深入解析yarn架构设计与技术实现-事件库与状态机

protected void dispatch(Event event) {
   //all events go thru this loop
   if (LOG.isDebugEnabled()) {
     LOG.debug("Dispatching the event " + event.getClass().getName() + "."
         + event.toString());
   }
   Class<? extends Enum> type = event.getType().getDeclaringClass();
   try{
     EventHandler handler = eventDispatchers.get(type);
     if(handler != null) {
       handler.handle(event);
     } else {
       throw new Exception("No handler for registered for " + type);
     }
   } catch (Throwable t) {
     //TODO Maybe log the state of the queue
     LOG.fatal("Error in dispatcher thread", t);
     // If serviceStop is called, we should exit this thread gracefully.
     if (exitOnDispatchException
         && (ShutdownHookManager.get().isShutdownInProgress()) == false
         && stopped == false) {
       Thread shutDownThread = new Thread(createShutDownThread());
       shutDownThread.setName("AsyncDispatcher ShutDown handler");
       shutDownThread.start();
     }
   }
 }