health_check.rb

class HealthCheck
  class << self
    def run(port: 8000)
      self.new(port: port).run
    end

    def background(port: 8000)
      self.new(port: port).background
    end
  end

  attr_reader :server, :port, :thread

  def initialize(port: 8000)
    @port = port
    @server = TCPServer.new(port)
  end

  def run
    loop do
      client = server.accept
      client.puts "OK"
      client.close
    end
  end

  def background
    Thread.abort_on_exception = true
    Thread.kill(thread) if thread && thread.alive?

    @thread = Thread.new { run }
  end
end