Event machine

handler.rb

# frozen_string_literal: true
require 'redis'

class Handler
  DB = Redis.new
  
  def initialize(headers, client)
    @headers = headers
    @client = client
  end

  def handle
    request = @headers.first
    method, full_path = request.split(' ')
    path = full_path.split('?').first
    raise unless method == 'GET' && path =~ %r{^/[0-9]+$}
    id = path[1..-1]
    data = DB.get(id)
    raise unless data
    print 200, data
  rescue
    print 404, 'Not Found'
  ensure
    @client.close_connection_after_writing
  end

  def print(code, text)
    @client.send_data "HTTP/1.1 #{code}\r\n"
    @client.send_data "Content-Type: text/plain\r\n"
    @client.send_data "Content-Length: #{text.length}\r\n"
    @client.send_data "Connection: close"
    @client.send_data "\r\n"
    @client.send_data text
  end
end

server.rb

# frozen_string_literal: true
require 'eventmachine'
require './handler'

class Server < EM::P::HeaderAndContentProtocol
  def receive_request(headers, content)
    Handler.new(headers, self).handle
  end
end

port = ENV['PORT'] || 10_000
EM.run { EM.start_server 'localhost', port, Server }