Package Exports

lambda-request-handler

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Readme

lambda-request-handler

An npm module that allows your Express.js or Connect web applications to be deployed as an AWS Lambda function

Inspired by aws-serverless-express

It supports nodejs8.10 and nodejs10.x execution environments.

The main differences between this module and aws-serverless-express are

It's using in-process-request module to execute app handlers in-process without having to start background http server
Simpler setup as it doesn't require managing the internal http server
It's faster, because it doesn't need to pass the request to the internal server through the unix socket
It's free from issues caused by limits in Node.js http module such as header size limit

Usage

The default export of lambda-request-handler is a function that takes an application handler (i.e. Express.js app instance) as an argument and returns an AWS Lambda handler function.

$ npm install lambda-request-handler

const express = require('express')
const lambdaRequestHandler = require('lambda-request-handler')

cont app = express()

app.get('/user/:id', (req, res) => {
  res.json({
    id: req.params.id,
    name: 'John'
  })
})

const handler = lambdaRequestHandler(app)

module.exports = { handler }

If the above file in your Lambda source was called index.js then the name of the handler in the Lambda configuration is index.handler

Advanced example

Sometimes the application needs to read configuration from remote source before it can start processing requests. For example it may need to decrypt some secrets managed by KMS.

const lambdaRequestHandler = require('lambda-request-handler')
const AWS = require('aws-sdk')
const express = require('express')

const kms = new AWS.KMS()

const myKmsPromise = () =>
  kms.decrypt({
    CiphertextBlob: Buffer.from(process.env.ENCRYPTED_SECRET, 'base64')
  })
  .promise()
  .then((data) => {
    process.env.SECRET = data.Plaintext.toString('ascii')
  });

cont app = express()

app.get('/secret', (req, res) => {
  res.json({
    secret: process.env.SECRET,
  })
})

const myAppHandler = lambdaRequestHandler(app)

let _myKmsPromise;

const handler = (event) => {
  if (!_myKmsPromise) {
    // _myKmsPromise is in global scope so that only one request to KMS is made during this Lambda lifecycle
    _myKmsPromise = myKmsPromise();
  }
  return _myKmsPromise
    .then(() => {
      // at this point the secret is decrypted and available as process.env.SECRET to the app
      return myAppHandler(event);
    })
}

module.exports = { handler }