AsyncDispatcher may overloaded with RMAppNodeUpdateEvent when Node is connected/disconnected

  public void handle(NodesListManagerEvent event) {
    RMNode eventNode = event.getNode();
    switch (event.getType()) {
    case NODE_UNUSABLE:
      LOG.debug(eventNode + " reported unusable");
      unusableRMNodesConcurrentSet.add(eventNode);
      for(RMApp app: rmContext.getRMApps().values()) {
        this.rmContext
            .getDispatcher()
            .getEventHandler()
            .handle(
                new RMAppNodeUpdateEvent(app.getApplicationId(), eventNode,
                    RMAppNodeUpdateType.NODE_UNUSABLE));
      }
      break;
    case NODE_USABLE:
      if (unusableRMNodesConcurrentSet.contains(eventNode)) {
        LOG.debug(eventNode + " reported usable");
        unusableRMNodesConcurrentSet.remove(eventNode);
      }
      for (RMApp app : rmContext.getRMApps().values()) {
        this.rmContext
            .getDispatcher()
            .getEventHandler()
            .handle(
                new RMAppNodeUpdateEvent(app.getApplicationId(), eventNode,
                    RMAppNodeUpdateType.NODE_USABLE));
      }
      break;
    default:
      LOG.error("Ignoring invalid eventtype " + event.getType());
    }
  }