BarrierTransceiver (flink-runtime 0.9.0-milestone-1 API)

```
public interface BarrierTransceiver
```
A BarrierTransceiver describes an operator's barrier checkpointing behavior used for fault tolerance. In the most common case [[broadcastBarrier]] is being expected to be called periodically upon receiving a checkpoint barrier. Furthermore, a [[confirmBarrier]] method should be implemented and used for acknowledging a specific checkpoint checkpoint.

All Methods Instance Methods Abstract Methods
Modifier and Type	Method and Description
`void`	`broadcastBarrierFromSource(long barrierID)` A callback for notifying an operator of a new checkpoint barrier.
`void`	`confirmBarrier(long barrierID)` A callback for confirming that a barrier checkpoint is complete

Interface BarrierTransceiver