Ruby Queue

I wanted to build a simple queue that could accept HTTP requests to enqueue and dequeue, to keep things simple enough to post via a curl command. With Ruby being my go-to language for hobby projects, I wrote this:

require 'sinatra'

$queue = []

get '/' do
  if $queue.length == 0
    status 404
    content_type('text/plain')
    return 'EMPTY'
  end
  content_type('application/json')
  $queue.shift
end

post '/' do
  if request.content_type != 'application/json'
    status 500
    content_type('text/plain')
    return 'ERROR'
  end
  $queue.push request.body.read
  content_type('text/plain')
  'OK'
end

The POST handler takes in the body of a request with HTTP request content type “application/json” and appends it to an array.
The GET handler removes the item from the queue and returns it as the body of the HTTP response content type “application/json”.
If the array is empty, the GET handler returns a 404 with an EMPTY message sent with HTTP response content type “text/plain”.

To run the above, save it within main.rb, then gem install sinatra and ruby main.rb. By default, Sinatra listens on the localhost port 4567. To change this, set :bind, '0.0.0.0' and set :port, 8080 in the Ruby code. If you are using this for anything more than throw-away code or a prototype, make the bind IP and port configurable, add authentication, and even TLS/SSL.