lessware-aws

aws middleware for lessware framework

Install

npm i -S lessware-aws

API

waitsForEmptyEventLoop - a function that returns the middleware function which mutates a Lambda function's callbackWaitsForEmptyEventLoop property.

• input parameter: an object whose keys determine behavior,
  • toWait - a function whose input is the context from the middleware and returns a boolean (default false) used to tell Lambda if it should wait for all asynchronous activity to resolve
  • contextKey - the key (default "ctx") storing a Lambda Function's 2nd parameter often called "context"
• output: the middleware function for lessware's framework usage.

service - a function that returns the middleware function that attaches an instance of a service instance of the AWS SDK.

• input parameter: an object whose keys determine behavior,
  • service a string that will be used to store the service instance on the context object under a key called aws, e.g. context.aws.secrets may store the SecretsManager instance.
  • serviceClass: a string that identifies the service class in the AWS SDK to use, e.g. SecretsManager

Example Usage

An API Controller using waitsForEmptyEventLoop, service middleware.

-- todo.js --
// define the API controller for 'todo' records.

const { framework } = require('lessware')
const aws = require('lessware-aws')
const databaseConnection = require('./db-setup')

module.exports = framework([

  // tell lambda to return before all connections are closed
  aws.waitsForEmptyEventLoop(),

  // attach `secrets` to `context.aws`
  aws.service({
    serviceName: 'secrets',
    serviceClass: 'SecretsManager'
  }),

  // example middleware to cache db connection
  async context => {
    // assumes `context.db` exists
    if (!context.db.client) {
      // use the `aws.secrets` service
      const url = await context.aws.secrets.getSecretValue('db-url')
      context.db.client = await databaseConnection(JSON.parse(url.SecretString))
    }
    return context
  },

  // example controller using cached database client
  async context => {
    const doc = await context.db.client.getRecord("todos", event.payload.id)
    return {
      statusCode: 200,
      body: JSON.stringify(doc),
    }
  }
])


// -- index.js --
const todo = require('./todo')
const router = {todo}

// persist connections setup by middleware
const db = {}

exports.handler = async (event, ctx) => {
  const controller = router[event.fieldName]

  // invoke the controller that takes one object for framework "context"
  return controller({event, ctx})
}

Maintainers

When buidling releases,

1. npm test
2. git checkout -b feature-branch
3. git commit -m "your message"
4. bump version
   1. npm version patch
   2. npm version minor
5. npm publish