code: @CommandArgument
    public void stop() {
      System.out.println("Stopping worker");
      worker.shutdown();
      workerThread.interrupt();
      try {
        workerThread.join();
      } catch (InterruptedException e) {
        logger.warn("Joining to worker thread interrupted", e);
      }
      worker = null;
      workerThread = null;
      taskProgressStates = null;
    }
docs: Stops the worker process.