LeaderRetrievalEventHandler (Flink : 2.0-SNAPSHOT API)

All Known Implementing Classes:

DefaultLeaderRetrievalService
```
public interface LeaderRetrievalEventHandler
```
Interface which should be implemented to notify to LeaderInformation changes in LeaderRetrievalDriver.
Important: The LeaderRetrievalDriver could not guarantee that there is no LeaderRetrievalEventHandler callbacks happen after AutoCloseable.close(). This means that the implementor of LeaderRetrievalEventHandler is responsible for filtering out spurious callbacks(e.g. after close has been called on LeaderRetrievalDriver).

Method Summary

All Methods Instance Methods Abstract Methods
Modifier and Type	Method	Description
`void`	`notifyLeaderAddress(LeaderInformation leaderInformation)`	Called by specific `LeaderRetrievalDriver` to notify leader address.

- Method Detail
  - notifyLeaderAddress
```
void notifyLeaderAddress(LeaderInformation leaderInformation)
```
    Called by specific LeaderRetrievalDriver to notify leader address.
    Duplicated leader change events could happen, so the implementation should check whether the passed leader information is truly changed with last stored leader information.
    
    Parameters:
    
    leaderInformation - the new leader information to notify LeaderRetrievalService. It could be LeaderInformation.empty() if the leader address does not exist in the external storage.