lambda-alb

A mock ALB using express that enables invoking a lambda locally using HTTP.

It supports multple lambda's mapped to various routes. Can be configured to use either a mock AWS setup, such as localstack, or an actual AWS region.

GitHub Repo: https://github.com/djfdyuruiry/lambda-alb

Docker Hub: https://hub.docker.com/r/djfdyuruiry/lambda-alb

Read the full typedoc documentation: https://djfdyuruiry.github.io/lambda-alb/

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Getting Started

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• Install this package using npm

npm install -g lambda-alb

• Deploy some code to an AWS Lambda Function that processes ALB or API Gateway request events (see here)

• Create a new JSON file config.json, add the following:

{
    "region": "eu-west-1",
    "targets": {
        "some-lambda":{
            "lambdaName": "some-lambda-function"
        },
        "another-lambda":{
            "lambdaName": "another-lambda-function"
        }
    }
}

Ensure the region of your function is correct when copying the above

• Ensure that your AWS credentials are set up correctly, see here if you need help doing this

• Start the ALB mock using your new config file:

lambda-alb --config config.json

• Start making requests using the target routes:

curl http://localhost:8080/some-lambda/
curl http://localhost:8080/another-lambda/

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Local AWS Mocks

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If you are using a local AWS Mock to run your lambda's, specify it's endpoint in the JSON configuration file:

{
    "lambdaEndpoint": "http://localhost:4574",
    "targets": {
        "some-lambda":{
            "lambdaName": "some-lambda-function"
        }
    }
}

If you get errors similar to Missing credentials in config, run the below to set mock credential env vars before starting lambda-alb:

export AWS_ACCESS_KEY_ID=MOCK
export AWS_SECRET_ACCESS_KEY=MOCK

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Docker

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To use the image:

• Place a config.json file in the current directory containing your setup

• Run the below commands:

  dokcer run --rm -v $(pwd):/etc/lambda-alb -p 8080:8080 djfdyuruiry/lambda-alb

  Don't forget to pass your AWS credentials in as environment variables, or mount a volume to supply a credentials file. See here for more info.

• You can now access your lambda-alb on http://localhost:8080

docker-compose

If you are using docker-compose it's very simple to add lambda-alb to your stack:

version: "3"
 
services:
  alb:
    image: djfdyuruiry/lambda-alb.git
    ports:
      - 8080:8080
    volumes:
      - ${PWD}/config.json:/etc/lambda-alb/config.json

Building

A Dockerfile is provided in this repository that will create an image containing the latest version of this package on the global path.

docker build --tag djfdyuruiry/lambda-alb .

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Command Line Arguments

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lambda-alb supports several command line parameters:

• -c or --config: Path to JSON configuration file
• -p or --port: (Optional) Port to listen on, defaults to 8080
• -h or --host: (Optional) Host to accept requests on, defaults to * (any hostname/ip)
• -o or --cors-origin: (Optional) CORS origins to allow, defaults to * (any origin)
• -d or --debug: (Optional) Enable debug logging

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Configuration

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Below is an overview of the JSON configuration file schema:

Key	Description	Example	Required?
region	AWS region that your Lambda targets have been deployed to	eu-west-1	✘
lambdaEndpoint	Custom service endpoint for AWS Lambda	http://localhost:4574	✘
targets	Map of target route to AWS Lambda definition	{ "some-lambda": { "lambdaName": "some-lambda-function "} }	✔

AWS Lambda Definition (targets) schema:

Key	Description	Example	Required?
lambdaName	Name of the target Lambda function	a-lambda-name	✔
versionOrAlias	A version or alias of the function to invoke	DEV	✘
routeUrl	Override the target route for this Lambda	/special-route	✘