Create AWS Lambda layer with serverless framework (node.js)

When developing Lambda with node.js, npm packages are essential.

However, if every Lambda function has its own node_modules, it becomes heavy. As a result, you can’t see the Lambda code from the console!

What should you do? After searching, I found AWS Lambda Layers. By using this, you can upload libraries as a Layer and have your Lambdas use the uploaded Layer.

Layers can be used from the console, but in real development, you rarely use the console. So this time, I’ll make a note of the method using the serverless framework, which I often use.

Environment

macOS Catalina
- 10.15.4
serverless framework
- Framework Core: 1.67.3 (standalone)
- Plugin: 3.6.6
- SDK: 2.3.0
node.js
- v12.15.0
aws
- aws-cli/1.18.0 Python/3.7.3 Darwin/19.4.0 botocore/1.15.0

Create a service using serverless framework

Since it’s node.js, use the aws-nodejs template.

% sls create --template aws-nodejs --path sls-layer

Install npm packages

Create a layer folder directly under the directory. The structure looks like this:

├── handler.js
├── my-layer  ← Directory to store the layer
│   └── nodejs
│
└── serverless.yml

Move to the nodejs folder. Install the npm package. Here, I’ll use hello-world-npm as an example.

nodejs% npm init -y
nodejs% npm i hello-world-npm

After completing these steps, the folder structure should look like this:

├── handler.js
├── my-layer  ← Directory to store the layer
│   └── nodejs
│       └── node_modules
│       └── package-lock.json
│       └── package.json
│
│
└── serverless.yml

Configure serverless.yml

service: sls-layer

provider:
  name: aws
  runtime: nodejs12.x

functions:
  hello:
    handler: handler.hello
    layers:
      - {Ref: MylayerLambdaLayer}

layers:
  mylayer:
    path: my-layer

The configuration is relatively simple. You just use the built-in function Ref to return the specified parameter or resource.

After that, you just need to call hello-world-npm in your Lambda function.

'use strict';

const helloWorld = require('hello-world-npm')

module.exports.hello = async event => {
  return {
    statusCode: 200,
    body: JSON.stringify(
      {
        message: helloWorld(),
        input: event,
      },
      null,
      2
    ),
  };
};

That’s it. Just to make sure everything works, I checked it, and it works fine.

% sls invoke -f hello
{
    "statusCode": 200,
    "body": "{\n  \"message\": \"Hello World NPM\",\n  \"input\": {}\n}"
}

I also checked on the AWS Console.

The layers are added correctly.

AWS Lambdaのlayerをserverless frameworkでつくる(node.js)

On the function code side, the node_modules, package.json, and other files are gone, making it neat and clean.

AWS Lambdaのlayerをserverless frameworkでつくる(node.js)