lambda-lambda-lambda

lambda-lambda-lambda

AWS Lambda@Edge serverless application router.

Features

• Routes and URI Resource support.
• Local/Globally scoped Middleware.
• Request/Response handling API.
• Lightweight (no dependencies).
• Pay-per-use priced solution.

Dependencies

• AWS SAM CLI
• Node.js

Getting started

The easiest way to build a new application, without the need to manually install this package, is to use the Lambda Lambda Lambda VS Code extension which allows you to:

• Scaffold app sources and dependencies.
• Run it locally (in Remote - Containers)
• Test code changes in realtime.
• Deploy app sources to AWS.
• Generate JSDoc/Swagger documentation.

Installation

Install package dependencies using NPM.

$ npm install lambda-lambda-lambda

Usage

Unless your application requires complex routing, route handlers can be defined within the Lambda function scope. Otherwise route handlers are loaded from appName/src/routes directory in hierarchical order, starting with the default handler appName/src/app.js as described below.

Synchronous example

// .. appName/src/app.js

'use strict';

// Load module.
const Router = require('lambda-lambda-lambda');

/**
 * @see AWS::Serverless::Function
 */
exports.handler = (event, context, callback) => {
  const {request, response} = event.Records[0].cf;

  const router = new Router(request, response);
  router.setPrefix('/api'); // optional, default /

  // Middleware (order is important).
  router.use(function(req, res, next) {
    if (req.method() === 'CONNECT') {
      res.status(405).send();
    } else {
      next(); // Run subsequent handler
    }
  });

  // Send root response.
  router.get('/', function(req, res) {
    res.status(501).send();
  });

  // .. everything else.
  router.default(function(req, res) {
    res.status(404).send();
  });

  callback(null, router.response());
};

Asynchronous example

// .. appName/src/app.js

'use strict';

// Load module.
const Router = require('lambda-lambda-lambda');

/**
 * @see AWS::Serverless::Function
 */
exports.handler = async (event) => {
  const {request, response} = event.Records[0].cf;

  const router = new Router(request, response);

    ..

  return await router.response();
};

Common methods

The following methods are supported based on the class context. For further information please refer to the JSDoc generated documentation which includes method arguments/return types and general usage examples.

Router Method	Description
router.setPrefix(path)	Set URI path prefix.
router.use(func)	Load the Route (e.g. Middleware) handler.
router.get(path, func)	Handle HTTP GET requests.
router.put(path, func)	Handle HTTP PUT requests.
router.patch(path, func)	Handle HTTP PATCH requests.
router.post(path, func)	Handle HTTP POST requests.
router.delete(path, func)	Handle HTTP DELETE requests.
router.default(func)	Set router fallback (default route).
router.response()	Return the AWS response object.

Request Method	Description
req.is(mimeType)	Check Accept matches the given value.
req.header(name)	Return value for given HTTP header name.
req.getHeaders()	Return the headers of the request.
req.method()	Return the HTTP method of the request.
req.uri()	Return the relative path of the requested object.
req.clientIp()	Return the HTTP client IP (remote address).
req.param(name)	Return the HTTP request parameters or name/value.
req.queryString()	Return the serialized query parameters.
req.body()	Return the base64-encoded body data.

Response Method	Description
res.setHeader(name, value)	Set HTTP response header.
res.status(code).send(body)	Send the HTTP response (Array, Buffer, Object, String).
res.status(code).data(buffer)	Send binary data with HTTP response.
res.status(code).json(obj)	Send the HTTP response as JSON.
res.status(code).text(str)	Send the HTTP response as text.

Complex routing

When constructing a routing handler the following methods/aliases are supported. While they can be used interchangeably they must define either a Route or Resource handler, but not both.

Handler Method	Alias
get	index
post	submit
put	create
patch	update
delete	N/A

Route handler

// .. appName/src/routes/foo.js

'use strict';

// Load module.
const contentTypeHeader = require('middleware/ContentTypeHeader');

/**
 * @export {Object}
 */
module.exports = {
  middleware: [contentTypeHeader], // Locally scoped.

  /**
   * GET /api/foo
   */
  index (req, res) {
    res.status(200).send('Lambda, Lambda, Lambda');
  },

  /**
   * PUT /api/foo
   */
  create (req, res) {
    res.status(201).send();
  },

  /**
   * PATCH /api/foo
   */
  update (req, res) {
    res.status(204).send();
  },

  /**
   * DELETE /api/foo
   */
  delete (req, res) {
    res.status(410).send();
  },

  /**
   * POST /api/foo
   */
  submit (req, res) {
    res.status(200).send();
  }
};

Resource handler

// .. appName/src/routes/foo/bar.js

'use strict';

/**
 * @export {Object}
 */
module.exports = {
  resource: true,

  /**
   * GET /api/foo/bar/<resourceId>
   */
  get (req, res, id) {
    res.setHeader('Content-Type', 'application/json');
    res.status(200).json({and: 'Omega Mu'});
  },

  /**
   * PUT /api/foo/bar/<resourceId>
   */
  put (req, res, id) {
    res.status(201).send();
  },

  ..
};

Mixed Route/Resource handler

// .. appName/src/routes/foo.js

'use strict';

/**
 * @export {Object}
 */
module.exports = {
  resource: ['put'],

  /**
   * GET /api/foo
   */
  index (req, res) {
    res.setHeader('Content-Type', 'text/html');
    res.status(200).send('Lambda, Lambda, Lambda');
  },

  /**
   * PUT /api/foo/<resourceId>
   */
  get (req, res, id) {
    res.setHeader('Content-Type', 'application/json');
    res.status(200).json({and: 'Omega Mu'});
  },

  ..
};

Middleware

// .. appName/src/middleware/ContentTypeHeader.js

'use strict';

/**
 * Middleware to send Content-Type header.
 */
module.exports = (req, res, next) => {
  res.setHeader('Content-Type', 'text/html');

  next(); // Run subsequent handler.
};

See restfulApiHandler example for more complex use cases.

AWS requirements

In order to successfully deploy your application you must have set-up your AWS Config and have created an IAM user with the following policies:

• IAMFullAccess
• CloudFrontFullAccess
• AWSCloudFormationFullAccess
• AWSLambda_FullAccess

WARNING: The policies above are provided to ensure a successful application deployment. It is recommended that you adjust these policies to meet the security requirements of your Lambda application. They should NOT be used in a Production environment.

Developers

CLI options

Run ESLint on project sources:

$ npm run lint

Generate documentation using JSDoc:

$ npm run gendoc

Run Mocha integration tests:

$ npm run test

References

• Restrictions on edge functions

Motivation

I was looking for a light-weight API driven routing system (limited dependencies, easy to audit) that didn't require API Gateway integration (Lambda/CloudFront only) but could be distributed globally and cached for cheap. And finally, I wanted an unopionionated way to consolidate application code and dependencies to a single Lambda/CloudFront behavior.

Well, my search came short so I wrote this.

Contributions

If you fix a bug, or have a code you want to contribute, please send a pull-request with your changes. (Note: Before committing your code please ensure that you are following the Node.js style guide)

Versioning

This package is maintained under the Semantic Versioning guidelines.

License and Warranty

This package is distributed in the hope that it will be useful, but without any warranty; without even the implied warranty of merchantability or fitness for a particular purpose.

lambda-lambda-lambda is provided under the terms of the MIT license

AWS is a registered trademark of Amazon Web Services, Inc.

Author

Marc S. Brooks