How To Add NodeJs Library Dependencies in a AWS Lambda Layer with Serverless Framework

AWS announced neat Lambda Layers feature at re:Invent 2018, which gives developers up to five packages to inject into a given function at runtime. This promotes component sharing and keeps the core function package as small as possible.

Use Case

In this example, I move nodeJs runtime dependencies out of lambda function code by placing them in a layer.

To get started, update to v1.34.0 or greater for layers support and create a serverless project:

$ npm i -g serverless
$ serverless create --template aws-nodejs --path myTestLayer

To include libraries in a layer, place them in layer/nodejs/node_modules, please NOTE that the nodejs directory name is not random and must be nodejs.

Reference

AWS Lambda Layers - AWS Lambda

I m now adding lodash and moment dependencies to layer as following:

$ cd myTestLayer
$ mkdir -p layer/nodejs
$ cd layer/nodejs
$ npm install --save lodash moment

Next, add the layers config to serverless.yml to define your layer that will contain nodejs libraries. The path property is a path to a directory that will be published as your layer:

layers:
  commonLibs:
    path: layer
    compatibleRuntimes:
      - nodejs8.10

Then add your function in serverless.yml, specify that your function uses the layer you’re publishing:

functions:
  hello:
    handler: handler.hello
    layers:
        # Ref name is generated by TitleCasing the layer name & appending LambdaLayer
      - {Ref: CommonLibsLambdaLayer}

The serverless.yml should now look like:

service: myTestLayer
provider:
  name: aws
  runtime: nodejs8.10
  region: ap-southeast-2
functions:
  hello:
    handler: handler.hello
    layers:
        # Ref name is generated by TitleCasing the layer name & appending LambdaLayer
      - {Ref: CommonLibsLambdaLayer}
layers:
  commonLibs:
    path: layer
    compatibleRuntimes:
      - nodejs8.10

Now, We need to write our handler. The lambda function is a Calculator: Add or Subtract Number of Days to a Today’s Date, Replace the contents of handler.js with the following code:

"use strict";
const _ = require("lodash");
const moment = require("moment");
module.exports.hello = async (event, context, callback) => {
  const curried = _.curry(calculateDate);
  callback(null, curried(moment().format())(event));
};
const calculateDate = (datetime, days)=> {
  return moment()
    .add(days, "days")
    .format("Do MMMM YYYY, h:mm:ss a");
};

Deploy both the layer & updated function with following

$ serverless deploy

Let’s test it out by following command line:

#data is days you want to Add or Subtract to today's date
$ serverless invoke --function hello --data=2

That’s all bout it! You now get the date calculated!

For the full source of this example, check it out here.

yai333/ServerlessLambdaLayerExample

AWS Lambda Runtimes

You can now select a custom runtime when creating or updating a function. With this selection, the function must include (in its code or in a layer) an executable file called bootstrap, responsible for the communication between your code (that can use any programming language) and the Lambda environment.

New for AWS Lambda - Use Any Programming Language and Share Common Components | Amazon Web Services

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