[YARN-2030] Use StateMachine to simplify handleStoreEvent() in RMStateStore

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 2.5.0
• Target Version/s: 2.5.0
• Hadoop Flags: Reviewed
• Assignee: Binglin Chang
• Reporter: Junping Du
• Created: 08/May/14 09:28
• Updated: 25/Oct/19 20:26
• Resolved: 09/Jun/14 19:47

Description

Now the logic to handle different store events in handleStoreEvent() is as following:

if (event.getType().equals(RMStateStoreEventType.STORE_APP)
        || event.getType().equals(RMStateStoreEventType.UPDATE_APP)) {
      ...
      if (event.getType().equals(RMStateStoreEventType.STORE_APP)) {
        ...
      } else {
        ...
      }
      ...
      try {
        if (event.getType().equals(RMStateStoreEventType.STORE_APP)) {
          ...
        } else {
          ...
        }
      } 
      ...
    } else if (event.getType().equals(RMStateStoreEventType.STORE_APP_ATTEMPT)
        || event.getType().equals(RMStateStoreEventType.UPDATE_APP_ATTEMPT)) {
      ...
      if (event.getType().equals(RMStateStoreEventType.STORE_APP_ATTEMPT)) {
        ...
      } else {
        ...
      }
        ...
        if (event.getType().equals(RMStateStoreEventType.STORE_APP_ATTEMPT)) {
          ...
        } else {
          ...
        }
      }
      ...
    } else if (event.getType().equals(RMStateStoreEventType.REMOVE_APP)) {
    ...
    } else {
      ...
    }
}

This is not only confuse people but also led to mistake easily. We may leverage state machine to simply this even no state transitions.