org.apache.flink.runtime.state

Interface KvStateSnapshot<K,N,S extends org.apache.flink.api.common.state.State,SD extends org.apache.flink.api.common.state.StateDescriptor<S,?>,Backend extends AbstractStateBackend>

Type Parameters:

K - The type of the key

N - The type of the namespace

S - The type of the State

SD - The type of the StateDescriptor

Backend - The type of the backend that can restore the state from this snapshot.

All Superinterfaces:

AutoCloseable, Closeable, Serializable, StateObject

All Known Implementing Classes:

AbstractFsStateSnapshot, AbstractMemStateSnapshot, AsynchronousKvStateSnapshot, FsFoldingState.Snapshot, FsListState.Snapshot, FsReducingState.Snapshot, FsValueState.Snapshot, MemFoldingState.Snapshot, MemListState.Snapshot, MemReducingState.Snapshot, MemValueState.Snapshot

public interface KvStateSnapshot<K,N,S extends org.apache.flink.api.common.state.State,SD extends org.apache.flink.api.common.state.StateDescriptor<S,?>,Backend extends AbstractStateBackend>
extends StateObject

This class represents a snapshot of the KvState, taken for a checkpoint. Where exactly the snapshot stores the snapshot data (in this object, in an external data store, etc) depends on the actual implementation. This snapshot defines merely how to restore the state and how to discard the state.

One possible implementation is that this snapshot simply contains a copy of the key/value map.

Another possible implementation for this snapshot is that the key/value map is serialized into a file and this snapshot object contains a pointer to that file.

Method Summary

Modifier and Type	Method and Description
KvState<K,N,S,SD,Backend>	restoreState(Backend stateBackend, org.apache.flink.api.common.typeutils.TypeSerializer<K> keySerializer, ClassLoader classLoader) Loads the key/value state back from this snapshot.

Methods inherited from interface org.apache.flink.runtime.state.StateObject

discardState, getStateSize

Methods inherited from interface java.io.Closeable

close

Method Detail

restoreState

KvState<K,N,S,SD,Backend> restoreState(Backend stateBackend,
                                       org.apache.flink.api.common.typeutils.TypeSerializer<K> keySerializer,
                                       ClassLoader classLoader)
                                throws Exception

Loads the key/value state back from this snapshot.

Parameters:

stateBackend - The state backend that created this snapshot and can restore the key/value state from this snapshot.

keySerializer - The serializer for the keys.

classLoader - The class loader for user-defined types.

Returns:

An instance of the key/value state loaded from this snapshot.

Throws:

Exception - Exceptions can occur during the state loading and are forwarded.