code: @Override
    public void busy(long time)
    {
      getRequestBusyProbe().start();
  
      synchronized (this) {
        degrade(time);
        
        _lastBusyTime = time;
        _firstSuccessTime = 0;
  
        _currentFailCount++;
  
        _busyCountTotal++;
  
        _state = _state.toBusy();
      }
    }
docs: Called when the server responds with "busy", e.g. HTTP 503