AM启动--StoreAppAttemptTransition(三)

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StoreAppAttemptTransition(基于hadoop 2.7.6)

     1.将AppAttempt状态存储到共享存储系统
     2.触发RMAppAttemptEventType.ATTEMPT_NEW_SAVED

经过StoreAppAttemptTransition转换处理器后,正常情况RMStateStoreState保持ACTIVE状态不变;发生异常情况下,转换为FENCED状态.在HA模式下ResourceManager切换为standBy,不在HA模式下则快速失败.
代码清单:

	private static class RMStateStore.StoreAppAttemptTransition implements
      MultipleArcTransition<RMStateStore, RMStateStoreEvent,
          RMStateStoreState> {
    @Override
    public RMStateStoreState transition(RMStateStore store,
        RMStateStoreEvent event) {
      if (!(event instanceof RMStateStoreAppAttemptEvent)) {
        // should never happen
        LOG.error("Illegal event type: " + event.getClass());
        return RMStateStoreState.ACTIVE;
      }
      boolean isFenced = false;
      ApplicationAttemptStateData attemptState =
          ((RMStateStoreAppAttemptEvent) event).getAppAttemptState();
      try {
        if (LOG.isDebugEnabled()) {
          LOG.debug("Storing info for attempt: " + attemptState.getAttemptId());
        }
        /**
         * 	将Application和AttemptState存储到共享存储系统(一般为ZKRMStateStore)
         * 	目录结构:
         * 		ROOT_DIR_PATH
			   * |--- RM_APP_ROOT
			   * |     |----- (#ApplicationId1)
			   * |     |        |----- (#ApplicationAttemptIds)
			   * |     |
			   * |     |----- (#ApplicationId2)
			   * |     |       |----- (#ApplicationAttemptIds)
			   */
			   store.storeApplicationAttemptStateInternal(attemptState.getAttemptId(),
            attemptState);
          /**
         * 	触发RMAppAttemptEventType.ATTEMPT_NEW_SAVED
         */
        store.notifyApplicationAttempt(new RMAppAttemptEvent
               (attemptState.getAttemptId(),
               RMAppAttemptEventType.ATTEMPT_NEW_SAVED));
      } catch (Exception e) {
        LOG.error("Error storing appAttempt: " + attemptState.getAttemptId(), e);
        /**
         * 	出现异常情况的时候,在HA的情况下转为StandBy或在没有HA的情况下快速失败
         */
        isFenced = store.notifyStoreOperationFailedInternal(e);
      }
      return finalState(isFenced);
    };
  }