code: public final void shutdown() {
  		try {
  			onComplete();
  			executor.shutdown();
  			requestTaskExecutor.shutdown();
  		}
  		catch (Throwable t) {
  			onError(Operators.onOperatorError(t, currentContext()));
  		}
  	}
docs: Shutdown this active {@code Processor} such that it can no longer be used. If the resource carries any work, it
  will wait (but NOT blocking the caller) for all the remaining tasks to perform before closing the resource.