org.apache.flink.runtime.state.StateHandle 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 java.io.Serializable;
/**
* StateHandle is a general handle interface meant to abstract operator state fetching.
* A StateHandle implementation can for example include the state itself in cases where the state
* is lightweight or fetching it lazily from some external storage when the state is too large.
*/
public interface StateHandle extends Serializable {
/**
* This retrieves and return the state represented by the handle.
*
* @param userCodeClassLoader Class loader for deserializing user code specific classes
*
* @return The state represented by the handle.
* @throws java.lang.Exception Thrown, if the state cannot be fetched.
*/
T getState(ClassLoader userCodeClassLoader) throws Exception;
/**
* Discards the state referred to by this handle, to free up resources in
* the persistent storage. This method is called when the handle will not be
* used any more.
*/
void discardState() throws Exception;
/**
* Returns the size of the state in bytes.
*
* If the the size is not known, return 0
.
*
* @return Size of the state in bytes.
* @throws Exception If the operation fails during size retrieval.
*/
long getStateSize() throws Exception;
}