code: @Override
    public boolean persistState() {
      if (!safeMode) {
        LOG.info(
          "Cannot persist state because ClusterManager is not in Safe Mode");
        return false;
      }
  
      try {
        JsonGenerator jsonGenerator = CoronaSerializer.createJsonGenerator(conf);
        jsonGenerator.writeStartObject();
  
        jsonGenerator.writeFieldName("startTime");
        jsonGenerator.writeNumber(startTime);
  
        jsonGenerator.writeFieldName("nodeManager");
        nodeManager.write(jsonGenerator);
  
        jsonGenerator.writeFieldName("sessionManager");
        sessionManager.write(jsonGenerator);
  
        jsonGenerator.writeFieldName("sessionNotifier");
        sessionNotifier.write(jsonGenerator);
  
        jsonGenerator.writeEndObject();
        jsonGenerator.close();
      } catch (IOException e) {
        LOG.info("Could not persist the state: ", e);
        return false;
      }
      return true;
    }
docs: This function saves the state of the ClusterManager to disk.
  @return A boolean. True if saving the state succeeded, false otherwise.