StateSnapshot (Flink : 2.0-SNAPSHOT API)

All Known Subinterfaces:

IterableStateSnapshot<K,N,S>

All Known Implementing Classes:

CopyOnWriteStateTableSnapshot, HeapPriorityQueueStateSnapshot
```
@Internal
public interface StateSnapshot
```
General interface for state snapshots that should be written partitioned by key-groups. All snapshots should be released after usage. This interface outlines the asynchronous snapshot life-cycle, which typically looks as follows. In the synchronous part of a checkpoint, an instance of StateSnapshot is produced for a state and captures the state at this point in time. Then, in the asynchronous part of the checkpoint, the user calls getKeyGroupWriter() to ensure that the snapshot is partitioned into key-groups. For state that is already partitioned, this can be a NOP. The returned StateSnapshot.StateKeyGroupWriter can be used by the caller to write the state by key-group. As a last step, when the state is completely written, the user calls release().

Nested Class Summary

Nested Classes
Modifier and Type Interface Description

static interface StateSnapshot.StateKeyGroupWriter
Interface for writing a snapshot that is partitioned into key-groups.

Method Summary

All Methods Instance Methods Abstract Methods
Modifier and Type	Method	Description
`StateSnapshot.StateKeyGroupWriter`	`getKeyGroupWriter()`	This method returns `StateSnapshot.StateKeyGroupWriter` and should be called in the asynchronous part of the snapshot.
`StateMetaInfoSnapshot`	`getMetaInfoSnapshot()`	Returns a snapshot of the state's meta data.
`void`	`release()`	Release the snapshot.

- Method Detail
  - getKeyGroupWriter
```
@Nonnull
StateSnapshot.StateKeyGroupWriter getKeyGroupWriter()
```
    This method returns StateSnapshot.StateKeyGroupWriter and should be called in the asynchronous part of the snapshot.
  - getMetaInfoSnapshot
```
@Nonnull
StateMetaInfoSnapshot getMetaInfoSnapshot()
```
    Returns a snapshot of the state's meta data.
  - release
```
void release()
```
    Release the snapshot. All snapshots should be released when they are no longer used because some implementation can only release resources after a release. Produced StateSnapshot.StateKeyGroupWriter should no longer be used after calling this method.