Checkpoint statistics contain the duration of a checkpoint, measured as from the CheckpointCoordinator's start to the point when the acknowledge message came.
We should additionally expose
- duration of the synchronous part of a checkpoint
- duration of the asynchronous part of a checkpoint
- number of bytes buffered during the stream alignment phase
- duration of the stream alignment phase
Note: In the case of using at-least once semantics, the latter two will always be zero.