code: public void stop() {
      syncLock.lock();
      try {
        if (syncThread == null) {
          return;
        }
        instanceChangeStreamListener.stop();
        syncThread.interrupt();
        try {
          syncThread.join();
        } catch (final InterruptedException e) {
          return;
        }
        syncThread = null;
        isRunning = false;
      } finally {
        syncLock.unlock();
      }
    }
docs: Stops the background data synchronization thread.