true to enable CORS for all origins, methods, and headers. Warning: Please be aware that this options may have security implications.	false

License

This project is licensed under the MIT License. See the LICENSE file for details.