class Faraday::Adapter::EMHttp

def perform_request(env)
  if parallel?(env)
    manager = env[:parallel_manager]
    manager.add {
      perform_single_request(env).
        callback { env[:response].finish(env) }
    }
  else
    unless EventMachine.reactor_running?
      error = nil
      # start EM, block until request is completed
      EventMachine.run do
        perform_single_request(env).
          callback { EventMachine.stop }.
          errback { |client|
            error = error_message(client)
            EventMachine.stop
          }
      end
      raise_error(error) if error
    else
      # EM is running: instruct upstream that this is an async request
      env[:parallel_manager] = true
      perform_single_request(env).
        callback { env[:response].finish(env) }.
        errback {
          # TODO: no way to communicate the error in async mode
          raise NotImplementedError
        }
    end
  end
rescue EventMachine::Connectify::CONNECTError => err
  if err.message.include?("Proxy Authentication Required")
    raise Error::ConnectionFailed, %{407 "Proxy Authentication Required "}
  else
    raise Error::ConnectionFailed, err
  end
rescue => err
  if defined?(OpenSSL) && OpenSSL::SSL::SSLError === err
    raise Faraday::SSLError, err
  else
    raise
  end
end