AWS Lambda Runtime Interface Emulator

The Lambda Runtime Interface Emulator is a proxy for Lambda’s Runtime and Extensions APIs, which allows customers to locally test their Lambda function packaged as a container image. It is a lightweight web-server that converts HTTP requests to JSON events and maintains functional parity with the Lambda Runtime API in the cloud. It allows you to locally test your functions using familiar tools such as cURL and the Docker CLI (when testing functions packaged as container images). It also simplifies running your application on additional computes. You can include the Lambda Runtime Interface Emulator in your container image to have it accept HTTP requests instead of the JSON events required for deployment to Lambda. This component does not emulate Lambda’s orchestrator, or security and authentication configurations. You can get started by downloading and installing it on your local machine. When the Lambda Runtime API emulator is executed, a /2015-03-31/functions/function/invocations endpoint will be stood up within the container that you post data to it in order to invoke your function for testing.

Installing

Instructions for installing AWS Lambda Runtime Interface Emulator for your platform

Platform	Command to install
macOS/Linux x86_64	`mkdir -p ~/.aws-lambda-rie && curl -Lo ~/.aws-lambda-rie/aws-lambda-rie https://github.com/aws/aws-lambda-runtime-interface-emulator/releases/latest/download/aws-lambda-rie && chmod +x ~/.aws-lambda-rie/aws-lambda-rie`
macOS/Linux arm64	`mkdir -p ~/.aws-lambda-rie && curl -Lo ~/.aws-lambda-rie/aws-lambda-rie https://github.com/aws/aws-lambda-runtime-interface-emulator/releases/latest/download/aws-lambda-rie-arm64 && chmod +x ~/.aws-lambda-rie/aws-lambda-rie`
Windows x86_64	`Invoke-WebRequest -OutFile 'C:\Program Files\aws lambda\aws-lambda-rie' https://github.com/aws/aws-lambda-runtime-interface-emulator/releases/latest/download/aws-lambda-rie`
Windows arm64	`Invoke-WebRequest -OutFile 'C:\Program Files\aws lambda\aws-lambda-rie' https://github.com/aws/aws-lambda-runtime-interface-emulator/releases/latest/download/aws-lambda-rie-arm64`

Getting started

There are a few ways you use the Runtime Interface Emulator (RIE) to locally test your function depending on the base image used.

Test an image with RIE included in the image

The AWS base images for Lambda include the runtime interface emulator. You can also follow these steps if you built the RIE into your alternative base image.

To test your Lambda function with the emulator

Build your image locally using the docker build command.

docker build -t myfunction:latest .
Run your container image locally using the docker run command.

docker run -p 9000:8080 myfunction:latest

This command runs the image as a container and starts up an endpoint locally at localhost:9000/2015-03-31/functions/function/invocations.
Post an event to the following endpoint using a curl command:

curl -XPOST "http://localhost:9000/2015-03-31/functions/function/invocations" -d '{}'

This command invokes the function running in the container image and returns a response.

Build RIE into your base image

You can build RIE into a base image. Download the RIE from GitHub to your local machine and update your Dockerfile to install RIE.

To build the emulator into your image

Create a script and save it in your project directory. Set execution permissions for the script file.

The script checks for the presence of the AWS_LAMBDA_RUNTIME_API environment variable, which indicates the presence of the runtime API. If the runtime API is present, the script runs the runtime interface client. Otherwise, the script runs the runtime interface emulator.

The following example shows a typical script for a Node.js function.
```
#!/bin/sh
if [ -z "${AWS_LAMBDA_RUNTIME_API}" ]; then
  exec /usr/local/bin/aws-lambda-rie /usr/bin/npx aws-lambda-ric
else
  exec /usr/bin/npx aws-lambda-ric
fi
```
Download the runtime interface emulator for your target architecture (aws-lambda-rie for x86_64 or aws-lambda-rie-arm64 for arm64) from GitHub into your project directory.
Install the emulator package and change ENTRYPOINT to run the new script by adding the following lines to your Dockerfile:

To use the default x86_64 architecture
```
ADD aws-lambda-rie /usr/local/bin/aws-lambda-rie
ENTRYPOINT [ "/entry_script.sh" ]
```
To use the arm64 architecture:
```
ADD aws-lambda-rie-arm64 /usr/local/bin/aws-lambda-rie
ENTRYPOINT [ "/entry_script.sh" ]
```
Build your image locally using the docker build command.
```
docker build -t myfunction:latest .
```
Run your image locally using the docker run command.
```
docker run -p 9000:8080 myfunction:latest
```

Test an image without adding RIE to the image

You install the runtime interface emulator to your local machine. When you run the container image, you set the entry point to be the emulator.

To test an image without adding RIE to the image

From your project directory, run the following command to download the RIE (x86-64 architecture) from GitHub and install it on your local machine.

mkdir -p ~/.aws-lambda-rie && curl -Lo ~/.aws-lambda-rie/aws-lambda-rie \
https://github.com/aws/aws-lambda-runtime-interface-emulator/releases/latest/download/aws-lambda-rie \
&& chmod +x ~/.aws-lambda-rie/aws-lambda-rie

To download the RIE for arm64 architecture, use the previous command with a different GitHub download url.

https://github.com/aws/aws-lambda-runtime-interface-emulator/releases/latest/download/aws-lambda-rie-arm64 \

Run your Lambda image function using the docker run command.
```
docker run -d -v ~/.aws-lambda-rie:/aws-lambda -p 9000:8080 myfunction:latest \
    --entrypoint /aws-lambda/aws-lambda-rie  <image entrypoint> <(optional) image command>
```
This runs the image as a container and starts up an endpoint locally at localhost:9000/2015-03-31/functions/function/invocations.
Post an event to the following endpoint using a curl command:
```
curl -XPOST "http://localhost:9000/2015-03-31/functions/function/invocations" -d '{}'
```
This command invokes the function running in the container image and returns a response.

How to configure

aws-lambda-rie can be configured through Environment Variables within the local running Image. You can configure your credentials by setting:

AWS_ACCESS_KEY_ID
AWS_SECRET_ACCESS_KEY
AWS_SESSION_TOKEN
AWS_REGION

You can configure timeout by setting AWS_LAMBDA_FUNCTION_TIMEOUT to the number of seconds you want your function to timeout in.

The rest of these Environment Variables can be set to match AWS Lambda's environment but are not required.

AWS_LAMBDA_FUNCTION_VERSION
AWS_LAMBDA_FUNCTION_NAME
AWS_LAMBDA_FUNCTION_MEMORY_SIZE

Level of support

You can use the emulator to test if your function code is compatible with the Lambda environment, executes successfully and provides the expected output. For example, you can mock test events from different event sources. You can also use it to test extensions and agents built into the container image against the Lambda Extensions API. This component does not emulate the orchestration behavior of AWS Lambda. For example, Lambda has a network and security configurations that will not be emulated by this component.

You can use the emulator to test if your function code is compatible with the Lambda environment, runs successfully and provides the expected output.
You can also use it to test extensions and agents built into the container image against the Lambda Extensions API.
This component does not emulate Lambda’s orchestration, or security and authentication configurations.
The component does not support X-ray and other Lambda integrations locally.
The component supports only Linux, for x86-64 and arm64 architectures.

Security

See CONTRIBUTING for more information.

License

This project is licensed under the Apache-2.0 License.

License

localstack/lambda-runtime-init

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