code: @Override
      public void setManual() {
        this.threshold = 1.5f; // this threshold can never be reached
        this.extension = Long.MAX_VALUE;
        this.replQueueThreshold = 1.5f; // can never be reached
        this.reached = -1;
        enter();
        reportStatus("STATE* Safe mode is ON.", true);
      }
docs: Enter safemode manually.
  <p/>
  The {@link #threshold} is set to 1.5 so that it could never be reached.
  {@link #namesystem.getTotalBlocks()} is set to -1 to indicate that safe
  mode is manual.