code: public void closeAllPlatforms() {
  
      log.log(Level.FINEST, "Closing all Vert.x instances");
      try {
  
        for (Map.Entry<String, Vertx> entry : this.vertxPlatforms.entrySet()) {
          stopVertx(entry.getValue());
        }
        vertxPlatforms.clear();
        vertxHolders.clear();
  
      } catch (Exception e) {
        log.log(Level.SEVERE, "Error closing Vert.x instance", e.getCause());
      }
    }
docs: Stops all started Vert.x platforms.
  
  Clears all vertx holders.