Rumbda basics (tl;dr)

index.js

const exec = require('child_process').exec;

exports.handler = function(event, context, callback) {
  const child = exec('./ruby_wrapper ' + "'" +  JSON.stringify(event) + "'", (error, stdout, stderr) => {
    callback(null, JSON.parse(stdout));
  });

  child.stdout.on('data', console.log);
  child.stderr.on('data', console.error);
};

main.rb

# Example usage:

# require 'httparty'
# response = HTTParty.get('https://raw.githubusercontent.com/kleaver/rumbda/master/example/main.rb')

# puts "Access environment variables via ENV: #{ENV['AWS_REGION']}"

# eg. access the `event` that triggered the Lambda execution —
# puts "Access the event via JSON.parse(ARGV.first): #{JSON.parse(ARGV.first)}"

require 'json'
print JSON.generate({"hello"=>"world"})

ruby_wrapper.sh

#!/bin/bash
set -e

# Figure out where this script is located.
SELFDIR="`dirname \"$0\"`"
SELFDIR="`cd \"$SELFDIR\" && pwd`"

# Tell Bundler where the Gemfile and gems are.
export BUNDLE_GEMFILE="$SELFDIR/vendor/Gemfile"
unset BUNDLE_IGNORE_CONFIG

# Run the actual app using the bundled Ruby interpreter, with Bundler activated.
exec "$SELFDIR/ruby/bin/ruby" -rbundler/setup "$SELFDIR/source/main.rb" "$@"