lambdify

lambdify

Lambdify is a set of tools that makes building and consuming AWS Lambda functions easier.

Getting Started

Basic HTTP Lambda Function - JSON Response

const lambdify = require('lambdify');

const helloWorld = (request, response) => {
  response.json({ message: `Hello User, I see that you are coming from IP: ${request.getIp()}` });

  return response;
};

exports.handler = lambdify(helloWorld);

Basic HTTP Lambda Function - HTML Response

const lambdify = require('lambdify');

const helloWorld = (request, response) => {
  response.html(`Hello User, I see that you are coming from IP: ${request.getIp()}`);

  return response;
};

exports.handler = lambdify(helloWorld);

Basic S3 Trigger

const lambdify = require('lambdify');
const AWS = require('aws-sdk');
const s3 = new AWS.S3({ apiVersion: '2006-03-01' });

const run = async (request) => {
  const { bucket, key } = request.getS3();
  const file = await s3.getObject({ Bucket: bucket, Key: key }).promise();

  if (file && file.Body) {
    // Do something with the file
  }
};

exports.handler = lambdify(run);

Installation

npm i lambdify

or

yarn add lambdify

lambdify(fn, middleware = [])

Lambdify accepts a function and an array of middleware

const lambdify = require('lambdify');
const errorMiddleware = require('errorMiddleware');

const run = (request, response) => {
  response.json({ foo: 'bar' });

  return response;
};

exports.handler = lamdify(run, [errorMiddleware]);

request

This is the request object that is built from the lambda event

• request.get(name) - Get a value of name from a basic key value store
• request.getAuthToken() - Get the authorization token from the request
• request.getBody() - Get the body of the event and parse into an object if JSON
• request.getContext() - Get the lambda context
• request.getCookie(name) - Get value of cookie name from API Gateway Request
• request.getCookies() - Get all cookies from API Gateway Request
• request.getEvent() - Get lambda event
• request.getHeader(name) - Get value of header name from API Gateway Request
• request.getHeaders() - Get all headers from API Gateway Request
• request.getIp() - Get remote ip (handles X-Forwarded-For)
• request.getMethod() - Get HTTP request method from API Gateway Request
• request.getPath() - Get URL path from API Gateway Request
• request.getPathParams() - Get path paramaters from API Gateway Request
• request.getQueryParam(name) - Get value of query parameter name from API Gateway Request
• request.getQueryParams() - Get query parameters from API Gateway Request
• request.getS3() - Get bucket and key from S3 Trigger
• request.getSns() - Get record from SNS Trigger
• request.getSqs() - Get records from SQS Trigger
• request.getUa() - Get UserAgent from API Gateway Request
• request.set(name, value) - Set a value of name into a basic key value store

response

This is the response object that must be returned from your lambda function (or middleware)

Methods binary, html, json, redirect, xml can be returned directly

• response.binary(base64 | buffer, contentType)- Build a binary response
• response.enableCors()- Enable CORS for an API Gateway response
• response.getBody()- Get the body of the response
• response.getHeader(name)- Get the value of header name
• response.getHeaders()- Get all headers
• response.getResponse()- Get the lambda response object
• response.getStatusCode()- Get the status code of the response
• response.html(body)- Build an html response
• response.json(body)- Build a json response
• response.file(filePath, contentType)- Sends file
• response.redirect(url, statusCode = 302)- Build a redirect response
• response.setBinaryResponse(value)- Set the response as a binary response for API Gateway
• response.setBody(body)- Set the body of the response
• response.setHeader(name, value)- Set value of header name
• response.setStatusCode(value)- Set the status code of the response
• response.xml(body)- Build an xml response

Middleware

Middleware allows you to wrap your function with another function in such a way that you can execute code before or after your function runs. This is useful for instantiating database connections or error handling

Example: simple middleware

const middleware = async (req, res, next) => {
  const response = await next(req, res);

  response.setHeader('Cookie', 'test=this');

  return response;
};

module.exports = middleware;

Usage:

const lambdify = require('lambdify');
const middleware = require('./middleware');

const run = (request, response) => {
  response.json({ foo: 'bar' });

  return response;
};

exports.handler = lamdify(run, [middleware]);

