org.apache.flink.runtime.state.KvState Maven / Gradle / Ivy
/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.flink.runtime.state;
import org.apache.flink.api.common.state.State;
import org.apache.flink.api.common.state.StateDescriptor;
/**
* Key/Value state implementation for user-defined state. The state is backed by a state
* backend, which typically follows one of the following patterns: Either the state is stored
* in the key/value state object directly (meaning in the executing JVM) and snapshotted by the
* state backend into some store (during checkpoints), or the key/value state is in fact backed
* by an external key/value store as the state backend, and checkpoints merely record the
* metadata of what is considered part of the checkpoint.
*
* @param The type of the key.
* @param The type of the namespace.
* @param The type of {@link State} this {@code KvState} holds.
* @param The type of the {@link StateDescriptor} for state {@code S}.
* @param The type of {@link AbstractStateBackend} that manages this {@code KvState}.
*/
public interface KvState, Backend extends AbstractStateBackend> {
/**
* Sets the current key, which will be used when using the state access methods.
*
* @param key The key.
*/
void setCurrentKey(K key);
/**
* Sets the current namespace, which will be used when using the state access methods.
*
* @param namespace The namespace.
*/
void setCurrentNamespace(N namespace);
/**
* Creates a snapshot of this state.
*
* @param checkpointId The ID of the checkpoint for which the snapshot should be created.
* @param timestamp The timestamp of the checkpoint.
* @return A snapshot handle for this key/value state.
*
* @throws Exception Exceptions during snapshotting the state should be forwarded, so the system
* can react to failed snapshots.
*/
KvStateSnapshot snapshot(long checkpointId, long timestamp) throws Exception;
/**
* Disposes the key/value state, releasing all occupied resources.
*/
void dispose();
}