Cutlet

In November 2018, Amazon Web Services announced their serverless platform, Lambda, would support Ruby as a runtime.

Ruby has a long tradition of being useful for microservices, with a bunch of excellent Web frameworks built on top of the Rack servlet specification. Wouldn't it be great if developers could drop their existing Rack apps into a Lambda environment with minimal fuss and next-to-no config?

Enter Cutlet!

Installation

Add this line to your application's Gemfile:

gem 'cutlet'

And then execute:

$ bundle

Usage

For general documentation about AWS Lambda with Ruby, check out their documentation.

Setup

Standalone Rack application

In your handler.rb (or whatever you've named it), require your application and serve it with Cutlet:

# handler.rb

require 'cutlet'
require_relative './my_rack_app'

def handler(event:, context:)
  Cutlet.serve(event: event, context: context, app: MyRackApp)
end

That's it!

Custom Rack with config.ru (WIP)

require 'cutlet'

def handler(event:, context:)
  Cutlet.serve(event: event, context: context, rackup: 'config.ru')
end

or do it inline!

require 'cutlet'
require 'rack-attack'

require_relative './my_rack_app'

def handler(event:, context:)
  Cutlet.serve(event: event, context: context) do
	use Rack::Attack
	
	run MyRackApp
  end
end

Interaction with the Lambda environment

All Lambda handlers are provided with an event & a context. These are passed into the environment hash that Rack uses and are accessible by your application from there:

function_name = env['lambda.context'].function_name

Lambda functions have a specific response format, but your app doesn't need to worry about that. Cutlet will take the response your app generated and map it into the correct format automatically!

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake test to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/anicholson/cutlet. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.

License

The gem is available as open source under the terms of the MIT License.

Code of Conduct

Everyone interacting in the Cutlet project’s codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.