Local Development - AWS Lambda RIE

Pre-requisites

• Docker
• docker-compose
• AWS CLI - optional
• Curl/Postman or any other HTTP client

Many times, I was required to test or create AWS Lambda services. I was looking for a solution that would help me do this in a efficient way. I found the AWS Lambda Runtime Interface Emulator (RIE), which is a tool that you can use to test Lambda functions locally. It is a small web server that exposes the Lambda runtime HTTP server via a REST API.

I’ve found the combination of AWS Lambda RIE, Docker, and watchexec to be incredibly powerful For more information about watchexec, you can visit the project’s github page at https://github.com/watchexec/watchexec

As a part of this post, I will demonstrate how to develop an AWS lambda, which can be found on my github account at https://github.com/KamilBlaz/lambda-rie-boilerplate

Build our Docker image for Lambda RIE

make build

After building the image, you can run the container with the Lambda RIE server.

make local-lambda

Now you can test your lambda function via curl or postman. I am sending a request to the lambda function via curl What is important you can change the code in your IDE and Lambda will automatically rebuild your python code.

Open another console and perform the following command

curl -XPOST "http://localhost:9000/2015-03-31/functions/function/invocations" \
     -d @event.json

You should obtain response from lambda function

Note: The important thing is that watchexec is configured under python so if you would like to develop it in another language, you need to change the watchexec command in the entrypoint

Summary

In this article, I showed you how to develop AWS Lambda locally using the AWS Lambda Runtime Interface Emulator (RIE). I hope you enjoyed this article and see you next time.