Introducing Middy, Node.js middleware engine for AWS Lambda (FrontConf Munich 2017 — Lightning talk)

Introducing Middy, Node.js middleware engine for AWS Lambda (FrontConf Munich 2017 — Lightning talk)

• 1.
  Introducing The stylish Node.jsmiddleware engine for AWS Lambda middy.js.org Luciano Mammino ( )@loige Munich, 9 Nov 2017 1
• 2.
  loige.link/middy-intro 2
• 3.
  Luciano... who? Let's connect (@loige) (lmammino) Twitter GitHub Linkedin https://loige.co ...just a Fullstack developer 3
• 4.
  The problem withLambdas 4
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  exports.myLambda = function( event, context, callback ) { // get input from event and context // use callback to return output or errors } Anatomy of a Node.js lambda on AWS 5
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  (event, context, callback)=> { // decrypt environment variables with KMS // deserialize the content of the event // validate input, authentication, authorization // REAL BUSINESS LOGIC // (process input, generate output) // validate output // serialize response // handle errors } A typical "REAL" Lambda function LOTS of BOILERPLATE 😓😓 6
• 7.
  The solution 7
• 8.
  npm install middy 8
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  Usage const middy =require('middy') const { middleware1, middleware2, middleware3 } = require('middy/middlewares') const originalHandler = (event, context, callback) => { /* your business logic */ } const handler = middy(originalHandler) handler .use(middleware1()) .use(middleware2()) .use(middleware3()) module.exports = { handler } 9
• 10.
  const middy =require('middy') const { urlEncodedBodyParser, validator, httpErrorHandler } = require('middy/middlewares') const processPaymentHandler = (event, context, callback) => { const { creditCardNumber, expiryMonth, expiryYear, cvc, nameOnCard, amount } = event.body // do stuff with this data ... return callback(null, { result: 'success', message: 'payment processed correctly'} ) } const inputSchema = { // define validation schema here ... } const handler = middy(processPaymentHandler) .use(urlEncodedBodyParser()) .use(validator(inputSchema)) .use(httpErrorHandler()) module.exports = { handler } 10
• 11.
  Why? Simplify code Reusability input parsing input& output validation output serialization error handling ... Focus MORE on business logic 11
• 12.
  How it works 12
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  Execution order 1. middleware1(before) 2. middleware2 (before) 3. middleware3 (before) 4. handler 5. middleware3 (after) 6. middleware2 (after) 7. middleware1 (after) 13
• 14.
  When an errorhappens... Flow is stopped First middleware implementing `onError` gets control It can choose to handle the error, or delegate it to the next handler If the error is handler a response is returned If the error is not handled the execution fails reporting the unhandled error 14
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  Writing a middleware constmyMiddleware = (config) => { // might set default options in config return ({ before: (handler, next) => { // might read options from `config` }, after: (handler, next) => { // might read options from `config` }, onError: (handler, next) => { // might read options from `config` } }) } module.exports = myMiddleware 15
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  Inline middlewares const middy= require('middy') const handler = middy((event, context, callback) => { // do stuff }) handler.before((handler, next) => { // do something in the before phase next() }) handler.after((handler, next) => { // do something in the after phase next() }) handler.onError((handler, next) => { // do something in the on error phase next() }) module.exports = { handler } 16
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  Currently availble middlewares JSONBody Parser Url Encoded Body Parser Validator HTTP Error Handler CORS S3 Key Normalizer Do Not Wait for event loop Support for async/await handlers (just return, don't need to use callback) XML Body parser API Gateway Event normalizer In development 17
• 18.
  That's all folks (fornow!) middy.js.org THANKS! 18