ExecutionPlanStoreWatcher (Flink : Runtime 2.1.1 API)

All Known Implementing Classes:

NoOpExecutionPlanStoreWatcher, ZooKeeperExecutionPlanStoreWatcher
```
public interface ExecutionPlanStoreWatcher
```
A watcher on ExecutionPlanStore. It could monitor all the changes on the execution plan store and notify the ExecutionPlanStore via ExecutionPlanStore.ExecutionPlanListener.
Important: The ExecutionPlanStoreWatcher could not guarantee that there is no ExecutionPlanStore.ExecutionPlanListener callbacks happen after stop(). So the implementor is responsible for filtering out these spurious callbacks.

Method Summary

All Methods Instance Methods Abstract Methods
Modifier and Type	Method	Description
`void`	`start(ExecutionPlanStore.ExecutionPlanListener executionPlanListener)`	Start the watcher on `ExecutionPlanStore`.
`void`	`stop()`	Stop the watcher on `ExecutionPlanStore`.

- Method Detail
  - start
```
void start(ExecutionPlanStore.ExecutionPlanListener executionPlanListener)
    throws Exception
```
    Start the watcher on ExecutionPlanStore.
    
    Parameters:
    
    executionPlanListener - use executionPlanListener to notify the DefaultExecutionPlanStore
    
    Throws:
    
    Exception - when start internal services
  - stop
```
void stop()
   throws Exception
```
    Stop the watcher on ExecutionPlanStore.
    
    Throws:
    
    Exception - when stop internal services