code: public synchronized void onRequestFailed(String message, Throwable ex) {
  		String reason = message + ": " + ex.getClass().getName() + ": " + ex.getMessage();
  		allRequestsTracker.onRequestFailed(reason);
  		recentRequestsTracker.onRequestFailed(reason);
  		meter.mark();
  	}
docs: Registers a failed request.