middyjs-middleware

Middleware for use with middyjs 🛵 middyjs

Setup

Install with npm or yarn (preferred)

npm i @seedrs/middyjs-middleware --save

OR

yarn add @seedrs/middyjs-middleware

Available middleware

ensureJson

This middleware is used to ensure the client has set the Content-Type header to application/json when sending a request body. A 406 error is returned when application/json is not present in the Content-Type header. To ensure that header names are normalized use in conjunction with middyjs/middlewares/httpHeaderNormalizer and with middyjs/middlewares/jsonBodyParser to parse the incoming body for you.

const middy = require('middy');
const {
  httpHeaderNormalizer,
  jsonBodyParser
} = require('middyjs/middlewares');
const { ensureJson } = require('@seedrs/middyjs-middleware');

const handler = middy((event, context, cb) => {
  return cb(null, {});
})
.use(httpHeaderNormalizer())
.use(ensureJson())
.use(jsonBodyParser())
.use(httpErrorHandler(logger);

httpErrorHandler

This middleware is used to catch any errors thrown in your application code and return a formatted message using errors created with jshttp/http-errors. Errors are logged by the logger passed as the argument to the middleware. Intended for use with node-bunyan and @seedrs/bunyan-seedrs-serverless-serializer.

const middy = require('middy');
const createError = require('http-errors');
const { httpErrorHandler } = require('@seedrs/middyjs-middleware');

const handler = middy((event, context, cb) => {
  const error = createError.NotFoundError();
  return cb(error);
})
.use(httpErrorHandler(logger));

dynamodbStreamErrorHandler

This middleware will log errors when consuming a dynamodb stream. It is intended for use with node-bunyan and @seedrs/bunyan-seedrs-serverless-serializer.

const middy = require('middy');
const { dynamodbStreamErrorHandler
} = require('@seedrs/middyjs-middleware');

const handler = middy((event, context, cb) => {
  throw new Error('Whoops');
})
.use(dynamodbStreamErrorHandler(logger));

dynamodbStreamFilter

This middleware filters out unwanted events and ends the lambda execution early if there are no matching events in the stream. In the example below the business logic will only execute when there are Records with the INSERT event type.

const middy = require('middy');
const { dynamodbStreamFilter } = require('@seedrs/middyjs-middleware');

const handler = middy((event, context, cb) => {
  //Some business logic runs when there are INSERT events
})
.use(dynamodbStreamFilter({ eventName: 'INSERT' }));

dynamodbStreamParser

This middleware parses and extracts fields specified in the event. You can specify either to extract from the OldImage or the NewImage (if your stream is configured to show both) or specify either OldImage or NewImage.

const middy = require('middy');
const { dynamodbStreamParser } = require('@seedrs/middyjs-middleware');

const handler = middy((event, context, cb) => {
  console.log(event.Records);
  /* Shown below is the parsed stream objects
  [{
    {
      OldImage: {
        key_one: 1
      },
      NewImage: {
        key_one: 2
      }
    }
  }]
  */
})
.use(dynamodbStreamParser({
  NewImage: [
    'key_one'
  ],
  OldImage: [
    'key_one'
  ]
});

s3ErrorHandler

This middleware is intended to be used with node-bunyan and @seedrs/bunyan-seedrs-serverless-serializer. It logs the error produced along with the S3 event that triggered the invocation.

const middy = require('middy');
const { httpErrorHandler } = require('@seedrs/middyjs-middleware');

const handler = middy((event, context, cb) => {
  //Some business logic
})
.use(s3ErrorHandler(logger));

Usage without bunyan and seedrs/bunyan-seedrs-serverless-serializer

It is possible to provide a custom object that uses your own logging system with these middlewares. However we suggest using bunyan with our serializers to help parse and log events and responses as JSON. Shown below is an example using the default console object.

const middy = require('middy');
const { httpErrorHandler } = require('@seedrs/middyjs-middleware');

const handler = middy((event, context, cb) => {
  //Some business logic
})
.use(httpErrorHandler(console));

Contribute

To contribute to the project, please read the guide.