Wool js

A wrapper for AWS Lambda functions adding an async handler for better function structure, a customizable logger, and better exception handling. More to come soon!

Works great with shep!

Why do you need this?

AWS Lambda is growing in popularity as a way to build functions for anything from serving web applications to moving massive amounts of logs between amazon services. Wool lets you build those functions without having to add logic for the features Wool covers every time you build an API or a custom lambda function.

Note: Wool does not run or build your functions or enable local testing. See shep for details on building and running functions!

Getting Started

Prerequisites

It will be helpful to have some existing experience with API gateway and Lambda. If you have never used either of these tools before, it is recommended to setup a function manually to see how things are done. Please refer to Amazon's own getting started guide

Installation

npm install wooljs

Wooljs uses async/await functions. You will need to install a babel-preset that enables these functions, like babel-preset-stage-3 or a plugin for async/await

Features

Logger

your-lambda-function.js

import { log } from 'wooljs'

log.info('wool is cool!')

will log:

{"time":"2014-05-18T23:47:06.545Z","functionName":"your-lambda-function","functionVersion":27374,"level":"info","name":"mymodule","message":"Starting mymodule#handler()"}

Wool's logger uses the log level declared in process.env.LOG_LEVEL (defaults to info), one of 4 levels with corresponding methods: log.debug(), log.info(), log.warn(), log.error()

For more details see the shep-logger repo

Async handler

your-lambda-function.js

import { asyncHandler } from 'wooljs'

export const handler = asyncHandler(

  // context and callback optional, asyncHandler takes care of the callback
  async (event, /* context, callback */) => {

    const foo = 'bar'

    return foo
  }
)

The benefit of the asyncHandler is to remove the overhead of managing callbacks, promise chains, and the context object in a typical AWS Lambda handler function. Simply write the code you need the function to execute, declare its return value and move on with your life.

The asyncHandler function wrapper will also log every event sent through your handler.

Exception handling and notifications

Currently, Wool will throw an error and write the error message to stdout with log.error(), and return callback(error) from the asyncHandler.

Airbrake

To add error notifications via airbrake, simply add AIRBRAKE_PROJECT_KEY and AIRBRAKE_PROJECT_ID to process.env and configure your Airbrake settings for that project. Wool will take care of the rest.

The Airbrake node package needs __dirname: true if you are using webpack.

Timeouts

AWS Lambda does not have the best logging when it comes to timeouts. Your functions will fail after your configured timeout setting, but lambda does not log any recent stack trace or helpful error.

Wool wraps Lambda's default timeout handling and throws an exception with a helpful stack trace and Wool's normal exception logging/notification. This will throw 50ms before your configured timeout duration.

Why the name 'wool'?

Wool is named as a wrapper for lambda functions, keeping with the theme established by shep

Development

Pull requests welcome!

Compile: npm run compile

Publish: npm run pub "publish" is reserved by npm

Linter: We use standard to lint our projects. Travis will run npm run lint for PRs and pushes in lieu of tests for now

bustle / wool

readme