business logic Focus on business logic Scalability Scalability Pay per usage model (compute time * memory) Pay per usage model (compute time * memory) Managed infrastructure Managed infrastructure Forces you to think micro-services Forces you to think micro-services @loige 6
weekly newsletter ( ) A middleware framework for AWS Lambda ( ) Enterprise Trading, Billing engine, Market data aggregator solutions ( ) Big data pipeline to make network metadata searchable ( ) Organised various workshops around Europe ( ) Fullstack bulletin middy.js.org ESB Vectra.ai Serverlesslab.com @loige 7
up ♀ 1. Use the APIs to create a dashboard that contains: 1. Use the APIs to create a dashboard that contains: An IrishRail station widget A LUAS stop widget A DublinBus stop widget (there are utility scripts to list all the stops and stations, check the README) 2. Have a look at the code 2. Have a look at the code If you find bugs, please send a or report an PR issue @loige 21
get input from event and context // use callback to return output or errors } Anatomy of a Node.js lambda on AWS Anatomy of a Node.js lambda on AWS @loige 24
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 A typical "REAL" Lambda function @loige 25
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 A typical "REAL" Lambda function @loige 25
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 A typical "REAL" Lambda function @loige 25
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 A typical "REAL" Lambda function LOTS of BOILERPLATE @loige 25
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 @loige 33
= 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 } @loige 35
the next exercises we will need the full power of middy, so to get started let's just "middify" all our handlers — Note: handlers are defined in "src/handlers", and they get used in "src/handler.js". You can either middify every single handler file or middify them when used in src/handler.js. In the first case, make sure you middify the actual handler function and not the "handler factory". ( ) a solution @loige 37
are manually deserializing the JSON input in our APIs. We can simplify the code a bit by using the middleware. — Install @middy/http-json-body-parser and remove all the instances of JSON.parse() in our handlers. ( ) http-json-body-parser a solution @loige 38
actually not even dealing with errors right now... by using the middleware we will be able to handle all HTTP errors and return codes consistently. — Install @middy/http-error-handler and apply that to all our handlers. ( ) http-error-handler a solution Exercise 2 Exercise 2: what if we fail? : what if we fail? @loige 39
being written to the database. We can use the middleware for this task! — Install @middy/validator and apply that to all our POST API handlers. You can use to define your schemas or, if you are struggling, you can find some schemas ready-made for you :) Note: The validator should be added after the json-body-parser, so you can validate individual fields of the input data. ( ) validator jsonschema.net here a solution Exercise 3 Exercise 3: validate! : validate! @loige 40
JSON is definitely not the friendliest experience! It would be much better to do in a properly rendered HTML so that we could easily visualize them on our mobile device! — You can implement this in (at least) 2 ways : Using the middleware and building a frontend somewhere like or Using the middleware and implementing a specific rule for accept "text/html" ( - ) http-cors codesandbox codepen http-content-negotiation a CORS solution a CodeSandbox React UI Exercise 4 Exercise 4: mobile rendering : mobile rendering @loige 41
the endpoint and the id, anyone can basically change or delete the dashboards! That's unacceptable! — Find a way to secure the APIs. One easy way could be to create a secret random token when a dashboard is created the first time. Then you can create a custom middleware that checks the secret every time someone is trying to modify or delete that dashboard! Note: if you feel fancy you can use JWT tokens, in such case you could take inspiration from the middleware! jwt-auth Exercise 5 Exercise 5: better safe than sorry : better safe than sorry @loige 42
to answer. This is because of a common serverless issue known as " ". If you are running for your train every morning, this is unacceptable! We should fix this... — Use the middleware to mitigate the cold start issue Note: make sure to also setup the proper event for every API. cold start problem warmup schedule 2 @loige Exercise 6 Exercise 6: stop the cold!
APIs to build a shiny SWING UI... The problem is that they don't really like JSON and they would rather have a good old XML-based API. You might think that this is actually their problem, but also, you don't want to lose your friends... — Use the middleware to provide responses in XML for accept "application/xml". Note: You could use a library like to automate the conversion of JavaScript objects to XML. http-content-negotiation json2xml @loige Exercise 7 Exercise 7: legacy friendship : legacy friendship 44
to build apps quickly and with a greater focus on business logic, rather than on infrastructure! Middy helps you to keep focusing on your business logic first You can add extra behaviours with very minimal changes to your core logic by introducing dedicated middlewares You can easily share common functionality through middlewares 45
Use it Give feedback Give feedback Contribute (I am looking for co-maintainers) Contribute (I am looking for co-maintainers) Version 1.0 (stable) coming soon Version 1.0 (stable) coming soon 46
to all the amazing Middy users and ! Thanks to for reviewing these slides and to for finding lots of bugs! TotumRevolutum Pixabay contributors @StefanoAbalsamo @organicdelight @loige 48
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