Example: error middleware

const errorMiddleware = async (req, res, next) => {
  try {
    const response = await next(req, res);

    return response;
  } catch (error) {
    // Fire off log to error system like raygun / sentry

    res.setStatusCode(500);

    return res.json({
      message: error.message,
      stack: error.stack,
      status: 'error',
    });
  }
};

module.exports = errorMiddleware;

Usage:

const lambdify = require('lambdify');
const errorMiddleware = require('./errorMiddleware');

const run = (request, response) => {
  response.json({ foo: 'bar' });

  return response;
};

exports.handler = lamdify(run, [errorMiddleware]);

Example: knex middleware

const knex = (config) => async (req, res, next) => {
  const knex = require('knex')(config);

  req.set('knex', knex);

  try {
    const response = await next(req, res);

    await knex.destroy();

    return response;
  } catch (error) {
    await knex.destroy();

    throw error;
  }
};

module.exports = knex;

Usage:

const lambdify = require('lambdify');
const knexMiddleware = require('./knexMiddleware');

const run = (request, response) => {
  const knex = request.get('knex');
  const user = knex('user').where({ id: request.getPathParam('userId') });

  response.json({ user });

  return response;
};

exports.handler = lamdify(run, [knexMiddleware(dbConfig)]);

Router

Lambdify provides a router to enable your to attach a lambda to an ALB endpoint or a proxy+ api gateway path

Example

const lambdify = require('lambdify');
const router = require('lambdify/router')(); # Mind the double parentheses here

const index = (req, res) => res.json({ foo: 'bar' });

router.path('get', '/', index);

exports.handlers = lambdify(router.serve);

router.path(httpMethod, path, fn, ...middleware)

This will match the method and path. The path can be a valid url path defined here

router.sqs(key/fn, [value, fn], ...middleware)

If key, value, fn are provided, it will match on the matching key / value inside the sqs request payload (single SQS message only). If just fn is provided, it will execute the fn when there is an SQS event

router.serve

This is the fn that lambdify accepts

Helpers

Lambdify provides a couple of helpers to help consume other local lambda functions and build / extend events.

invoke(event, fn)

Invoke is used to invoke other local lambda code correctly irregardless if the function uses callback, context or a standard response.

• event is the event payload that your lambda accepts. See event below for event creation
• fn is the function handler

Example

const lambdify = require('lambdify');
const { event, invoke } = require('lambdify/helpers');

const run = (req, res) => {
  const newEvent = event(req.getEvent(), { foo: 'bar' });
  const fn = require('./otherProjectLambdaFunction/turnBarToBaz').handler;
  const response = await invoke(newEvent, fn);

  return res.json((JSON.parse(response.body));
  // => { foo: 'baz' }
};

exports.handler = lambdify(run);

event(originalEvent = {}, body = {}, overrides = {})

The goal of event is to ensure a consistent event payload to be sent to other lambda functions in a clean and consistent structure

• originalEvent is the original event object you wish to extend
• body is the new body payload being sent that is automatically JSON.stringify'ed
• overrides is an object that will override anything else in the original event

Lambda Web Server / Express

Run a webserver on your lambda instance! Express, Koa, etc should now run without a hitch.

This is very similar to aws-serverless-express. The main point being, it's a little more clean and simple to understand

Example

Your Lambda Handler (usually index.js)

const lambdaServer = require('lambdify/server');
const app = require('./app');

exports.handler = lambdaServer(app);

app.js

const express = require('express');
const app = express();

app.get('/', (req, res) => res.send('Hello World!'));

module.export = app;

And for testing locally (I like to name it server.js)

const app = require('./app.js');

app.listen(3000, () => console.log('Now Listening'));

Why not use aws-serverless-express

This focuses on simplicity and standard use cases. It also doesn't worry about legacy implementations of lambda callback / context use and is focused on Node 10 / 12 support only with an emphasis on async / await code

Other inspiration

This was originally developed to handle next.js SSR on AWS Lambda. Officially there is no support and although packages like serverless-nextjs-plugin exist, they require more packages and the serverless deployment system.